CA2466577A1 - Heart assist system - Google Patents

Abstract

An extracardiac pumping system (10) for supplementing the circulation of blood, including the cardiac output, in a patient without any component thereof being connected to the patient's heart. One embodiment and application of the extracardiac system comprises a pump (32) that may be implanted subcutaneously at or about the patient's femoral artery in a minimally-invasive procedure, wherein the pump is powered by a battery (44) and a mechanism for charging the battery extracorporeally, whereby the pump draws blood through an inflow conduit (50) fluidly coupled to the patients femoral artery via, for example, a subcutaneous anastomosis connection, and discharges blood through an outflow conduit (52) fluidly coupled to a second peripheral artery via, for example, a subcutaneous anastomosis connection. The pump may be operated in continuous flow mode, or in a pulsatile fashion synchronous with the patient's heart, thereby potentially reducing the afterload of the heart.
The conduits (50, 52) can be placed in fluid communication with a multi-lumen catheter (510) for single point application of the system to the patient. If desired, a reservoir (410) may be provided fluidly communicating with the inflow conduit. The system may also comprise a device (402) for maintaining at or near body temperature the blood travelling extracorporeally within the system . If further desired the present system may be carried directly on the patient with a device (610) that holds at least the pump and is carried by a belt or a shoulder strap.

Description

HEART ASSIST SYSTEM .
Field Of The Invention The present inveM'ron relates generaAy to a system for assistkrg the heart a<rd, in partiwtar, to an extracardiac pumping system and a method for both supplementing the circulation of blood through the patient and for enhancing vascular blood mixing using a minimally invasive procedure.
Background Of The Invention During the last decade, congestive heart falun: ICHF1 has burgeoned into the most important public health problem in cardiovascular meddne. As reported in Glum, R. F., Epidemiology of Heart far7ure a~ the U. S. 126 Am. Heart J. 1042 (1993), four hundred thousand (400,000) new cases of CHF are diagnosed ~ the United States amuaAy. The disorder is said to affect nearly 5 nu'~on people in this country and close to 20 mllion people worldwide. The number of hospitalizations for CHF has increased more than three fokf in the fast 15 years. Urdortunately, nearly 250,000 patients die of heart failure amuaAy. Axo~ng to the Frarnurgh~rt Heart Study, the 5-year mortafrty rate for patients with congestive heart failure was 75 per cent in men and Gl per cent in women (Ho, K. K. L, Anderson, K. M., Kennel. W. B., et al., Scwival ARer the Onset of Congestive Heart fa~7ure in framingham Heart Study Subject, 88 Circulation 107 [19931). This disorder represents the most common d'rscharge diagnosis for patients over 65 years of age. Although the incidence of most cardiovascular ~sorders has deaeas~ over the past 10 to 20 years, the incidence and prevalence of congPxtive heart failure has inueased at a dramatic rate. This number will increase as patients who would normally fu; of an awte myocardial infarction Iiteart attack) survive, and as the population ages.
CHF manifests'rtself primarly by exertional dyspnea (diffiadt or labored breathing) and fatigue. Three paradigms are used to __ describe the causes and therapy of CHF. The first views this condition in temrs of altered pump function and abnormal arculatory dynamics. Other models descr~e it largely n terms of altered myoca~al ceNular perfomrartce or of altered gene expression in the tx:As of the atrophied heart. In its broadest sense. CHF can be defined as the inabl'rty of the heart to pump bkwd throughout the body at the rate needed to maintain adequate blood flow, and many of the normal functior>,c of the body.
To address CHF, many types of cardiac assist devices have been developed. A
cardiac or circulatory assist device is one that aids the fat~ing heart by creasing its pumping function or by allowing 'tt a certain artaunt of rest to tecova 'tts pumping function.
Because congestive heart failure may be chronic or acute, different categories of heart assist devices exist. Short of a heart traruplant, at least two types of chronic heart assist systems have been developed. One type ~nploys a ful or partial prosthetic corrected between the heart and the aorta, ors example of which is commonly referred to as a LIIAD - Left Ventricular Assist Device. Wdit reference to Figure 1 herein, one example of a L11AD 2 is shown. The LYAD
comprises a pump and assodated valves 4 that draws blood directly from the apex of the left ventricle 6 and directs the blood to the aortic arch 8. bypassing the aortic valve. In this application, the left ventricle stops functioning and does not contract or expand. The left verrtride becomes, in effect, an extension d~the left atrium, with the IVAD 2 taking over for the left ventricle. The ventride, thus, becomes a low-pross<rre chamber. Because the intent is to take over for the left ventricle, the LOAD operates by pumping blood at carf~ac rates. With an LIfAD, oxygenated blood circulation is established sufficient to satisfy the demand of the patient's organs. Under these ciraarutances, however, contirutous flow may not be desired because the patient's arterial system is deprived of pulsatile wave flow, which is beneficial to certain parts of the patient.
Another type of chronic heart assist system is shown in U. S. Patent No.
5,267,940 to Mouhfer. Moulder descrlres a pump implanted into the proximal descending aorta to assist in the circulation of blood through the aorta. Because it is intended to pump blood flowing directly out of the heart, it is important that the Moulder device operate in a properly timed, pulsatile fashion. If it is not operated in direct synchronization with the patient's hears, there is a risk that the pump might cause 'carotid steal phenomenon' where blood is drawn away from the patient's brain through the carotid arteries when there is insufficient blood in the left ventricle.
In addressing acute CNF, two types of heart assist devices have bean used. One is counterpulsatory in nature and is exempffied by an intro-aortic balloon pump (IABP). Wrth an IABP, the balloon is collapsed during isovolumic contraction, providing a reduced pressure against which the heart must pump blood, thereby reducing the load on the heart during systole. The balloon is then expanded, forcing blood ormiditectionally through the arterial system- Another example of this first type employs one or more collapsble chambers in which blood flows passively into the chamber during systole, as is shown in U. S. Patent No. 4,240,409 to Robinsan et al. The chamber is then collapsed and the blood forabiy returned to the aorta. These devices simulate a chamber of the heart and depend upon an inflatable bladder to effectuate pumping action, requiring an external pneumatic driver. Moreover, they do not operate as a continuous flow system, operating exclusively in pulsatile fashion.
A second type of acute assist device utifaes an extracorporeal pump, such as the B'romedicus cerrtrifugal pump, to direct blood through the patient whle surgery is parfom~ed on the heart. In one example, described in U. S. Patent No. 4,968,293 to Nelson, the heart assist system employs a centrifugal pump in which the muscle of the patient is utilized to add pulsattlity to the blood flow.
The Nelson device is used to bypass a portion of the descending aorta.
Another device, shown in U. S. Patent No. 4,080,958 to Bregman et al., utilizes an inflatable and collapsible bladder to assist in blood perfusion dufmg heart trauma and is intended to supplement a conventional heart-lung machine by imparting pulsatile actuation. In the primary embodiment disclosed in Bregman, the balloon is controlled to maintain suffiaerd pressure at the aortic root during diastole to ensure sufficient blood perfusion to the coronary arteries.
In an alternative embodiment, a low resistance outlet from the aorta to the inferior vena cava is provided to reduce the aortic pressure during systole, thus, reduang the hemodynamic load on the left ventricle.
Other devices, such as that shown in U. S. Patent Nn. 4,034,742 to Thoma, depend upon interaction and coordination with a mechanical pumping chamber containing a movable pumping diaphragm. These devices are intended primarily for application proximate the heart and within the patient's thorax, requiring major invasive surgery.
Other devices are shown in UK Application, GB 2,174,151A, which discloses a blood retroperfusion system, U.S. Patent No.

