This Leadless Dual-Chamber Pacing System Is Coming
By Michael H. Crawford, MD, Editor
SYNOPSIS: The initial 90-day experience with a dual-chamber leadless pacemaker system showed reliable atrial pacing and atrioventricular synchrony, with complication rates similar to conventional lead-based systems.
SOURCE: Knops RE, Reddy VY, Ip JE, et al. A dual-chamber leadless pacemaker. N Engl J Med 2023;388:2360-2370.
Right ventricular (RV) leadless pacemakers cause fewer complications because they do not include a lead or a pocket. However, these systems cannot pace the atria or provide consistent atrioventricular synchrony. Recently, a dual-chamber bidirectional communication system has been developed to address these deficiencies.The initial safety and performance of this system in humans was the subject of a prospective, international, multicenter investigation of the first 300 patients in whom implantation of the system was attempted. The major inclusion criterion was the need for dual-chamber pacing in someone age 18 years or older. The exclusion criteria were mechanical prosthetic tricuspid valve, inferior vena cava filter, pre-existing pacer or defibrillator leads, and an active electronic medical device.
The dual-chamber system consists of a catheter-delivered, fully contained, fixed helix device that wirelessly communicates through the blood and myocardial tissue on a beat-to-beat basis to maintain atrioventricular synchrony. The primary safety endpoint was freedom from complications through 90 days of follow-up. The primary performance endpoints were a combination of adequate atrial capture threshold and atrial sensing amplitude, along with atrioventricular synchrony. The 300 patients were recruited from 55 centers in Canada, Europe, and the United States. Eighty-two different physicians implanted the devices.
Most patients exhibited either sinus node dysfunction (63%) or atrioventricular block (33%). Procedural success was achieved in 98%. Two patients did not go through with implantation. In three patients, the two devices failed to communicate. Severe procedure- or device-related complications occurred in 29 patients within the 90-day follow-up period. Most of the complications (80%) occurred within the first two days after implantation. The most common complications were atrial fibrillation (3%), along with spontaneous intraprocedural dislodgement (1.7%) and post-procedural dislodgement (1.7%). All other complications occurred at a frequency less than 1%. None of the patients required device revision for inadequate sensing, and at least 70% atrioventricular synchrony was achieved in 97% of the patients. The authors concluded a new dual-chamber leadless pacemaker system provided reliable atrial pacing and atrioventricular synchrony for three months after implantation, with 90-day complication rates similar to devices with leads.
This 90-day experience in humans with a dual-chamber leadless pacing system showed an implantation success rate of 98%. The device or procedure complication rate was 10%; in 90% of patients, atrial capture and sensing were adequate. Also, there were no system revisions required for inadequate atrial sensing, and 97% of patients demonstrated 70% or better atrial-ventricular synchrony. In addition, serious cardiac injury, such as pericardial effusion, occurred in only 0.7% of the study population. Finally, atrial device dislodgement occurred in 1.7% of patients, and ventricular device dislodgement occurred in 0.1%.
Atrial fibrillation would not be unexpected, considering a clinician attaches a device to the atrium. Surprisingly, it only occurred in nine patients, all but one of which occurred during the procedure. Of interest, five of the nine patients presented with a history of atrial fibrillation.
Both devices are cylinders, which are 6.5 mm in diameter with a helical attachment coil at one end. The atrial device is 32 mm in length, and the ventricular device is 38 mm long. The ideal attachment location was the base or ostium of the right atrial appendage. Insertion into the appendage was not as stable. The RV device was placed in the lower mid-interventricular septum, and only one dislodged during the procedure. Two of the devices that dislodged from the RA during the procedure traveled to the next chamber downstream — one to the pulmonary artery (PA), and one to the left ventricle, presumably through a patent foramen ovale. All five dislodgements post-procedure were identified a mean 26 days post-implantation. In four of these cases, the device had migrated to the either the RV or the PA. All dislodged devices were retrieved successfully. Only two systems were revised during follow-up: one because of suboptimal communication between the devices, and one for intermittent ventricular capture.
Consider these limitations: There was no control group, so no one received conventional lead-based systems. The follow-up was short. Although the FDA probably will require more long-term data, I will be surprised if this leadless dual-chamber system is not approved. After all, it completely eliminates lead- and pocket-related problems.
The initial 90-day experience with a dual-chamber leadless pacemaker system showed reliable atrial pacing and atrioventricular synchrony, with complication rates similar to conventional lead-based systems.
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