BACKGROUND

The present invention relates generally to cardiac pacing. More particularly, the invention describes novel devices and methods of physiologic cardiac stimulation using a multi-electrode cardiac pacemaker configured for stimulating ventricular intraseptal area of the heart engaging the natural conduction pathways in the cardiac septum.

His bundle pacing has emerged recently as a useful alternative to traditional single- and multi-chamber pacemaker configurations, especially as a good physiologic alternative to right ventricular pacing. In studies, His bundle pacing has been shown to be associated with a significant reduction in mortality as well as various complications such as heart failure hospitalizations and upgrade to bi-ventricular pacing in comparison to right ventricle pacing in patients with bradycardia and indications for permanent pacemakers (see for example Sharma PS, etc. Permanent His bundle pacing is feasible, safe, and superior to right ventricular pacing in routine clinical practice.Heart Rhythm.2015; 12(2):305-312). Based on a systematic review of the available published literature on physiologic pacing, HBP was incorporated into the recently released 2018 American Heart Association/American College of Cardiology/Heart Rhythm Society guidelines on the evaluation and management of patients with bradycardia and cardiac conduction delay.

At the same time, while His bundle pacing is feasible in the majority of patients requiring ventricular pacing, it may be more challenging to implement in some patients due to existence of high capture thresholds or an inability to correct underlying His-Purkinje conduction disease (see for example Vijayaraman P. His bundle pacing to left bundle branch pacing: evolution of His-Purkinje conduction system pacing.The Journal of Innovations in Cardiac Rhythm Management,2019; 10:3668-3673).

FIGS. 1 and 2illustrate that this can be explained by the position of the source of conduction abnormalities22located distally of the AV node10and His bundle20.FIG. 1shows the right atrium and intraseptal conduction pathways andFIG. 2shows how conduction pathways bifurcate distally of the His bundle into right bundle branch12and left bundle branch14, which in turn also splits into Left Posterior Fascicle16and Left Anterior Fascicle18.

To overcome this condition, pacing of left bundle branch14and/or right bundle branch12at locations distal of the conduction abnormality22may be implemented by positioning the pacing electrodes at the intraseptal area of the heart between the right ventricle and left ventricle, see for example positions12and14inFIG. 1as examples of such locations.

As discussed in my earlier patent applications, deployment of a pacing electrode aimed to reach intended conduction fibers such as His bundle and provide for pacing with a low capture threshold may be difficult to achieve. Multiple placements of such electrode may be attempted before achieving a satisfactory result. The need therefore exists for devices and methods for improved deployment and operation of cardiac pacemakers configured for stimulation of left and/or right bundle branches of the heart at a location defined by the heart interventricular septum representing a target, which may be easier to reach with a single deployment.

A further uncertainty during deployment of a conventional electrode when used for intraseptal pacing is the location of the conduction fibers for one of both branches of the His bundle. For each branch, it is uncertain as to where the fibers are located so as to minimize the capture threshold. This location uncertainty may be divided into a lateral position uncertainty (radially away from the center of the delivery system) as the electrode is approaching the septal surface and a depth uncertainty as such conduction pathway fibers may be positioned at various depths inside the septum of the heart.

Septum thickness is limited as well as electrode deployment would be done best if it does not protrude/perforate across the septum and emerges on the opposite side of the septal wall. Anatomical variations between subjects may make if difficult to design one or just a few sizes of such electrodes for use with most subjects.

The need exists therefore for a universal design of intraseptal pacemaker configured to be used in most cases without the risk of “under-deployment” or “over-deployment” into the septal tissue.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to overcome these and other drawbacks of the prior art by providing a novel intraseptal multi-electrode cardiac pacemaker configured for electrical stimulation of the heart at an intraseptal location.

It is another object of the present invention to provide either a single-conduit or leadless intraseptal multi-electrode pacemaker configured for implantation at an interventricular septum of the heart in a broad range of patients with a variety of anatomical variations and abnormalities in electrical conduction of the cardiac tissue.

A further object of the present invention is to provide an intraseptal multi-electrode cardiac pacemaker allowing to rapidly identify best stimulation sites after implantation and to provide cardiac pacing without a need to implant multiple individual electrodes.

It is yet another object of the present invention to provide an intraseptal multi-electrode pacemaker configured to stimulate not only one or two ventricles of the heart but also for synchronized stimulation of the right atrium of the heart using the same control unit.

Finally, it is a further object of the present invention to provide a combination of a cardiac pacemaker and an implantable cardioverter/defibrillator, which can be activated as needed or at a later date after activation of the pacemaker for providing heart stimulation therapy to the subject along with lifesaving defibrillation therapy.

In embodiments, the novel intraseptal multi-electrode pacemaker comprises a flexible elongated conduit containing at least a first plurality of individual electrical wires (such as electrical wires120and150inFIG. 3) operably connected to a plurality of respective first individual electrodes (such as individual electrodes122and152inFIG. 3) at the distal end of the flexible conduit. In other embodiments, the elongated conduit may also house a second plurality of individual electrical wires operably connected to a respective plurality of second individual electrodes. The plurality of first electrodes extend from the distal end of the conduit by a first distance selected to provide implantation of first electrodes at a depth generally corresponding to a presumed location of conductive fibers of the left bundle branch in the interventricular septum. At the same time, the plurality of second electrodes may be configured to extend from the distal end of the flexible conduit at a second distance selected to implant second electrodes at a depth generally corresponding to a presumed intraseptal location of conduction fibers of the right bundle branch of His bundle. The flexible conduit may further be equipped with a tissue fixation screw, which by itself may house no electrodes, while in other embodiments it may house one or more pacing and/or sensing electrodes.

Following the positioning of the first and/or second pluralities of individual electrodes in and around the target area of the cardiac septum, for example approaching the septum from the right ventricle, individual interrogation of these individual electrodes may be conducted with the aim of identifying selected electrodes located directly at the target site of either the left bundle branch or the right bundle branch, or both. Selected subsets of individual electrodes may be identified as preferred for subsequent cardiac stimulation based on one or more predetermined criterion, for example an intraseptal capture threshold of the LV or RV myocardium via the corresponding bundle branches at or below a predetermined level. Those individual electrodes that do not provide desired cardiac stimulation response during test stimulation may be abandoned and left in a passive state inside the cardiac tissue. If more than one individual electrode is found to satisfy the desired selection criterion, additional selection within this group may be conducted to identify one or more individual electrodes with the lowest capture threshold for effective cardiac stimulation.

The step of re-evaluating some or all of the individual electrodes may be repeated from time to time, for example when a failure of one or more of the individual electrodes is detected. Upon completion of such re-evaluation, the same or a different subset of individual electrodes may be selected to provide pacing therapy to the heart of the subject.

In further embodiments, additional atrial electrodes may be provided for stimulating a right atrium of the heart so that the entire cardiac pacing therapy may be delivered from a single control unit. Such one or more additional individual electrodes may be configured for implantation into a variety of subjects with a broad range of anatomical variations and still provide at least one atrial electrode with an acceptable cardiac pacing performance.

Finally, a combination of a multi-electrode cardiac pacemaker and an implantable cardioverter/defibrillator is described in which one or more defibrillator coils may be positioned at the distal end of the flexible conduit and used as a mechanical stop to limit the depth of implantation of the multiple individual electrodes of the cardiac pacemaker. In further embodiments, one or more of the coils of the defibrillator portion of the device may be used as intermittently- or continuously-operated sensing electrodes during the initial evaluation and/or subsequent use of the pacemaker electrodes.