2,935,068 to Donaldson, which discloses a blood circulating system, and WO
98J14225, which discloses a circulatory support system.
Many CNF devices are acutely used in the perioperative per'rod. For example, U. S. Patent No. 4,995,857 to Amold discloses a perioperative device to pump blood at essentially cardiac rates during surgery when the heart has fated or has been stopped to perform cardac surgery. The Amold system temporarily replaces the patient's heart and lung and pumps blood at cardiac rates, typically 5 to 6 literslmin. ~'ke aft systems that bypass the heart and the lungs, an oxygenator is required. Of course, with any system that includes an oxygenator, such as the conventional heart-lung machine, the patient cannot be ambulatory.
With early IABP devices, a polyurethane balloon was mounted on a vascular catheter, inserted into the femoral artery, and positioned in the descending aorta just distal to the left subclavian artery.
The balloon catheter was connected to a pump console that pumped helium or carbon dioxide into the balloon during diastole to inflate it. During isovolumic contraction, i. e., during the brief Time that the aortic valve is closed and the left ventricle continues to contract, the gas used to actuate the balloon was rapidly withdrawn to deflate the balloon. This reduced the pressure at the aortic root when the aortic valve opened. In contrast, during diastole, the balloon was inflated, causing the diastolic pressure to rise and pushing the blood in the aorta distally towards the lower part of the body (on one side of the balloon) and prox'imalty toward the heart and into the coronary arteries Ion the other).

The major advantage in such a couMerpulsation device was systolic deflation, which lowered the intro-aortic volume and pressure, reducing both aftedoad and myocardial oxygen consumption. In other words, when the balloon is inflated, rt creates an artificiany higher pressure in the aorta, which has the ancllary benefit of greater perfusion through the coronary arteries. When the balloon deflates, just before the aortic valve opus. the pressure and voliune of the aorta decrease, relieving some of the hemodynamic S burden on the heart. These physiologic responses improved the patierrt's cardiac output and coronary circulation, temporarily arrproving hemodynamirx. In general, counterpulsation with an IABP can augment cardiac output by about 15%, this being frequently sufficient to stabilize the patient's hemodynamic status, which might otherwise rapidly deteriorate. When there is evidence of more efficient pumping ab7ity by the heart, and the patient has moved to an enproved doss of hetnodynamic status, counterpuisatian can be discorrtinued, by slowly weaning while monitoring for deterioration.
IO Until 1979, a!I IABP catheters were inserted via surgical cutdown, generally of the femoral artery. Srcrce then, the development of a percutaneous IABP catheter has allowed quicker, and perhaps safer, insertion and has resulted in more expeditious institution of therapy and expansion of clinical applications. Inflation and deflation of the balloon, however, requires a pneumatic pump that is sufficiently large that it must be employed extracorpareally, thereby restricting the patient's movements and ability to carry out normal, daily activities. IABP devices are, thus, limited to short term use, on the order of a few days to a fsw weeks.
I S As discussed above, a variety of ventricular assist pumping mechanisms have been designed. Typically associated with LVADs are valves that are used in the inlet and outlet conduits to insure unidirectional blood flow. Given the close proximity of the heart, unidirectional flow was necessary to avoid inadvertent backflaw into the heart. The use of such valves also minimized the thrombogenic potential of the LVAD device.
Typically, the pump associated with older LVADs was a bulky pulsatile flow pump, of the pusher place or diaphragm style, 20 such as those manufactured by Baxter Novacor or TCI, respectively. Given that the pump was implanted within the chest andlor abdominal cavity, major invasive surgery was required. The pumps were typically driven through a percutaneous driveline by a portable external console that monitors and reprograms functions.
Altemativety, rotary pumps, such as centrifugal or axial pumps, have been used in heart assist systems. With centrifugal pumps, the blood enters and exits the pump practically in the same plane. An axial pump, in contrast, directs the blood along the axis of 25 rotation of the rotor. Inspired try the Archimedes screw, one design of an axial pump has been miniaturized to about the size of a pencil eraser, although other designs are larger. Despite its small size, an axial pump may be sufficiently powerful to produce flows that approach those used with older LVADs. Even with miniaturized pumps, however, the pump is typically introduced into the left ventricle through the aortic valve or through the apex of the heart, and its function must be controlled from a console outside the body through percutaneous lines.
30 All of these heart assist systems referred to above serve one or both of two objectives: (1) to improve the perfomrance of a patient's operative~but-diseased heart from the mirirtnum, classified as NYHAC
Class IV, to practically normal, classfied as t or D; or i21 to supplement oxygenated blood c'rcculation through the patient to satisfy organ dernartd when the patient's heart is suffering from CHF.
With such systems, extreme pumping and large amounts of energy, volume, and heat dissipation are required.
Many of these heart assist systems have severe! genera! features in common: 1 / the devices are cardiac in nature; i. e., 35 they era placed directly within or adjacent to the heart, or within one of the primary vessels associated with the heart !aortal, and are often attached to the heart andlor aorta; 21 the devices attempt to reproduce pulsatile blood flow naturally found in the mammalian circulatory system and, therefore, require valves to prevent backflow; 31 the devices are driven from external consoles, often triggered 6y the electrocardiogram of the patient; and 4i the size of the blood pump, including its associated connectors and accessories, is generally unmanageable within the anatomy and physiology of the recipient. Due to having one or more of these features, the prior art heart assist devices are limited in their effectiveness and/or practicality.
Many of the above identified prior art systems, generally referred to as Mechanical Circulatory Assist Devices, are not the only means, however, used to treat patients with congestive heart failure (CHFI. Mast CHF patients are prescribed as many as five to seven different drugs to ameliorate their signs and symptoms. These drugs may include diuretics, angiotensin converting enzyme (ACE) inhibitors, beta-blockers, cardiac glycosides, and peripheral vasodilators. The rationale for pharmacological intervention in heart failure include minimizing the load on the heart, improving the pumping action of the heart 6y enhancing the contractility of the muscle fibers, and suppression of harmful neurohormonal compensatory mechanisms that are activated because of the decreased pumping function of the heart.
Noncompliance with what is often a complex drug regime may dramatically adversely affect the recovery of a CHF
patient leading to the need for hospitalization and possibly morbidity and mortality. In addition, ACE inhibitors and diurectics can cause hypotension, which leads to decreased organ perfusion or an increasing demand on the heart to pump more blood. This leads to an inability, in many cases, to prescribe the most effective dosage of ACE inhibitors and a less than optimum outcome for the patient. Patients suffering from CHF with the underlying cause of mitral valve insufficiency have been able to have their diuretics reduced following surgical repair of their mitral valve. This is due to an increased cardiac output and arterial pressures (as a result of the correction of the problem) resulting in more effective organ perfusion. With the reduction in the use of diuretics and the resultant hypotension, more effective dosages of ACE inhibitors can be used with more favorable outcomes. In addition, it is easier for the patient to follow a less complex drug regime, eliminating the costly and life threatening risks associated with noncompliance.
When blood flow through the coronary arteries falls below the level needed to provide the energy necessary to maintain myocardial function, due often to a blockage in the coronary arteries, a myocardat infarction or heart attack occurs. This is a result of the blockage in the coronary arteries preventing blood from delivering oxygen to tissues downstream of the blockage. The closer the blockage is to the coronary ostia, however, the more severe and life threatening the myocardial infarction. The farther the location of the blockage is from the coronary ostia, the smaller the area of tissue or myocardium that is at risk. As the energy stored in the affected area decreases, myocardial cells begin to die. The larger the an:a that dies due to the loss of oxygen, the more devastating the infarction. To reduce the area at risk, at least two known options are to either increase the oxygen supply to the affected area or decrease the energy demands of the heart to prolong energy stores until the blockage can be removed or reduced. One particular method to increase blood flow, thereby increasing delivery of oxygen to the affected area, is through a technique called retroperfusion.
This is accomplished by passing a cannula into either the right or left ventricle (depending on the area of the blockage) and perfusing oxygenated blood retrograde up the coronary artery on the downstream side of the blockage. Another method is to use drugs to increase the farce of contraction of the myocardium, creating increased blood flow across the blocked area. Yet another method is to use drugs, such as pentoxifylline, aspirin, or TPA (tissue plaminogen activator), to reduce the viscosity of (thin out) the blood, inhibit platelet aggregation, or lyse thrombi (clotsl, respectively, thus, allowing more blood to pass by the blockage. The goal of all of these methods is to increase the delivery of oxygen to the tissue at risk.
3 $ The alternative option mentioned above is to reduce the energy demands of the myocardium and increase the amount of time before irreversible damage occurs. This can be accomplished by reducing the workload of the left ventricle (which is the largest energy-consuming portion of the heartl. An /ABP is placed into the aorta and used as described above, resulting in a decreased afterload on the heart and incn:ased perfusion of the coronary arteries and peripheral organs.
Art alternative way to reduce myocardial oxygen demand _ø

