Leadless Pacemaker Shown Safe in Older, Sicker Patients

Mitchel L. Zoler

May 20, 2020

A leadless right-ventricular pacemaker continued to show an edge over conventional transvenous pacemakers by triggering a substantially reduced rate of complications during the 6 months following placement in a review of more than 10,000 Medicare patients treated over 2 years.

The "largest leadless pacemaker cohort to date" showed that in propensity score–matched cohorts, the 3,276 patients who received the Micra leadless transcatheter pacemaker during routine management and were followed for 6 months had a 3.3% rate of total complications, compared with a 9.4% rate among 7,256 patients who received a conventional VVI pacemaker with a transvenous lead, a statistically significant 66% relative risk reduction, Jonathan P. Piccini, MD, said at the annual scientific sessions of the Heart Rhythm Society, held online because of COVID-19.

The 66% reduced rate of complications — both acutely and with further follow-up — was similar to the complication reductions seen with Micra, compared with historical controls who received transvenous single-chamber pacemakers in both the pivotal study for the device (Heart Rhythm. 2017;14[3]:702-9) and in a postapproval registry study (Heart Rhythm. 2018;15[12]:1800-7). However, the newly reported advantage came in a population that was notably older and had significantly more comorbidities than in the prior leadless pacemaker studies, said Dr. Piccini, a cardiac electrophysiologist at Duke University, Durham, N.C.

The new Medicare data "tell us that physicians are reaching for these devices [leadless pacemakers] in patients with more comorbidities and a higher risk for complications to give them a [device with] better safety profile," he said during a press briefing. "At Duke, and I suspect at other centers, when a patients is eligible for a leadless pacemaker that's the preferred option."

However, Dr. Piccini cited three examples of the small proportion of patients who are appropriate for the type of pacing the leadless pacemaker supplies but would be better candidates for a device with a transvenous lead: patients who failed treatment with an initial leadless pacemaker and have no suitable alternative subcutaneous spot to place the replacement device in a stable way, those with severe right ventricular enlargement that interferes with optimal placement, and those who don't currently meet criteria for biventricular pacing but appear likely to switch to that pacing mode in the near term.

The 66% relative reduction in complications was "impressive; I hope this will be a message," commented Nassir F. Marrouche, MD, a cardiac electrophysiologist and professor of medicine at Tulane University, New Orleans. Importantly, this reduced complication rate occurred in a real-world population that was sicker than any patient group previously studied with the device, he noted as a designated discussant for the report.

But the report's second designated discussant, Roderick Tung, MD, highlighted some caveats when interpreting the lower complication rate with the leadless device compared with historical controls. He cited the absence of any episodes of pneumothorax among the patients reviewed by Dr. Piccini who received a leadless pacemaker, compared with a 5% rate among the control patients who had received a device with a transvenous lead, a major driver of the overall difference in complication rates. This difference "may not be relevant to operators who use either an axillary extrathoracic vein route for lead placement or a cephalic vein approach," said Dr. Tung, director of cardiac electrophysiology at the University of Chicago. "There should not be a 5% rate of pneumothorax when implanting a VVI device." The results reported by Dr. Piccini have the advantages of coming from many patients and from real-world practice, he acknowledged, but interpretation is limited by the lack of a randomized control group and the outsized impact of pneumothorax complications on the safety comparison.

The other major component of the 6-month complication tally was device-related events, which were twice as common in the historical controls who received a transvenous lead at a rate of 3.4%. The sole 6-month event more common among the patients who received a leadless pacemaker was pericarditis, at a rate of 1.3% in the Micra group and 0.5% in the transvenous lead controls, Dr. Piccini reported. The 6-month rate of device revisions was 1.7% with the leadless device and 2.8% with transvenous lead pacemakers, a difference that was not statistically significant. The two treatment arms had virtually identical 6-month mortality rates.

The rate of acute complications during the first 30 days after implant was also virtually the same in the two study arms. Patient who received the leadless device had significantly more puncture-site events, at a rate of 1.2%, and significantly more cardiac effusions or perforations, at a rate of 0.8%. The historical control patients who received devices with transvenous leads had significantly more device-related complications after 30 days, a 2.5% rate.

The 30-day cohorts examined had larger numbers of patients than at 6 months, 5,746 leadless pacemaker recipients and 9,662 matched historical controls who had received a transvenous lead pacemaker. The clinical and demographic profile of the 30-day cohort who received the leadless pacemaker highlighted the sicker nature of these patients compared with earlier studies of the device. They were an average age of 79 years, compared with average ages of 76 years in the two prior Micra studies, and they also had double the prevalence of coronary disease, triple the prevalence of heart failure, more than twice the rate of chronic obstructive pulmonary disease, and almost twice the prevalence of diabetes.

During the period examined in this report from Micra CED (Longitudinal Coverage With Evidence Development Study on Micra Leadless Pacemakers), in 2017-2018, the leadless pacemaker's initial approved indications were for a circumscribed portion of the overall patient population that needs pacing. Essentially, they were elderly patients with persistent atrial fibrillation who only need ventricular pacing, roughly 15% of the overall cohort of pacing candidates. In January 2020, the FDA added an indication for high-grade atrioventricular block, an expanded population of candidates that roughly tripled the number of potentially appropriate recipients, said Larry A. Chinitz, MD, a cardiac electrophysiologist and a coinvestigator on some of the studies that led to the new indication, in an interview at the time of the revised labeling.

The study was sponsored by Medtronic, which markets the Micra leadless pacemaker. Dr. Piccini has received honoraria from Medtronic and several other companies. Dr. Marrouche has been a consultant to Medtronic as well as to Biosense Webster, Biotronik, Cardiac Design, and Preventice, and has received research funding from Abbott, Biosense Webster, Boston Scientific, and GE Healthcare. Dr. Tung has been a speaker on behalf of Abbott, Boston Scientific, and Biosense Webster. Dr. Chinitz has received fees and fellowship support from Medtronic, and has also received fees from Abbott, Biosense Webster, Biotronik, and Pfizer.

Heart Rhythm Society (HRS) 2020 Scientific Sessions: Abstract D-LBCT04-01. Published online May 8, 2020.

Mitchel L. Zoler can be reached at mzoler@mdedge.com. This article originally appeared on MDedge.

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