GB2615090A - Improvements in or relating to cardiac pacemakers - Google Patents

Abstract

Medical electrode or conduction lead arrangement comprising a leg 20 which can be folded from collapsed state to provide radial expansion upon relative rotation of the leg and an internal thread. A conduction system pacing lead is provided and comprises a multicore, multipolar lead. The lead comprises one or more hinged legs 20 at a distal portion, and an active fixation helix integral with a length of threaded internal core. In an initial position, for delivery to the heart, the legs lie flat along the axis of the lead. Once a suitable position is identified, the fixation helix is deployed by rotation. Rotating the helix mechanism also turns the internal thread causing the legs to axially retract and buckle at hinged portions to deploy to a position generally perpendicular to the lead axis. The hinge points can contact the internal surface of the heart wall. Electrodes at each hinge point are now able to act as either cathode or anode.

Description

IMPROVEMENTS IN OR RELATING TO CARDIAC PACEMAKERS

The present invention relates generally to cardiac pacemakers and particularly, although not exclusively, to His Bundle and conduction system pacing.

Background

A cardiac pacemaker is a medical device that generates electrical impulses delivered by electrodes to cause the heart muscle chambers to contract and therefore pump blood; by doing so this device replaces and/or regulates the function of the electrical conduction system of the heart.

The primary purpose of a pacemaker is to maintain an adequate heart rate, either because the heart's natural pacemaker is not fast enough, or because there is a block in the heart's electrical conduction system. An additional functionality for some pacemaker systems attempts to overcome mechanical dyssynchrony between the two sides of the heart, and therefore improve the cardiac pumping efficiency.

Pacemaker systems have been the mainstay of treatment for significant slow heart rhythms for many years. The technology has evolved over time, but the system consists of a pulse generator (the "box" containing a battery and computer hardware) and one or more leads that traverse the major veins into the heart. The lead allows delivery of an electrical impulse from the pulse generator to the heart muscle, and this in turn triggers cardiac muscle contraction. The lead(s) also provide the system with the facility to sense intrinsic electrical activity from the heart, and respond appropriately.

Correct function of the system as a whole requires the lead(s) to be stable in position within the cardiac chamber: an unstable position may mean that electrical signals cannot be sensed appropriately, and/or that a paced beat cannot be successfully delivered. There are two widely used means of fixing the tip of the lead in place: 1. Passive fixation: the tip of the lead has backward pointing tines in an arrowhead arrangement, designed to snag into endocardial tissue in the manner of a grappling hook 2. Active fixation: the tip of the lead contains a helix, and this can be wound out into the endocardial tissue by rotation of an inner core from the far end of the lead.

The electrical circuit between the pacemaker system and the heart muscle can be configured either in a unipolar or bipolar arrangement. The cathode is generally an electrode at the tip of the lead, with the anode being either a ring electrode a short distance back from the tip (bipolar configuration), or the pulse generator can itself (unipolar configuration). The tip cathode may be a true electrode independent of the active fixation helix, or the helix may serve as both the electrode and fixation mechanism (the so-called "hot screw").

His Bundle Pacinq (HBP)/Conduction System Pacinq Conduction system pacing (CSP) is a technique of pacing that involves implantation of permanent pacing leads along different sites of the cardiac conduction system and includes His bundle pacing and left bundle branch pacing.

The Bundle of His or His bundle is a collection of heart muscle cells specialised for electrical conduction -see Figure 1. It is an integral part of the heart electrical conduction system. It transmits electrical pulses from the atrioventricular node (AV node) to the ventricles of the heart.

Conventional pacing of the right ventricle provides an extremely robust and successful way of treating slow heart rates. In recent years however, it has become increasingly apparent that in a proportion of patients (potentially -50%), the inherent nature of paced heartbeats causing mechanical dyssynchrony between the left and right sided heart chambers, in turn leads to weakening of heart muscle, and ultimately heart failure. This is recognised as pacing-induced cardiomyopathy (PICM). It is also associated with an increased risk of further abnormal heart rhythms. From a clinical perspective this has meant a search for alternative modalities of delivering pacing to the ventricles, and in particular the concomitant utilisation of the intrinsic conduction system of the heart: His Bundle pacing, or HBP. There is increasing adoption of this technique for patients perceived of being at high risk of developing PICM, or as a treatment option for those who have already developed it. Similar techniques are under evaluation for use in equivalent conduction tissue in the atria.