is to reduce the volume of blood the left ventricle must pump. This can be atxompfished by reducing the load on the left verttride, such as in a cardiopulmonary bypass or use of an LUAD. Unloading the left veMride decreases the energy requir~nts of the myocardium and increases the amorfit of tine betore irreversible damage octxns. This provides an opportunity to more effectively remove or decrease the blockage and safYage myocardial function. To be sub each of these techniques must be implemsrrted within a short amount of tune after the onset of a myocardial infarction. The d~sadvamage, however, is that each of these techniques can only be performed in an emergency room or hospital setterg. Unless the patieltt is already in the hospital when the myocardial infarction occurs, there is usually some level of irreversrbk damage and sr>bsequem loss of myocardial functxxr.
li would he advantageous, therefore, to employ a heart assist system that avoids major invasive surgery and also avoids the use of peripheral equipment that severely restricts a patient's movement.
It would also be advantageous to have such a heart IO assist system that can be employed in a non-hospital setting for ease of treating acute heart problems under emergency conditions.
Surrmarv Of The tnvenfxxr An object of an aspect of the present invention is to aadress the aspect or t;tit- chat results from attereu pump function and abnormal circulatory dynamics wtale ovenrortwrg the lirtritations of prior art heart assat systems. Without functioning as a bypass to one a more of a patient's orgaru, the presem invention comprises sn extracardiac pumping system for supplementing the drculation of blood through the patient without any component thereof being connected to the patient's heart or primary vessels. Thus, 'tt is extracanliac in nature. Hrrrth the ability to be applied within a mioanally invasive procedure, the present invention sigrniffi~ntfy improves the condition of the patiem suffeimg from CHF, resulting in the patient feeling much better, even where CHF continues. By supplertrenting the pumping action of the heart, in lieu of replaang i4 the present system takes advantage of the pulsatile action of the heart, despite its weakened condition, to effectively detivar blood to body organs that benefit from pulsatie delivery of oxygenated blood. As a result, the present system is capable of being operated in a continuous flow fashion or, 'rf desired, in a pulsatae flow fashion.
An anallary but important benefit of the present inve~rtion is the abaity to apply the present invention in such a way as to also reduce the pumping toad on the heart, thereby potentially permitting the heart to mover during use. With the present invertt'ron, no bulky pump, valves or oxygenator are required, and no thoracic invasion with major cardiac surgery is reqtirced. Indeed, a significant advantage of the present invention is its s'vnpficity wh~e achieving extraordinary results in improving the condition of a gallant suffering from CHF.
The extracardiac system of the present invention preferably comprises, in one example, a rotary pump configured to pump blood thror>Dh the patient at subcardac rates; i. e., at a flow rate significantly below that of the pai'nmt's heart. Other types of pumps or flow generating mechardsms may be effective as weA. Pumping the blood tends to rev'ttafae the bbd to a certain extent by imparting kinetic~and potential energy to the blood disdtarged from the ptsnp.
Importantly, the preferred pump for the present inventimr pumping system is one that requires a relatively tow amount of energy input, when compared to prior art ptarrps designed to pump at cardiac rats. The prang may be implanted or not, depending upon the capabt'ity, practicality, or treed of the pat'rem to be ambulatory.
The present system also czurtprises an inflow conduit fluitgy coupled to the pump, to d'rcect blood to the pump frtKrr a first peripheral blood vessel, and an outflow conduit fluidly coupled to the pump, to direct blood from the pump to a second pe~tpheral blood vessel. The connection of the inflow and outflow conduits to the respective blood vessels is performed subcutaneously; not so deep as to involve major invasive surgery. In other words, minimally subdermal. This pem><ts application of the connect'roru in a min'snapy-invasive procedure. Preferably, the connections to the blood vessels are just below the skin or just below the first layer of musde, depending upon the blood vessels at issue or the location of the connection, although slightly deeper penetrations may be necessary for some patients or for same applications.
In an alternative embod'unem, the present system is applied at a single cannulated site using, for example, a multi-lumen catheter having at least one lumen as an inflow lumen and a second lumen as an outlet lumen. The mufti-Iwnen catheter has an inflow S port in fluid communicating with the inflow lumen. With this embodiment, blood is drawn into the inflow pert of the first lumen from a first peripheral blood vessel site, preferably the blood vessel into which the molts-Irmen catheter is inserted. The output of the pump directs blood through a second (outlet) port at the distal end of the second lumen that is preferably located in a second peripheral vessel site. This method accomplishes the same beneficial results achieved in the previously descnbed ~nbodunents, but requires only a single cannulated site, rather than two such s'rces. It should be appreciated that the molts-hrrrrar catheter could be used in a manner where the outflow of the cannula is to the first peripheral site, wtule the inflow is drawn from the second peripheral vessel. Further still, it should be appreaated that the inflow could be positioned to draw blood from a peripheral vessel at the site of entry into the patient while the outflow could be positioned in the aorta, proxunate an arterial branch.
In one embodiment of the extracardiac system, the pump is a continuous flow pump, a pulsatile pump, andlor a pump that is configured to generate flow in both a continuous and pulsatile fomrat. The pump may be implantable and is used to connect two peripheral arteries, such as the femoral artery at the inflow and the left axillary artery at the outflow, although other peripheral blood vessels are contemplated, including other arteries and)or veins, as well as any singular and)or cumulative combination thereof. An alternative embodiment employs both a continuous flow and a pulsatile flow pump connected in parallel or in series and operating simultaneously or in an alternating fashion. Yet another ahernative embodiment employs a rotary pump that is controllable in a synchronous copulsating or counterpulsating fash'ron, or in some out-of-phase intermediate thereof. In one application, it is contemplated that the present invention be applied such that the heart experiences a reduced pressure at the aortic root during systole (afterload) and)or a reduced left ventricular end diastolic pressure 4pre-load), thus reducing the hemodynamic burden or workload on the heart and, thus, permitting the heart to recover.
