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Patients who got the Nanostim leadless pacemaker instead of a transvenous one had fewer complications through up to 18 months of follow-up, researchers said.

Those receiving the leadless cardiac pacemaker (LCP) generally had fewer complications than peers implanted with conventional transvenous pacemakers (adjusted HR 0.44, 95% CI 0.32-0.60), both for short-term complications within a month of device placement (5.8% versus 9.4%, P=0.01) and for mid-term events up to 18 months (0.56% versus 4.9%, P<0.001), Daniel Cantillon, MD, of Cleveland Clinic, and colleagues found in a propensity score-matched analysis.

Moreover, this advantage was observed across subgroups, the researchers reported online in .

"The overall reduction in both short- and mid-term events was driven by a virtual elimination of lead, pocket, and infectious complications, suggesting that this disruptive technology has successfully targeted the most common sources of traditional pacemaker complications observed over the past 50 years," Cantillon's group said.

But reducing those complications came with a trade-off: higher risk of cardiac perforations/pericardial effusions (1.53% versus 0.35%, P=0.005). Nanostim recipients also saw no reduction in vascular events (1.11% versus 0.42%, P=0.085), electrode dislodgement (0.97% versus 1.39%, P=0.54), or generator complications (0.70% versus 0.28%, P=0.17).

For the study, the investigators compared Nanostim recipients from the LEADLESS II IDE trial (n=718) to patients who got single-chamber transvenous pacemakers and were included in Truven Health MarketScan claims databases (n=1,436).

Cantillon and colleagues pointed out that the two arms of the study were subject to different definitions of procedural complications and that the transvenous pacemaker group did not have events adjudicated since they came from a database. Another limitation, they said, was the potential difference in operator experience between arms.

"It should be noted that the introduction of femoral vascular complications with [the] LCP represents a true trade-off created by the paradigm shift away from pectoral surgical incisional access to percutaneous femoral vascular access; the introduction of an 18-F vascular delivery sheath provides challenges to achieving hemostasis after use of femoral instrumentation," the authors noted. "However, the elimination of pocket-related and infection-related acute complications arguably more than compensates for the small increases in rates of vascular events in LCPs."

There were no incidents of tricuspid valve injury during Nanostim placement, Cantillon's group observed, but they said this is possible during device extraction.

For now, "this field is simply too young to judge and compare the long-term implications that remain, as of yet, unknown; indeed, the end-of-service clinical experience of the leadless device will not be fully understood for another 10-15 years," they estimated.

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