Although HBP is a very successful technique, it does have limitations. Primarily these relate to the lead and its position within the heart. The most widely utilised system currently is the Medtronic Select Secure lead. This is a relatively small diameter multicore lead that uses the hot-screw fixation technique, and is positioned by deployment through a pre-shaped catheter. Once an appropriate position is identified, the catheter is slit and removed, leaving the lead fixed in place. The difficulties arise through identification of an appropriate target area for lead deployment, and the possibility that the electrical characteristics of this and the surrounding tissue change over time. A substantial change in electrical characteristics would require extraction of the lead and delivery of a replacement to an adjacent target area. The target area is only a few square millimetres, meaning that lead delivery has to be extremely accurate despite the challenges inherent in manipulating a catheter within a heart moving in three dimensions with cardiac contraction and the respiratory cycle. The procedural failure rate is approximately 10% at implant, with a further 5-10% developing lead issues in the longer term.

His Bundle Capture Successful electrical capture of the His bundle requires delivery of a pacing stimulus of sufficient strength and duration to do so (known as "capture"). The area of tissue captured by a stimulus is proportional to the size of the electrical impulse, and the size of the electrode at the lead tip. An increase in lead tip diameter would enlarge the target area, but large diameter leads are more difficult to position, and more prone to mechanical failure in the long term. There are also associated long term complications from occlusion of the veins used to access the heart for lead delivery. Equally, although very high output impulses can effectively enlarge the target area, this drains the pacemaker battery at a disproportionate rate, and is often unsuitable for clinical practice.

Multipolar Leads A similar difficulty is encountered with the techniques utilised in cardiac resynchronisation pacemakers: these have leads delivered through small veins running over the outside of the heart, and again positioning into small target areas has been historically challenging. In this instance, success rates have been significantly improved by the introduction of leads that have four electrodes positioned longitudinally along the axis of the lead (see Figure 2). This allows for multiple combinations of anode and cathode, in both unipolar and bipolar configurations, and hence increases the chance of successful delivery into a target area whilst providing a degree of protection against microdisplacement.

The present invention seeks to provide improvements in or relating to conduction system pacing.

Surnmary An aspect of the present invention provides an electrode placement device for a pacemaker system, the device comprising one or more electrodes, the or each electrode is carried on or by a deployment member, the or each deployment member is movable from an undeployed position to a deployed position.

The or each deployment member may be configured to collapse so as to move from the undeployed position to the deployed position.

The or each deployment member may be formed as a collapsing leg.

The deployment member may be configured to collapse by, for example, including a hinge line, line of weakening or the like.

The device may further comprise fixation means. The device may, for example, be formed to have screw-in capability. A fixation helix or the like may be provided.

The deployment member may be caused to deploy as a consequence of the fixation means.

In some embodiments a plurality of electrodes are provided.

In some embodiments a plurality of deployments members are provided.

The or each deployment member may be provided with one or more electrodes.

The device may be provided as part of a lead, for example a multicore, multipolar lead. In other embodiments the device/mechanism is provided as part of a leadless pacemaker system.

The device may be provided in combination with a pulse generator.

A further aspect provides a conduction system (e.g. a His bundle) pacing lead comprising a multicore, multipolar lead, the lead comprising one or more hinged legs at a distal portion, and an active fixation helix integral with a length of threaded internal core, in which in an initial position, for delivery to the heart, the leg/s lie along the axis of the lead and in which once a suitable position is identified the fixation helix is deployed, in which rotation of the helix mechanism also rotates the internal thread, causing the leg/s to buckle at hinged portions, and deploy to a position generally perpendicular to the lead axis, and in contact with the internal surface of the heart wall.

The electrodes at each hinge point may be able to act as either cathode or anode in any combination.

Reversal of the torque on the helix may unwind the internal screw, restoring the legs to their original position, and freeing the distal helix fixation to allow redeployment in an alternative position.

The present invention also provides a pacemaker system comprising one or more devices as described herein or a lead as described herein.

One embodiment arranges multipolar electrodes in a fashion perpendicular to the lead axis, thus expanding the footprint of potential electrical capture in the target area, without requiring a substantial increase in lead diameter.