It is contemplated that, where the entire system of the present invention is implanted, that it be implanted subcutaneously without the need for mapr invasive surgery and, preferably, extrathoracically.
For example, the pump may be implanted in the groin area, with the inflow conduit attached to the femoral or iliac artery proximate thereto and the outflow conduit attached to the axillary artery proximate the shoulder. It is contemplated that the outflow conduit be applied by tunneling it under the skin from the pump to the axitlary artery. Where onplarrted, the pump is preferably powered by an implantable power source, such as for example a battery, that may be regenerated externally by an RF induction system or be replaced periodically, andlor a self-generating power source that, for example, draws energy from the human body f e. g., musdes, chemicals, heats.
The present invention also comprises a method for supplementing the drculation of blood in the patient and potentially reducing the workload on the heart of a patient without connecting any component to the patient's heart. The inventive method comprises the steps of implanting a pump configured to generate blood flow at volumetric rates that are on average subcardiac, wherein the pump has an inflow and outflow conduit attached thereto;
connecting a distal end of the inflow conduit to a first peripheral blood vessel with a minimally-invasive surgical procedure to pemut the flow of blood to the pump from the first peripheral blood vessel of the patient; implanting the inflow conduit subcutaneously; connecting a distal end of the outflow conduit to a second peripheral blood vessel with a minimally-invasive surgical procedure to pemut the flow of blood away from the pump to the second peripheral blood vessel of the patient; and operating said pump to perfuse blood through the patient's circulatory system. Where the second peripheral blood vessel is the axillary artery, the step of connecting the distal end of the outflow conduit is performed in such a manner that a sufficient flaw of blood is din;cted toward the hand to avoid limb ischemia while ensuring that sufficient flow is directed toward the aorta without damaging the endothelial Lining of the second peripheral blood vessel. The same concerns for avoiding limb ischemia and damage to the endothelial lining would apply, however, regardless of the selection of second peripheral blood vessel.
In one specific application, the pump is capable of synchronous control wherein the step of operating the pump includes the steps of beginning discharge of blood out of the pump during isovohanic contraction and discontinuing discharge of blood when the aortic valve closes following systole. Depending upon the patient and the specific arrangement of the present system, this speci5c method results in reduced aherload and)or preload on the heart while also supplementing circulation. For example, in one embodunent, the fast and second blood vessels are the femoral and axillary arteries, respectively.
In an alternative method of applying the present invention, the pump is not implanted and the inflow and outflow condu'rcs are connected to the first and second blood vessels percutaneously, using a readily-removable connector, such as a cannula, to connect the distal ends of each condu-rt to the bMod vessels.
An important advantage of the present invention is that it utTizes the benefrts of an IABP, without the requirement of extracorporeal equipment or the need to have a balloon or simrlar implement partially obstructing a blood vessel. In add>tion to the benefrts of an IABP, it also offers the benefit of reduang the preload on the heart. The present invention thus offers simpGc'rty and long-term use.
Another important advantage of the present invention is its potential to enhance mixing of systemic arterial blood, particularly in the aorta, and thereby deliver blood with a higher oxygen-canying capacity to organs supplied by arterial side branches off of the aorta. This overcomes the problem of blood streaming in the descending aorta that may sometimes occur in patients suffering from low cardiac output or other ailments resulting in low blood flow. The lack of mixing of the blood within the descending aorta that may result from blood streaming could lead to a higher concentration of red blood cells and nutrients in the central region of the aorta and a decreasing concentration of red blood cells loser to the aortic wall.
This could resuh in lower hematocrit blood flowing into branch arteries from the aorta.. Where it is desired to address the potential problem of blood streaming, a method of utilizing the present invention may include taking steps to assess certain parameters of the patient and then to determine the minimum output of the pump that ensures turbulent flow in the aorta, thereby enhancing blood mixing.
Brief Description Of The Drawings These and other features and advantages of the invention will now he described with reference to the drawings, which are intended to illustrate and not to limit the irnerttiort.
Figure 1 is a schematic view of a cardiac assist device, known as a left ventricular assist device, showing a bypass from the apex of the left ventricle to the aortic arch;
Figure 2 is a schematic view of a first embodiment of the present invemion, shown appfied to a patient's circulatory syst~rr.
Figure 3 is a schematic view of a second embodiment of the present invention, shown applied to a patient's circulatory system.
Figure 4 is a schematic view of a variation of the first embodiment of Figure 2 shown implanted into a pafient;
Figure 5 is a schematic view of a third embodunent of the present invention, shown applied to a patient's circulatory system.
Figure 6 is a schematic view of a fourth embodiment of the present invention, shown applied to a patient's circulatory system.
Figure 7 is a schematic view of an inflow L-shaped connector, shown inserted within a blood vessel.

