A newly released comparative analysis shows that a leadless cardiac pacemaker may hold safety advantages over traditional transvenous cardiac pacemakers.
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The analysis, presented May 6 as a late-breaking paper at the 37th annual scientific sessions of the Heart Rhythm Society (HRS), compared acute and mid-term adverse event rates from the multicenter LEADLESS II clinical trial of St. Jude Medical’s Nanostim™ leadless pacemaker with those seen for transvenous pacemakers from a large U.S. insurance claims database. Patients receiving the leadless device in the clinical trial developed significantly fewer infectious and lead-related complications than did those implanted with transvenous pacemakers in real-world settings.
Surprisingly, complication rates in the real-world claims data were higher than previously reported for transvenous devices. “The findings suggest a possible disconnect between true real-world complication rates for transvenous pacemakers and those previously reported in the literature,” says Cleveland Clinic electrophysiologist and LEADLESS II investigator Daniel J. Cantillon, MD, who is a co-author on the HRS study presentation.
Just one-tenth the size of traditional pacemakers, leadless pacemakers are fully self-contained devices implanted within the right ventricle nonsurgically using a catheter introduced via a vein in the leg. One of these devices, Medtronic’s Micra® Transcatheter Pacing System, was approved by the FDA in early April, and approval of the Nanostim is expected soon.
Interim LEADLESS II data on 300 Nanostim recipients with a minimum six months of follow-up were published in the New England Journal of Medicine in September 2015, as recapped in this Consult QD post. In the new analysis, data on 718 Nanostim recipients from LEADLESS II followed for a mean of 11 months were compared with those of 10,521 recipients of transvenous pacemakers (any manufacturer) from the Truven MarketScan® database.
Within one month of implant, 5.8 percent of the LEADLESS II patients developed complications, which included device dislodgement in 1 percent of patients and pericardial infusion in 1.5 percent of patients.
In contrast, acute complications occurred in 12.7 percent of the transvenous pacemaker group, including lead-related adverse events in 7.6 percent, thoracic trauma in 3.9 percent, and infection in 1.9 percent. Those types of complications don’t apply to leadless pacemakers, notes Dr. Cantillon, who performed one of the first implantations of the Nanostim device in the U.S., in Feb. 2014.
Mid-term complications (between one month and two years) were rare among the LEADLESS II cohort (0.6 percent incidence) but were seen in 5.4 percent of transvenous pacemaker recipients, including additional lead-related adverse events in 2.4 percent and infection in 2.6 percent.
To date, Cleveland Clinic has had no complications with the leadless device.
The 7.6 percent rate of acute lead-related complications is more than double the 3.3 percent reported in a prior clinical trial of transvenous pacemakers. While high-volume centers such as Cleveland Clinic have been able to achieve and publicly report very low complication rates with transvenous pacemakers, on the order of 1 to 2 percent acutely, “this analysis suggests that many centers may have very high complication rates by comparison,” Dr. Cantillon says.
So why were clinical trial results compared with real-world data, rather than studying the two devices in controlled head-to-head trials?
For one, Dr. Cantillon explains, current leadless pacemakers can provide only single-chamber (right ventricular) pacing support, which accounts for 10 percent or less of individuals who need cardiac pacing. “Practically speaking, it would be difficult to divide an already small niche by randomizing them between transvenous and leadless devices,” he says.
Secondly, he notes, it’s common for novel technologies to be evaluated initially without randomization to establish safety and effectiveness while allowing technological refinement based on early experience.
Dr. Cantillon is quick to add that future real-world data on leadless pacemakers might also yield less positive findings: “Who’s to say that claims data won’t one day reflect higher real-world complications for leadless pacemakers than those reported in the clinical trials? That’s a legitimate concern as FDA approval increases device availability outside the relatively few elite centers participating in the trials.”
Nonetheless, he maintains that this analysis “debunks the argument that leadless pacing is unnecessary because complications with transvenous systems are very low across the board. Leadless pacing can potentially eliminate the most common sources of complications, which are the surgical pocket and the lead. Those are significant, and should — by definition — disappear with leadless devices.”