Embodiments may be based around a conventional multicore multipolar lead, delivered either through a pre-shaped catheter, or over a central stylet, but with a variable number of hinged legs at the distal portion, and an active fixation helix integral with a short length of threaded internal core. In the initial position, for delivery to the heart, the legs lie along the axis of the lead. Once a suitable position is identified, the fixation helix is deployed. The rotation of the helix mechanism also rotates the internal thread, causing the legs to buckle at the hinged portions, and deploy to a position perpendicular to the lead axis, and in contact with the internal surface of the heart wall. The electrodes at each hinge point are now able to act as either cathode or anode in any combination. If necessary, reversal of the torque on the helix unwinds the internal screw, restoring the legs to their original position, and freeing the distal helix fixation to allow redeployment in an alternative position.

Aspects and embodiments of the present invention may be applicable to lead-based and/or leadless pacemaker systems.

Different aspects and embodiments of the invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combination other than those explicitly set out in the claims. Each aspect can be carried out independently of the other aspects or in combination with one or more of the other aspects.

The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings.

Example embodiments are shown and described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate. The invention is not limited in the design and shape of the structure shown in the drawings.

The terminology used herein to describe embodiments is not intended to limit the scope. The articles "a," "an," and "the" are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including," when used herein, specify the presence of stated features, items, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealized or overly formal sense unless expressly so defined herein.

The embodiment illustrated in Figures 3 to 5 is based around a conventional multicore multipolar lead deliverable, for example, through a pre-shaped catheter or over a central stylet.

The lead has a number of hinged legs at its distal portion, and an active fixation helix integral with a short length of threaded internal core.

In the initial position (Figure 1), for delivery to the heart, the legs lie along the axis of the lead.

Once a suitable position is identified, the fixation helix is deployed. The rotation of the helix mechanism also rotates the internal thread, causing the legs to buckle at the hinged portions (Figure 4), and deploy to a position perpendicular to the lead axis (Figure 5), and in use in contact with the internal surface of the heart wall.

The electrodes at each hinge point are now able to act as either cathode or anode in any combination. If necessary, reversal of the torque on the helix unwinds the internal screw, restoring the legs to their original position, and freeing the distal helix fixation to allow redeployment in an alternative position.

This embodiment arranges multipolar electrodes in a fashion perpendicular to the lead axis, thus expanding the footprint of potential electrical capture in the target area, without requiring a substantial increase in lead diameter.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims (15)

1. CLAIMS1. An electrode placement device for a pacemaker system, the device comprising one or more electrodes, the or each electrode is carried on or by a deployment member, the or each deployment member is movable from an undeployed position to a deployed position.
2. 2. A device as claimed in claim 1, in which the or each deployment member is configured to collapse so as to move from the undeployed position to the deployed position.
3. 3. A device as claimed in claim 1 or claim 2, in which the or each deployment member is formed as a collapsing leg.
4. 4. A device as claimed in any preceding claim, further comprising fixation means.
5. 5. A device as claimed in claim 5, in which the fixation means comprises a fixation helix.
6. 6. A device as claimed in any preceding claim, in which a plurality of electrodes are provided.
7. 7. A device as claimed in any preceding claim, in which a plurality of deployments members are provided. 25
8. 8. A device as claimed in any preceding claim and provided as a lead.
9. 9. A device as claimed in claim 8, comprising a multicore, multipolar lead.
10. 10. A device as claimed in any of claims 1 to 7 and provided as a leadless pacemaker system.
11. 11. A device as claimed in any preceding claim in combination with a pulse generator.
12. 12. A conduction system pacing lead comprising a mulficore, multipolar lead, the lead comprising one or more hinged legs at a distal portion, and an active fixation helix integral with a length of threaded internal core, in which in an initial position, for delivery to the heart, the leg/s lie along the axis of the lead and in which once a suitable position is identified the fixation helix is deployed, in which rotation of the helix mechanism also rotates the internal thread, causing the leg/s to buckle at hinged portions, and deploy to a position generally perpendicular to the lead axis, and in contact with the internal surface of the heart wall.
13. 13. A lead as claimed in claim 12, in which the electrodes at each hinge point are able to act as either cathode or anode in any combination.
14. 14. A lead as claimed in claim 12 or claim 13, in which reversal of the torque on the helix unwinds the internal screw, restoring the legs to their original position, and freeing the distal helix fixation to allow redeployment in an alternative position.
15. 15. A pacemaker system comprising one or more devices as claimed in any of claims 1 to 11 or a lead as claimed in any of claims 12 to 14.