Figure 8 is a schematic view of a fifth embodunent of the presets invention employing a mufti-lumen catheter for single site application to a patient Figure 9 is a schematic view of a sath embodunent of the present invemion showing a reservoir and a portable housing for carrying a portion of the invention directly on the patient.
()etailed Oescriotion Of The Preferred Embodiments Turning now to the drawings provided herein, a more detaled description of the embodiments of the present invention is provided below. It should be noted, however, that while some embodiments have all of the advantages identified herein, other embodiments may only realae some but not al) of the advantages.
The present invention provides a heart assist system that is extracardiac in nature. In other words, the present invention supplements blood perfusion, without the need to interface directly with the heart and aorta. Thus, no major invasive surgery is necessary to use the present invention. The present invention also lessens the hemodynamic burden or workload on the heart by reducing the pressure at the aortic root during systole (afterload~ andJor reducing left ventricular end diastolic pressure and volume (preload).
With reference to Fgure 2, a first embodiment of the present invention 10 is shown applied to a patient 12 having an aTing heart 14 and an aorta 16, from which peripheral brachiocephalic blood vessels extend, including the right subclavian 18, the rigftt carotid 20, the left carotid 22, and the left axillary 24. Extending from the descending aorta is another set of peripheral blood vessels, the left and right temoral arteries 26, 28.
The first embodiment 10 comprises a pump 3Z, having an inlet 34 and an outlet 36 for connection of flexible conduits thereto. The pump 32 is preferably a rotary pump, either an axial type or a centrifugal type, although other types of pumps may be used, whether commercially-available or customized. In either case, the pump should be sufficiently small to be implanted suhcutaneously and preferably extrathoracically, for example in the groin area of the patient, without the need far major invasive surgery. Because the present invention is an extracardiac system, no valves are necessary. Any inadvertent backflow through the pump and/or through the inflow candu'rt would not harm the patient.
Regardless of the style or nature chosen, the pump 32 of the present invention is sized to generate blood flow at subcardiac volumetric rates, less than about 50% of the flow rate of an average healthy heart, ahhough flow rates above that may be effective.
Thus, the pump 32 of the present invention is sized and configured to discharge blood at volumetric flow rates anywhere in the range of 0.1 to 3 titers per minute, depending upon the application desired and(or the degree of need for heart assist. For example, for a patient experiencing advanced congestive heart tailure, 'rt may be preferable to employ a purrs that has an average subcardiac rate of 2 5 to 3 liters per minute. In other patients, particularly those with minimal levels of heart failure, it may be preferable to employ a pump that has an average subcardiac rate of 0. 5 filers per minute or less. In yet other patients it may be preferable to employ a pump that is a pressure wave generator that uses pressure to augment the flow of blood generated by the heart.
In one embodunent, the purr~r selected is a continuous flow pump so that blood perfusion through the circulation system is continuous. In an alternative embodiment, the pump selected has the capability of synchronous actuation; i, e., it may be actuated in a pulsatile mode, either in copulsating or counterpulsating fashion.
For copulsatmg action, it is contemplated that the pump 32 would be actuated to discharge blood generally during systole, beginning actuation, for example, during isovoirunic contraction before the aortic valve opens ar as the aortic valve opens. The pump would be static while the aortic valve is closed following systole, ceasing actuation, for example, when the aortic valve closes.
_g_ For counterpulsating actuation, it is contemplated that the pump 32 would be actuated generally during diastole, ceasing actuation, for example, before or during isovolumic contraction. Such an application would permit andlor enhance coronary blood perfusion. In this application, it is contemplated that the pump would be static during the balance of systole after the aortic vahre is opened, to lessen the burden against which the heart must purr. The aortic valve being open encompasses the periods of opening and closing, wherein blood is flowing therethmugh.
It should be recognized that the designations copulsating and counterpulsating are general identifiers and are not limited to specific points in the patient's heart cycle when the pump begins and discontinues actuation. Rather, they are intended to generally refer to pump actuation in which the pump is actuating, at least in part, during systole and diastole, respectively. For example, 'rt is contemplated that the pump might be activated to be out of phase from true copulsating or courtterpulsating actuation descrbed herein, and still be synchronous, depending upon the specific needs of the patient or the desired outcome. One might shift actuation of the pump to begin prior to or after isovolumic contraction or to begin before or after isovolumic expansion.
Furthermore, the pulsatle pump may be actuated to pulsate asynchronously with the patient's heart. Typically, where the patient's heart is beating irregularly, there may be a desire to pulsate the pump asynchronously so that the perfusion of blood by the extracardiac pumping system is more regular and, thus, more effective at oxygenating the organs. Where the patient's heart beats regularly, but weakly, synchronous pulsation of the extracardiac pump may be preferred.
The pump 32 is driven by a motor 40 andlor other type of drive means and is controlled pnferably by a programmable controller 42 that is capable of actuating the pump in pulsatle fashion, where desired, and also of controlling the speed or output of the pump. For synchronous control, the patient's heart would preferably be monitored with an EKG in which feedback would be provided the controller 42 The controner 42 is preferably programmed by the use of external means. This may be accomplished, for example, using RF telemetry circuits of the type commonly used within implantable pacemakers and defibrillators. The controller may also be autoregulating to permit automatic regulation of the speed, andlor regulation of the synchronous or asynchronous pulsation of the pump, based upon feedback from ambient sensors monitoring parameters, such as pressure or the patient's EKG. It is also contemplated that a reverse-direction pump be utilized, if desired, in which the controller is capable of reversing the direction of either the drive means or the impellers of the pump. Such a pump might be used where it is desirable to have the option of reversing the direction of arculation between two peripheral blood vessels.
Power to the motor 40 and controller 42 may be provided by a power source 44, such as a battery, that is preferably rechargeable by an external induction source (not shownh such as an RF
induction col that may be electromagnetically coupled to the battery to induce a charge therein. Alternative power sources are also possible, including a device that draws energy directly from the patient's body; e. g., the patient's muscles, chemicals or heat. The purl can be temporarily stopped during recharging with no appreciable Gfe threatening effect, because the system only supplements the heart, rather than substituting for the heart.
While the controller 42 and power source 44 are preferably pre-assembled to the pump 32 and implanted therewith, it is also contemplated that the pump 32 and motor 40 be implanted at one location and the controller 42 and power source 44 be implanted in a separate location. In one ahemative arrangement, the pump 32 may be driven externally through a percutaneous drive line. In another alternative, the pump, motor and controller may be implanted and powered by an extracorporeal power source. In the latter case, the power source could be attached to the side of the patient to pemut fully ambulatory movement.
The inlet 34 of the pump 32 is preferably connected to a flexible inflow conduit 50 and a flexible outflow conduit 52 to direct blood flow from one peripheral blood vessel to another. The inflow and outflow conduits 50, 52 may, for example. be formed from Dacron, Hemashield or Gortex materials, although other synthetic materials may be suitable. The inflow and outflow conduits 50, _9_ 52 may also comprise biologic materials or pseudobiological Ihybridl materials (e. g., biologic tissue supported on a synthetic scaffold).
