Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/24—Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
  • A61F2/2478—Passive devices for improving the function of the heart muscle, i.e. devices for reshaping the external surface of the heart, e.g. bags, strips or bands
  • A61F2/2487—Devices within the heart chamber, e.g. splints
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/00234—Surgical instruments, devices or methods, e.g. tourniquets for minimally invasive surgery
  • A61B2017/00238—Type of minimally invasive operation
  • A61B2017/00243—Type of minimally invasive operation cardiac

Definitions

• This invention relates generally to surgical methods and apparatus for performing surgical ventricular repair.
• a specific embodiment of the invention relates to methods and apparatus for repairing a dilated left ventricle of a human heart.
• the function of a heart in an animal is primarily to deliver life-supporting oxygenated blood to tissue throughout the body. This function is accomplished in four stages, each relating to a particular chamber of the heart. Initially deoxygenated blood is received in the right auricle of the heart. This deoxygenated blood is pumped by the right ventricle of the heart to the lungs where the blood is oxygenated. The oxygenated blood is initially received in the left auricle of the heart and ultimately pumped by the left ventricle of the heart throughout the body. It can be seen that the left ventricular chamber of the heart is of particular importance in this process as it is relied upon to pump the oxygenated blood initially through an aortic valve into and ultimately throughout the entire vascular system.
• the left ventricle which is the primary pumping chamber, is somewhat elliptical, conical or apical in shape in that it is longer, long axis longest portion from aortic valve to apex, than it is wide, short axis widest portion from ventricle wall to septum, and descends from a base with a decreasing cross-sectional circumference, to a point or apex.
• the left ventricle is further defined by a lateral ventricle wall and a septum, which extends between the auricles and the ventricles.
• Two types of motion accomplish the pumping of the blood from the left ventricle.
• One of these motions is a simple squeezing motion, which occurs between the lateral wall and the septum.
• the squeezing motion occurs as a result of a thickening of the muscle fibers in the myocardium. This compresses the blood in the ventricle chamber and ejects it into the body.
• the thickening changes between diastole and systole. This is seen easily by echocardiogram, PET and MRI imaging and can be routinely measured.
• the other type of motion is a twisting or writhing motion, which begins at the apex and rises toward the base.
• the rising writhing motion occurs because the heart muscle fibers run in a circular or spiral direction around the heart. When these fibers constrict they cause the heart to twist initially at the small area of the apex, but progressively and ultimately to the wide area of the base.
• These squeezing and twisting motions are equally important, as they are each responsible for moving approximately one-half of the blood pumped.
• the contractility or stiffness of these fibers are major determinants in how well the ventricle pumps.
• the amount of blood pumped from the left ventricle divided by the amount of blood available to be pumped is referred to as the ejection fraction of the heart.
• a healthier heart has a higher ejection fraction.
• a normal heart for example may have a total volume of one hundred milliliters and an ejection fraction of sixty percent. Under these circumstances, 60 milliliters of blood are pumped with each beat of the heart. It is this volume in the normal heart of this example that is pumped with each beat to provide nutrients including oxygen to the muscles and other tissues of the body.
• Ischemic cardiomyopathy typically occurs as the rest of the heart dilates in an attempt to maintain the heart's output to the body.
• the affected myocardium dies losing its ability to contribute to the pumping action of the heart.
• the ischemic muscle is no longer capable of contracting so it cannot contribute to either squeezing or twisting motion required to pump blood.
• This non-contracting tissue is said to be akinetic.
• the akinetic tissue which is not capable of contracting, is in fact elastic so that blood pressure tends to develop a bulge or expansion of the chamber.
• This muscle tissue is not only akinetic, in that it does not contribute to the pumping function, but it is in fact dyskinetic, in that it detracts from the pumping function. This is particularly detrimental as the limited pumping action available, as the heart loses even more of its energy to pumping the bulge instead of the blood.
• the body seems to realize that with a reduced pumping capacity, the ejection fraction of the heart is automatically reduced. For example, the ejection fraction may drop from a normal sixty percent to perhaps twenty percent. Realizing that the body still requires the same volume of blood for oxygen and nutrition, the body causes its heart to dilate or enlarge in size so that the smaller ejection fraction pumps about the same amount of blood. As noted, a normal heart with a blood capacity of seventy milliliters and an ejection fraction of sixty percent would pump approximately 42 milliliters per beat. The body seems to appreciate that this same volume per beat can be maintained by an ejection fraction of only thirty-percent if the ventricle enlarges to a capacity of 140 milliliters.
