Leadless Cardiac Pacemakers: Back to the Future
Leadless Cardiac Pacemakers: Back to the Future
Despite significant advances in battery longevity, lead performance, and programming features since the first implanted permanent pacemaker was developed, the basic design of cardiac pacemakers has remained relatively unchanged over the past 50 years. Because of inherent limitations in their design, conventional (transvenous) pacemakers are prone to multiple potential short- and long-term complications. Accordingly, there has been intense interest in a system able to provide the symptomatic and potentially lifesaving therapies of cardiac pacemakers while mitigating many of the risks associated with their weakest link—the transvenous lead. Leadless cardiac pacing represents the future of cardiac pacing systems, similar to the transition that occurred from the use of epicardial pacing systems to the familiar transvenous systems of today. This review summarizes the current evidence and potential benefits of leadless pacing systems, which are either commercially available (in Europe) or under clinical investigation.
Since the first completely endocardial transvenous permanent pacemaker was implanted more than 50 years ago, significant advances have been made in battery longevity, lead performance, and device programming. Nevertheless, the basic design of cardiac pacemakers has remained relatively unchanged: a (most commonly) pectoral pulse generator connected to 1 or more transvenous leads. Although highly reliable, conventional cardiac pacemakers have several limitations. The subcutaneous pocket has a potential for local complications, such as skin erosion and pocket hematomas, which can be associated with a 15-fold higher risk for subsequent infection if early reintervention is required. The insertion of transvenous leads can result in acute complications, such as pneumothorax or upper extremity deep vein thrombosis, and the presence of chronic transvenous leads can lead to central vein obstruction, tricuspid valve insufficiency, and infection. Even for single-chamber transvenous systems (which are associated with a lower risk than dual-chamber system implants), more than 1 in every 40 implants will result in a complication requiring surgical intervention within the first 3 months, of which more than one-half are lead related. In the long term, lead failures are associated with significant morbidity.
Early recognition that transvenous leads are the weakest link of conventional pacing systems led investigators more than 40 years ago to consider the possibility of leadless cardiac pacing. A pre-clinical report in 1970 demonstrated the feasibility of a totally self-contained intracardiac pacemaker. In that study, a canine with an iatrogenic heart block was paced for more than 2 months. The delivery catheter was inserted through the jugular vein, the leadless pacemaker was passed into the right ventricle under fluoroscopy, and radially directed spiral barbs attached the cylindrical device to the ventricular myocardium. Approximately 2 decades later, additional pre-clinical testing again demonstrated the potential feasibility of this approach. Although the field of leadless cardiac pacing remained stagnant for almost 20 years, this has changed with the advent of advancements in several areas, including catheter-based delivery systems, miniaturized high-density energy sources, low-power electronics, novel packaging capabilities, and novel communication technologies. In this review, we strive to summarize the current state of the 2 basic designs of leadless cardiac pacemakers (LCPs). One design uses 2 separate components, an endocardial pacing electrode and a subcutaneous energy transmitter, whereas the second design is a completely self-contained device in which the pulse generator and pacing electrode are a single component.
Abstract and Introduction
Abstract
Despite significant advances in battery longevity, lead performance, and programming features since the first implanted permanent pacemaker was developed, the basic design of cardiac pacemakers has remained relatively unchanged over the past 50 years. Because of inherent limitations in their design, conventional (transvenous) pacemakers are prone to multiple potential short- and long-term complications. Accordingly, there has been intense interest in a system able to provide the symptomatic and potentially lifesaving therapies of cardiac pacemakers while mitigating many of the risks associated with their weakest link—the transvenous lead. Leadless cardiac pacing represents the future of cardiac pacing systems, similar to the transition that occurred from the use of epicardial pacing systems to the familiar transvenous systems of today. This review summarizes the current evidence and potential benefits of leadless pacing systems, which are either commercially available (in Europe) or under clinical investigation.
Introduction
Since the first completely endocardial transvenous permanent pacemaker was implanted more than 50 years ago, significant advances have been made in battery longevity, lead performance, and device programming. Nevertheless, the basic design of cardiac pacemakers has remained relatively unchanged: a (most commonly) pectoral pulse generator connected to 1 or more transvenous leads. Although highly reliable, conventional cardiac pacemakers have several limitations. The subcutaneous pocket has a potential for local complications, such as skin erosion and pocket hematomas, which can be associated with a 15-fold higher risk for subsequent infection if early reintervention is required. The insertion of transvenous leads can result in acute complications, such as pneumothorax or upper extremity deep vein thrombosis, and the presence of chronic transvenous leads can lead to central vein obstruction, tricuspid valve insufficiency, and infection. Even for single-chamber transvenous systems (which are associated with a lower risk than dual-chamber system implants), more than 1 in every 40 implants will result in a complication requiring surgical intervention within the first 3 months, of which more than one-half are lead related. In the long term, lead failures are associated with significant morbidity.
Early recognition that transvenous leads are the weakest link of conventional pacing systems led investigators more than 40 years ago to consider the possibility of leadless cardiac pacing. A pre-clinical report in 1970 demonstrated the feasibility of a totally self-contained intracardiac pacemaker. In that study, a canine with an iatrogenic heart block was paced for more than 2 months. The delivery catheter was inserted through the jugular vein, the leadless pacemaker was passed into the right ventricle under fluoroscopy, and radially directed spiral barbs attached the cylindrical device to the ventricular myocardium. Approximately 2 decades later, additional pre-clinical testing again demonstrated the potential feasibility of this approach. Although the field of leadless cardiac pacing remained stagnant for almost 20 years, this has changed with the advent of advancements in several areas, including catheter-based delivery systems, miniaturized high-density energy sources, low-power electronics, novel packaging capabilities, and novel communication technologies. In this review, we strive to summarize the current state of the 2 basic designs of leadless cardiac pacemakers (LCPs). One design uses 2 separate components, an endocardial pacing electrode and a subcutaneous energy transmitter, whereas the second design is a completely self-contained device in which the pulse generator and pacing electrode are a single component.
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