The inflow and outflow conduits are preferably configured to rr~emtize kinks so blood flow is not meamingfugy interrupted by normal movements of the patibnt or compressed easily from external forces. !n some cases, the inflow andlor outflow conduits may come commercially already attached to the pump. Where it is desired to implant the pump 32 and the conduits 50, 52, -rt is preferable that the inner diameter of the conduits be less than 25 mm, ahhough diameters slightly larger may be effective.
In one preferred application of the present invention, the first embodiment is applied in an arterial-arterial fashion; for example, as a femoral-axllary connection, as is shown in Fgure 2 It should be appreciated by one of ordinary skill in the art that an axillary-femoral connection would also be effective using the embod~rnents descn'bed herein. Indeed, it should be recognized by one of ordinary sk81 in the art that the present wention might be applied to arty of the peripheral blood vessels in the patient.
The inflow conduit 5D has a first proximal gird 56 that connects with the inlet 34 of the pump 32 and a second distal end 58 that connects with a first peripheral blood vessel, which is preferably the left femoral artery 26 of the patient 12, although the right femoral artery or any other peripheral artery may be acceptable. In one application, the connection between the inflow conduit 5D and the first blood vessel is via an end-to-side anastomosis, although a side-to-side anastomosis connection might be used mid-stream of the conduit where the inflow conduit were connected at its second end to an additional blood vessel or at another location on the same blood vessel Ine'tther shownl.
Similarly, the outflow conduit 52 has a first proximal end 62 that connects to the outlet 36 of the pump 32 and a second distal end 64 that connects with a second peripheral blood vessel, preferably the left axillary artery 24 of the patient 12, ahhough the right axillary artery, or any other peripheral artery, would be acceptable. In one application, the connection between the outflow condrbt 52 and the second blood vessel is via an end-to-side anastomosis, although a side-to-side anastomosis connection might be used mid-stream of the condo-rt where the outflow eondu-rt were connected at its second end to yet another blood vessel (not shown) or at another location on the same blood vessel. Preferably, the outflow conduit is attached to the second blood vessel at an angle that results in the predominant flow of blood out of the pump proximally toward the aorta and heart, such as is shown in I figure 2, while still maintaining sufficient flow distany toward the hand to prev~t I-anb isdrerrria.
It is preferred that application of the present invention to the peripheral blood vessels be accomplished subcutaneousiy; i. e., at a shallow depth just below the skin or first muscle layer so as to avoid major invasive surgery. It is also preferred that the present invention be applied extrathoracically to avoid the need to invade the pati~t's chest cavity. Where desired, the entire extracardiac system of the present invention 10 may be implanted within the patient 12. In that case, the pump 32 may be implanted, for example, into the groin area, with the inflow conduit 50 connected subcutaneousfy to, for example, the femoral artery Z6 proximate the pump 3Z
The outflow conduit would be tunneled subrzrtaneously through to, for example, the left axillary artery 24. In art ahemative arrangement, the pump 32 and associated drive and controller could be temporarihr fastened to the exterior skin of the patient, with the inflow and outflow condo-it 50, 52 connected percutaneously. In either case, the patient may be ambr>aatory without restriction of tethered fines.
ft is contemplated that, where an anastomosis connection is not desired, a special connector may be used to connect the conduits 5D, 52 to the peripheral blood vessels. With reference to Fgure 3, a second embodiment of the present invention is shown, wherein the inflow conduit 50 and outflow conduit 52 are connected to the peripheral blood vessels via first and second connectors 68, 70 each comprising three~pening frttings. fn the preferred embodiment, the connectors 68, 70 comprise art infra-vascular, generally-tee-shaped fining 72 having a proximal end 74, a distal end 76, and an angled divergence 78 permitting connection to the inflow and outflow conduits 50, 52 and the blood vessels. The proximal and distal ends 74, 76 of the fittings 72 pem~it connection to the blood vessel into which the fitting is positioned. The angle of diiergence 78 of the fittings 72 may be 90 degrees or less in either direction from the axis of flow through the blood vessel, as optimally selected to generate the needed flow distally toward the hand to prevent limb ischemia, and to insure sufficient flow and pressure toward the aorta to provide the circulatory assistance and workload reduction needed while minimizing or avoiding endothelial damage to the vessel. In another embodiment, the connectors 68, 70 are sleeves Inot shown) that surround and attach to the outside of the peripheral blood vessel where, within the interior of the sleeve, a part to the blood vessel is provided to permit blood flaw from the conduits 50. 52 when they are connected to the connectors 68, 70, respectively.
Other types of connectors having other configurations are contemplated that may avoid the need for an anastomosis connection or that permit connection of the conduits to the blood vessels. For example. it is contemplated that an L-shaped connector be used if it is desired to withdraw blood more predominantly from one direction of a peripheral vessel or to direct blood more predominantly into a peripheral vessel. Referring to Figure 7, an inflow conduit 50 is fluidly connected to a peripheral vessel, for example, the left femoral artery 26, using an L-shaped connector 310. The connector 310 has an inlet port 312 at a proximal end and an outlet port 314 through which blood flows iota the inflow conduit 50. The connector 310 also has an arrangement of holes 316 within a wall positioned at a distal end apposite the inlet port 312 so that some of the flow drawn irrto the connector 310 is diverted through the holes 312, particularly downstream of the connector, as in this application. A single hole in the wall could also be effective, depending upon size and placement. The connector may be a deformable L-shaped catheter percutaneously applied to the blood vessel or, in an alternative embodimem, he cormected directly to the walls of the blood vessel for more long term application. By directing some blood flaw downstream of the connector during withdrawal of blood from the vessel, ischemic damage downstream from the connector may be avoided. Such ischemic damage might otherwise occur if the majority of the blood flowing into the irrflow connector were diverted ftom the blood vessel into the inflow conduit. !t is also contemplated that a connection to the blood vessels might be made via a cannula, wherein the cannula is implanted, along with the inflow and outflow conduits.
The advantage of disaete connectors is their potential application to patients with chronic CHF. A connector eliminates a need for an anastomosis connection between the conduits of the present invention system and the peripheral blood vessels where it is desired to remove andfor replace the system more than one time. The connectors could be appfu:d to the first and second blood vessels semi-permanently, with an end cap appfied to the divergence for later quick-connection of the present invention system to the patient.
In this regard, a patient might experience the benefit of the present invention periodically, without having to reconnect and redisconneci the conduits from the blood vessels via an anastomosis procedure each tune.
Each time it is desired to implement the present invention, the end caps would be removed and the conduit attached to the connectors quickly.
In the preferred embod~nt of the connector 70, the divergence 78 is oriented at an acute angle signficantty less than 90°
from the axis of the fining 7Z, as shown in Figure 3, so that a majority of the blood flowing through the outflow conduit 52 into the blood vessel (e. g., left axillary 24) flows in a direction proximally toward the heart 14, rather than in the distal direction. In an alternative embodiment, the proximal end 74 of the fitting 72 may have a diart~ter larger than the diameter of the distal end 76, without need of having an angled divergence, to achieve the same result.
VYith or without a connector, with blood flow erected proximally toward the aorta, the result may be concurent flow down the descending aorta, which will result in the reduction of pressure at the aortic root. Thus, the present invention may be applied so to reduce the afterload on the patient's heart, permitting at least partial 'rf not complete CHF recovery, while supplementing blood circulation. Concurrent flow depends upon the phase of operation of the pulsatile pump and the choice of second b~od vessel to which the outflow conduit is connected.