• FIG. 1 shows a cross sectional view of an enlarged human heart.
• congestive heart failure is a major cause of death and disability in the United States where approximately 400,000 cases occur annually.
• Post-infarction surgical re-vascularization can be directed at remote viable muscle to reduce ischemia. However, it does not address the anatomical consequences of the akinetic region of the heart that is scarred. Despite these techniques for monitoring ischemia, cardiac dilation and subsequent heart failure continue to occur in approximately fifty percent of post-infraction patients discharged from the hospital.
• the majority of blockages of the arteries are generally on the Left Anterior Descending (LAD) artery.
• LAD Left Anterior Descending
• This artery feeds the anterior portion of the heart and the apex.
• a blockage in this artery will lead to an infarction that includes an anterior portion of the heart along with the apex.
• the structure of the apex involves all walls of the ventricle, so that if the apex becomes akinetic it involves all the walls that make up the apex.
• the extent of each wall's involvement will differ, but the involvement will be in three dimensions and not limited to one wall of the ventricle.
• Various surgical approaches have been taken to repair the dilation that occurs after the apex and anterior wall of the left ventricle have had an infarction. These approaches are primarily intended to reduce the ventricular volume, while making an attempt to restore ventricular shape. Some of these procedures involve removing dyskinetic and akinetic regions of the heart, then surgically joining the viable portions of the myocardial walls, typically with the use of a patch surgically placed in the walls using a Fontan stitch.
• the Fontan stitch is a stitch placed on the border zone between akinetic and viable muscle, when tightened this stitch form a rim onto which the patch can be sewn.
• the patches that are used are constructed from flat, generally rectangular sheets of material.
• the correctly shaped patch to exclude tissue or cover a hole is cut from these rectangular sheets and sutured into place. Since the patch is flat, it tends to make the ventricle more spherical. This situation is illustrated in FIG. 2, which shows a cross-sectional view of human heart with a flat patch 200.
• ventricle is three-dimensional and it is being repaired with a flat or two dimensional patch.
• the apex of the left ventricle has a very small radius, so that when it's tissue dies due to infarction the dead tissue is present on all sides of the heart along with another portion of dead tissue on the anterior side.
• surgeons can either exclude all the tissue of the apex by placing their patch at an angle almost parallel to the mitral valve. This excludes the akinetic tissue, but results in making the ventricle spherical, potentially leading to mitral regurgitation and reducing ventricle efficiency, as illustrated in FIG. 2.
• This method of repairing the ventricle also eliminates the apex, which is a key component in the twisting and contracting of the ventricle. This method may also make the ventricle too small as the cavity is greatly reduced to exclude all the akinetic tissue.
• a patch may be used to repair a left ventricle of a human heart.
• the patch may have a predetermined shape.
• the patch has a shape that is substantially the same as the shape of a portion of the left ventricle. In other words, the patch has a conical shape with a round apex.
• the tip of the cone When inserted into a patient, the tip of the cone may act as an apex of the heart.
• the patch may assist in reforming or reconstructing a ventricle.
• the patch may assist in reforming a contour of a ventricle.
• the product may be made from a bio-prosthetic like a porcine or bovine pericardium, or a prosthetic material like polyester or PTFE. Such a product may be fabricated by weaving or knitting or by using one or more continuous sheets.
• the patch could have radiopaque markings.
• the patch could be made of ion exchange material, which can act as an artificial muscle.
• the procedure addresses the ability of the surgeon to perform a surgical ventricular repair procedure that allows the surgeon to ensure that he gets the intended size and shape of the ventricle with an apex while at the same time excluding all the akinetic and dyskinetic tissue.
• the procedure by excluding much, if not all, of the akinetic and dyskinetic tissue while allowing the surgeon to create the proper shape with an apex, significantly reduces stress on the heart muscle and improves surgical outcome.
• the procedure by being done with a precise device allows the surgeon to make the procedure repeatable and reliable. The device takes the variation out of the procedure.
• FIG. 1 An embodiment of a sectional view of dilated heart.
• FIG. 2 An embodiment of a sectional view of a dilated heart with a flat patch.
• FIG. 3 An embodiment of an apical patch.
• FIG. 4 An embodiment of an apical patch cut to be placed in a patient.
• FIG. 5 An embodiment of a sectional view of dilated heart with an apical patch.
• apical patch 300 which may be "cone shaped" similar to the lower portion of the left ventricle. This conical shape may be open at base 302 of the patch and have tip 304, which may function as a new apex after insertion into the patient.
