Abstract & Commentary
Leadless Pacemakers: Coming Soon to an Electrophysiology Lab Near You
By Edward P. Gerstenfeld, MD
Professor of Medicine, Chief, Cardiac Electrophysiology, University of California, San Francisco
Reddy VY, et al. Permanent leadless cardiac pacing: Results of the leadless trial. Circulation 2014; 129:1466-1471.
Implantable pacemakers have existed for decades. Although numerous "bells and whistles" have been added, the essential components of pacemakers have remained unchanged. The weakest link of pacemakers is the intracardiac leads. Acute complications of lead placement include pneumothorax and cardiac perforation; long-term complications include lead fracture, insulation break, and infection requiring device extraction.
In this early study, 33 patients underwent implantation of a novel leadless single-chamber cardiac pacemaker. The leadless pacemaker is a single capsule that contains the pacemaker electronics, battery, and electrodes. The leadless pacemaker is placed using an 18 Fr sheath delivery system advanced to the heart from the femoral vein. The pacing device is screwed into place in the right ventricular apex and the sheath removed. Special programming software allows communication and reprogramming of the pacemaker via electrodes placed on the patient’s skin. The estimated battery life is 8.4 years with 100% pacing and 12.4 years with 50% pacing.
Thirty-three patients (mean age 78 years, 67% male) with indications for single-chamber pacemaker underwent leadless pacemaker implantation. The implant success rate was 97% and the complication-free rate was 94%. One patient had a cardiac perforation and tamponade requiring cardiac surgery, and ultimately died. One patient had the device inadvertently implanted in the left ventricle; it was retrieved and implanted in the right ventricle. There were no vascular complications. Pacing thresholds, sensing, and impedance remained acceptable out to 12 weeks. The authors concluded that a self-contained, single-chamber, leadless cardiac pacemaker system is feasible and safe. The lack of a subcutaneous pulse generator and leads represent a major advance in cardiac pacemaking that could eliminate many long-term complications of conventional systems.
Earl Bakken developed the first wearable cardiac pacemaker in 1958. In 1964, Chardack and Greatbatch developed the first implanted pacemaker. The basics of cardiac pacemakers, a pulse generator attached via leads to the atrium and/or ventricles, have undergone miniaturization and electronic improvement, but little revolutionary change since then. The leadless pacemaker is potentially a major innovation in device therapy. Although the current version is only intended for single-chamber pacing, dual chamber and multisite pacing are sure to follow. The ability to wirelessly communicate and reprogram the pacemaker are major technologic achievements. Many issues remain to be determined. Hopefully, the one case of tamponade observed during the trial can be attributed to the "learning curve" of using a new device. However, most perforations that occur using standard leads are treatable with pericardiocentesis and do not require sternotomy. The risk of using the large 18 Fr catheter in the right ventricle to deploy the pacing device remains to be determined in larger studies. Although technology exists to remove the device if it is not positioned well, it is also unknown whether the device can be removed after 8-10 years when the battery is depleted. Removal of the device in case of infection has also never been tested. Stability of pacing parameters and the device itself requires longer-term follow-up. However, the leadless pacemaker clearly represents a revolution in pacing technology. One could imagine combining a subcutaneous defibrillator with leadless pacing to allow full functionality of antitachycardia pacing and defibrillation without leads. Placement of multiple devices to allow multisite pacing should also be feasible. A larger multicenter study of the single-chamber pacemaker is being planned. Stay tuned for future developments.