Whle the present invention may be applied to create an arterial-arterial flow path, given the nature of the present invention, i.
e., supplementation of circulation to meet organ demand, a venous~arterial flow path may also be used. For example, with reference to Figure 4, one embodiment of the present invention 10 may be applied to the patient 12 such that the inflow conduit 50 is connected to a peripheral vein, such as the left femoral vein 80. In this arrangement, the outflow conduit 5D may be connected to one of the peripheral arteries, such as the left axillary 24. Arterial-venous arrangements are contemplated as wail. In those venous-arterial cases when: the inflow is connected to a vein and the outflow is connected to an artery, the pump 32 should be sized to permit flow sufficiently small so that oxygen-deficient blood does not rise to unacceptable levels in the arteries. It stbuld be appreciated that the connections to the peripheral veins could be by one or mare methods described above for connecting to a peripheral artery. It should also be appreciated that the present invention could be applied as a venous-venous flow path, wherein the inflow and outflow are connected to separate peripheral veins. In addition, an alternative embodiment comprises two d'ucrete pumps and conduit arrangements, one being applied as a venous-venous flow path, and the other as an arterial-arterial flow path. When venous blood is mixed with arterial blood either at the inlet of the pump or the outlet of the pump the ratio of venous blood to arterial blood should be controlled to maintain an arterial saturation of a minirtuxn of 8D% at the pump inlet or outlet. Arterial saturation can be measured and/or monitored by pulse oximetry, laser doppler, colorQnetry or other methods used to monitor blood oxygen saturation. The venous blood flow into the system can then be controlled by regulating the amount of blood allowed to pass through th4 conduit from the venous~side conneMion.
A partial external application of the present invention is contemplated where a patient's heart failure is acute: i. e., is not expected to last long, or in the earlier stages of heart failure (where the patient is in New York Heart Association Classification (NYHAC) functional classes II or Ill). With reference to Figure 5, a third embodiment of the present invention 110 is applied percutaneously to a patient 112 to connect two peripheral blood vessels wherein a pump 132 and its associated driving means and controls are employed extracorporeally. The pump 132 has an inflow conduit 150 and an outflow conduit 152 associated therewith for connection to two peripheral blood vessels. The inflow conduit 150 has a first end 156 and second end 158 wherein the second end is connected to a first peripheral blood vessel le. g., femoral artery 126) by way of a cannula 180. The cannula 180 has a first end 182 sealably connected to the second end 158 of the inflow conduit 150. The cannula 180 also has a second end 184 that is inserted through a surgical opening 186 or an introducer sheath (not shown) and into the blood vessel source (e. g" femoral artery 126).
Similarly, the outflow conduit 152 has a first end 162 and second end 164 wherein the second end is connected to a second peripheral blood vessel (e. g., left axillary artery 124) by way of a cannula 180. Like the inflow cannula, the outflow cannula 18D has a frrst end 182 sealably connected to the second end 164 of the outflow conduit 152. The outfbw cannula 180 also has a second end 184 that is inserted through surgical opening 190 or an introducer sheath (not shown) and irrto the second blood vessel (e. g., left 3 0 axillary artery 124). By use of a percutaneous application, tire present invention may be applied temporarily without the need to implam any aspect thereof or to make anastomosis connections to the blood vessels.
It is contemplated that a means for miriunizing the loss of thermal energy in the patient's blood be provided where the present inventive system is applied extracorporeally. Such means for minimaing the loss of thermal energy may comprise, for example, a heated bath through which the inflow and outflow conduits pass or, alternafrvely, thermal elements secured to the exterior of the 3 $ inflow and outflow conduits. Referring to Figure 9, one embodiment comprises an insulating wrap 402 surrounding the outflow conduit 152 having one or more thermal elements passing therethrough. The elements may be powered, for exart~le, by a battery (not shown).
One advantage of thermal elements is that the patient may be ambulatory, if desired. Other means that are known by persons of ordinary skill in the art for ensuring that the temperature of the patient's blood remains at acceptable levels while travelling extracorporeaily are also contemplated.
An alternative variation of the third embodiment may be used where it is desired to treat a patient periodically, but for short periods of time each occasion and without the use of special connectors. With this variation, it is contemplated that the second ends of the inflow and outflow conduits be more permanently connected to the associated blood vessels via, for example, an anastomosis connection, wherein a portion of each conduit proximate to the blood vessel connection is implanted percutaneously with a removable cap enclosing the externally-exposed first end for an intervening end thereof) of the conduit external to the patient. When 'rt is desired to provide a circulatory flow path to supplement blood flow, the removable cap on each exposed percutaneously-positioned conduit could be removed and the pump (or the pump with a length of inflow andlor outflow conduit attached theretol inserted between the exposed percutaneous conduits. In this regard, a patient may experience the benefrt of the presets invention periodically, without having to reconnect and redisconnect the conduits from the blood vessels each time.
Another embodmrent of the present invention includes a plurality of inflow andlor outflow conduits. For example, with reference to i=egure 6, a fourth embodiment of the present invention 210 includes a pump 232 in fluid communication with a plurality of inflow conduits 250A, 2508 and a plurality of outflow conduits 252A, 2528. Each pair of conduits converges at a generally Y-shaped convergence 296 that converges the flow at the inflow end and diverges the flow at the outflow end. Each conduit may be connected to a separate peripheral blood vessel. although it is possible to have two connections to the same blood vessel at remote locations. to one arrangement, all tour conduits are connected to peripheral arteries. Alternatively, one or more of the conduits could be connected to veins. In the application shown in Figure 6, inflow conduit 25DA is connected to left femoral artery 226 while inflow conduit 25DB is connected to left femoral vein 278. Outflow conduit 252A is connected to left axillary artery 224 while outflow conduit 2528 is connected to left carotid artery 222. It should be noted that the connections of any or all of the conduits to the blood vessels may be via an anastomosis connection or via a special connector, as described above. In addition, the embodiment of Figure 6 may be applied to any combination of peripheral blood vessels that would best suit the patient's condition. For example, it may be desired to have one inflow conduit and two outflow conduits or vice versa. ft should be noted that more than two conduits may be used on the inflow or outflow side, where the number of inflow conduits is not necessarily equal to the number of outflow conduits.
If desired, the present inventive system may further comprise a reservar that is either contakred within or in fluid communication with the inflow conduit. This reservoir is preferably made of materials that are nonthrortrbogenic. Referrir>g to Figure 9, a reservoir 420 is positioned fluidly in late with the inflow conduit 150. Tha reservoir 420 serves to sustain adequate blood in the system when the pump demand exceeds momentarily the volume of blood available in the peripheral blood vessel in which the inflow conduit resides until the pump output can be adjusted. The reservoir reduces the risk of excessive drainage of blood from the peripheral blood vessel, which may occur when cardiac output falls farther than the already diminished baseline level of cardiac output, or when there is systemic vasodilation, as can occur, for example, with septic shock.
It is contemplated that the reservoir would be primed with an acceptable solufron, such as saline, when the present system is first applied to the patient.
In an alternative embodiment, the present system comprises a multi-lumen catheter whereby the system may be applied by insertion at a single cannulated site while the inflow and outflow conduits still fluidly communicate with peripheral vessels. Referring to Figure 8, a multi-lumen catheter 510 could be inserted, for example, into the left femoral artery 26 and guided superiorly through the descending aorta to one of numerous locations. The blood could discharge, for example, directly into the descending aorta proximate an arterial branch, such as the left subclavian artery or, as shown in Figure 2 by way of example, directly into the peripheral mesenteric artery 30. Preferably, the multi-lumen catheter 510 has an inflow port 512 that may be positioned within the left femoral artery 26 when the catheter 510 is fully inserted so that blood drawn from the left femoral artery is directed through the inflow port 512 into a first lumen 514 in the catheter. This blood is then purt>ped through a second)umen 516 in the catheter and out through an outflow port 520 at the distal end of the catheter 510. The outflow port 520 may be situated within, for example, the mesenteric artery 30 such that blood flow results from the left femoral artery 26 to the mesenteric artery 30. Preferably, where there is a desire far the patient to be ambulatory, the muhi-lumen catheter 510 should preferably be made of material sufficiently flexible and resilient to permit the patient to be comfortably move about while the catheter is indwelFmg irt the patient's blood vessels without causing any vascular trauma As explained above for several embodiments, one of the advantages of the present heart assist system is that it permits the patient to be arnbufatory. If desired, the system may be designed portably so that it may be carried directly on the patient. Referring to Fgure 9, this may be accomplished through the use of a portable case 610 with a belt strap 612 to house the pump, power supply andlor the controller, along with certain portions of the inflow andlor outfbw conduits, if necessary. It may also be accompf~shed with a shoulder strap or other techniques, such as a backpack or a fanny pack, that permit effective portability. As shown in Fgure 9, blood is drawn through the inflow conduit 150 into a pump contained within the portable case 610, where it is discharged into the outflow 1 S conduit 152 back into the patient.