• three-dimensional patch 300 may be made out of a single piece of material to make the patch seamless.
• Patch 300 may come in different sizes; sizes may correspond to a size of a shaping device or to the size of an appropriate ventricle. Patch 300 may be easily cut, so that surgeons can match the material to the akinetic area of the patients heart.
• FIG. 4 Patch 300 may be made from a polyester, for example a DacronTM like material. Such material is currently used for implantable prosthetics. Woven materials, such as polyesters, may be impregnated with materials which function to inhibit penetration of fluids such as blood. Materials which may be impregnated to inhibit leaking may include collagen.
• Patch 300 can be manufactured in a variety of methods known in textile manufacturing (e.g., bonding, weaving, cut to shape and sewing etc.).
• An embodiment may have the three dimensional patch made from ePTFE (expanded polytetrafluoroethylene).
• patch 300 may be formed from bioprosthetic Additionally it can be made out of bioprosthetic materials. Examples of bioprosthetic materials may include, but are not limited to, porcine cells and bovine cells.
• apical patch 300 may be made of synthetic material that when subjected to a stimulus flexes or contracts. Synthetic material which flexes/contracts in response to stimuli may aid in contraction of the left ventricle.
• patch 300 may be made out of ion exchange material. Ion exchange material may be coated with a noble metal, shape memory metals, and/or electrosensitive gels that deform in reaction to an electrical signal. Such a patch could be simulated to flex in synchronization with the cardiac cycle of a pacemaker or other implantable controller.
• a controller may be programmed transcutaneously and the amount of contraction may be controlled and adjusted.
• An energy source of the electric signal may come from a rechargeable battery that can be charged transcutaneously.
• An embodiment may have apical patch 300 made totally from biologic material that contracts and assists in the contraction of the ventricle.
• biologic material that contracts and assists in the contraction of the ventricle.
• Such an embodiment may be made from autologous cells, xeno transplant, cultured skeletal muscle cells, cultured bone marrow cells, cultured cardiac muscle cells, and/or cultured smooth muscle cells.
• a growth factor to stimulate tissue growth may be impregnated in the biologic material to be released over time.
• Patch 300 may also be a structure that is impregnated with biological material that contracts and assists in the contraction of the ventricle.
• the structure could be impregnated with skeletal muscle cells, bone marrow cells, cardiac muscle cells, and/or smooth muscle cells.
• the structure may be bioabsorable and may be absorbed by the body over time, leaving only the biological material.
• a growth factor may be impregnated in the structure to be released over time.
• three-dimensional patch 300 may have radiopaque markings in a predetermined pattern.
• Radiopaque markings may allow doctors to monitor the patch and its interaction with the surrounding tissue after insertion into the patient.
• a surgeon determines what size, shape and orientation he intends to reconstruct a ventricle (the "intended" or appropriate shape).
• the surgeon then opens the ventricle and notes the extent of the scar inside the ventricle.
• Patch 300 may be placed in the ventricle.
• a surgeon may mark the extent of the scar tissue on patch 300.
• Patch 300 may be removed. Upon removal excess material may be trimmed from patch 300.
• Patch 300 is placed back in the ventricle and the surgeon ensures that the apex of the patch is located at the apex of the ventricle.
• Patch 300 may be sutured into the ventricle, excluding much, if not all, of the akinetic tissue and creating a new apex. In some embodiments it may be possible and/or desirable to exclude all of the akinetic tissue.
• a surgeon may decide on the volume of the ventricle.
• the surgeon may use a shaping device and a matching apical patch.
• a Fontan stitch can placed on the border zone of the akinetic and viable tissue.
• the shaping device is introduced into the ventricle and the Fontan stitch is pulled tight. A portion of the shaping device projects out of the Fontan stitch.
• Apical patch 300 may be cut such that the shape of the patch matches the projection of the shaping device outside of the Fontan stitch. Cut patch 300 may be sewn to a portion of the heart hemostatically.
• the shaping device is removed prior to completely sewing patch 300. Such a procedure would yield a reconstructed ventricle of the size and shape that is substantially the same as the intended or appropriate shape.

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• Health & Medical Sciences (AREA)
• Cardiology (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Transplantation (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Vascular Medicine (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Prostheses (AREA)

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Cited By (12)

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• 2003
  • 2003-01-23 CA CA002473929A patent/CA2473929A1/en not_active Abandoned
  • 2003-01-23 WO PCT/US2003/001917 patent/WO2003061455A2/en not_active Application Discontinuation
  • 2003-01-23 EP EP03705870A patent/EP1474032A2/de not_active Withdrawn

Non-Patent Citations (1)

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