Claims (37)

1. An extracardiac pumping system for treating a patient without any component thereof being connected to the patient's heart, the extracardiac system comprising:
a pump configured to pump blood through the patient at subcardiac volumetric rates, said pump having an average flow rate that, during normal operation thereof, is substantially below that of the patient's heart when healthy;
an inflow conduit comprising flexible tubing having an inner diameter that is less than 25 millimeters fluidly coupled to the pump to direct blood to the pump from a first non-primary blood vessel; and, an outflow conduit comprising flexible tubing having an inner diameter that is less than 25 millimeters fluidly coupled to the pump and configured to direct blood from the pump to a renal artery;
whereby connection of the first ends of the inflow and outflow conduits to the blood vessel may be made subcutaneously to permit application of the connections in a minimally-invasive procedure.

2. The pumping system of Claim 1, wherein the inflow conduit is configured to couple with a femoral artery.

3. The pumping system of Claim 1, wherein the inflow conduit defines a first lumen of a multilumen catheter and the outflow conduit defines a second lumen of the multilumen catheter.

4. The pumping system of Claim 1, wherein the outflow conduit comprises a cannula configured to be inserted into the vasculature and advanced to a location proximate the renal artery.

5. The pumping system of Claim 1, wherein the outflow conduit comprises a cannula configured to be inserted into the vasculature and advanced to a location within the renal artery.

6. The pumping system of Claim 1, further comprising a cannula coupled with the outflow conduit, the cannula being configured to be inserted into the vasculature and advanced to a location proximate the renal artery.

7. The pumping system of Claim 1, further comprising a cannula coupled with the outflow conduit, the cannula being configured to be inserted into the vasculature and advanced to a location within the renal artery.

8. The pumping system of Claim 1, wherein the inflow conduit comprises a cannula configured to be inserted into a first femoral artery.

9. The pumping system of Claim 8, wherein the outflow conduit comprises a cannula configured to be inserted into the first femoral artery and advanced to a location proximate the renal artery.

10. The pumping system of Claim 8, wherein the outflow conduit comprises a cannula configured to be inserted into the first femoral artery and advanced to a location within the renal artery.

11. The pumping system of Claim 8, further comprising a cannula coupled with the outflow conduit, the cannula being configured to be inserted into the first femoral artery and advanced to a location proximate the renal artery.

12. The pumping system of Claim 8, further comprising a cannula coupled with the outflow conduit, the cannula being configured to be inserted into the first femoral artery and advanced to a location within the renal artery.

13. The pumping system of Claim 8, wherein the outflow conduit comprises a cannula configured to be inserted into a second femoral artery and advanced to a location proximate the renal artery.

14. The pumping system of Claim 8, wherein the outflow conduit comprises a cannula configured to be inserted into a second femoral artery and advanced to a location within the renal artery.

15. The pumping system of Claim 8, further comprising a cannula coupled with the outflow conduit, the cannula being configured to be inserted into a second femoral artery and advanced to a location proximate the renal artery.

16. The pumping system of Claim 8, further comprising a cannula coupled with the outflow conduit, the cannula being configured to be inserted into a second femoral artery and advanced to a location within the renal artery.

17. A method for treating a patient without connecting any component to the patient's heart, the method comprising the steps of:
connecting a distal end of an inflow conduit of a pump to a first artery that is not the aorta or pulmonary artery using a minimally invasive surgical procedure to permit the flow of blood to the pump from the first artery, said pump configured to pump blood at volumetric rates that are on average subcardiac;
inserting a distal end of an outflow conduit of the pump into the vasculature using a minimally invasive surgical procedure to permit the flow of blood away from the pump to the vasculature;
advancing the distal end of the outflow conduit within the vasculature to a location adjacent a renal artery; and operating said pump to perfuse blood through the patient's circulatory system at volumetric rates that are on average subcardiac.

18. The method of Claim 17, further comprising advancing the distal end of the outflow conduit within the vasculature to a location within a renal artery; and

19. A method for improving perfusion of organs through a branch artery without connecting any component to the patient's heart, the method comprising the steps of:
connecting a distal end of an inflow conduit of a pump to a first artery that is not the aorta or pulmonary artery using a minimally invasive surgical procedure to permit the flow of blood to the pump from the first artery, said pump configured to pump blood at volumetric rates that are on average subcardiac;
inserting a distal end of an outflow conduit of the pump into the vasculature using a minimally invasive surgical procedure to permit the flow of blood away from the pump to the vasculature;

advancing the distal end of the outflow conduit within the vasculature to a location adjacent a branch artery; and operating said pump to perfuse blood through the patient's circulatory system at volumetric rates that are on average subcardiac.

20. The method of Claim 19, wherein the branch artery is a renal artery.

21. The method of Claim 20, wherein the step of connecting the distal end of the inflow conduit comprises connecting the distal end of the inflow conduit to a first femoral artery.

22. The method of Claim 21, wherein the step of inserting the distal end of the outflow conduit into the vasculature further comprises inserting a cannula located at the distal end of the outflow conduit into the vasculature to a location proximate the renal artery.

23. The method of Claim 21, wherein the step of inserting the distal end of the outflow conduit into the vasculature further comprises inserting a cannula located at the distal end of the outflow conduit into the vasculature to a location within the renal artery.

24. The method of Claim 21, wherein the step of inserting the distal end of the outflow conduit further comprises inserting the distal end of the outflow conduit into the first femoral artery.

25. The method of Claim 24, wherein the step of inserting the distal end of the outflow conduit into the vasculature further comprises inserting a cannula located at the distal end of the outflow conduit into the vasculature to a location proximate the renal artery.

26. The method of Claim 24, wherein the step of inserting the distal end of the outflow conduit into the vasculature further comprises inserting a cannula located at the distal end of the outflow conduit into the vasculature to a location within the renal artery.

27. The method of Claim 21, wherein the step of inserting the distal end of the outflow conduit further comprises inserting the distal end of the outflow conduit into a second femoral artery.

28. The method of Claim 27, wherein the step of inserting the distal end of the outflow conduit into the vasculature further comprises inserting a cannula located at the distal end of the outflow conduit into the vasculature to a location proximate the renal artery.

29. The method of Claim 27, wherein the step of inserting the distal end of the outflow conduit into the vasculature further comprises inserting a cannula located at the distal end of the outflow conduit into the vasculature to a location within the renal artery.

30. The method of Claim 19, wherein the branch artery is a celiac trunk.

31. The method of Claim 19, wherein the branch artery is a spinal artery.

32. The method of Claim 19, wherein the branch artery is a superior mesenteric artery.

33. The method of Claim 19, wherein the branch artery is an inferior mesenteric artery.

34. A method for treating a patient without connecting any component to the patient's heart, the method comprising the steps of:
inserting a distal end of a multilumen catheter into the vasculature of a patient at a non-primary vessel using a minimally invasive surgical procedure to permit the flow of blood between a pump and the vasculature, the multilumen catheter defining a first lumen and a second lumen, the first lumen fluidly coupling an inflow port and the pump, the second lumen fluidly coupling an outflow port and the pump;
advancing the multilumen catheter until the outflow port is located within the vasculature proximate a renal artery; and operating said pump to perfuse blood through the patient's circulatory system at volumetric rates that are on average subcardiac.

35. The method of Claim 34, wherein the multilumen catheter is inserted into a femoral artery.

36. The method of Claim 34, wherein the multilumen catheter is advanced until the outflow port of the multilumen catheter is located within a branch artery.

37. The method of Claim 36, wherein the multilumen catheter is advanced until the outflow port of the multilumen catheter is located within a renal artery.