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Leadless pacemaker effective, events low in first 300 patients
LONDON — A leadless pacemaker met prespecified sensing and pacing requirements in most patients, and was associated with device-related serious adverse events in approximately one in 15 patients, according to findings presented at the European Society of Cardiology Congress.
Vivek Y. Reddy, MD, presented results from the first 300 patients with need for permanent single-chamber ventricular pacing who were implanted with the 1-cc leadless pacemaker (Nanostim, St. Jude Medical) in the LEADLESS II study.
Vivek Y. Reddy
The primary efficacy endpoints were acceptable pacing threshold, defined as ≤ 2 V at 0.4 milliseconds, and acceptable sensing amplitude, defined as either R wave ≥ 5 or a value at 6 months that was greater than or equal to the value when the device was implanted. The primary safety endpoint was freedom from serious adverse events related to the device at 6 months.
Reddy, director of electrophysiology at Mount Sinai Hospital, New York, and colleagues presented 6-month results of the primary outcomes from the first 300 patients, and other results from the 526 patients that were enrolled as of June 2015.
They set, based on historical data, performance goals of 85% for the primary efficacy endpoint and 86% for the primary safety endpoint.
In the 526 patients who received the device as of June 2015, implantation was successful in 95.8%, Reddy said.
In an intention-to-treat analysis, Reddy and colleagues determined that 90% (95% CI, 86-93.2; P = .007) of patients met the primary efficacy endpoint and that 93.3% (95% CI, 89.9-95.9; P < .001) of patients met the primary efficacy endpoint.
The most common serious adverse events in the 6.7% of patients who had them were device dislodgement with percutaneous retrieval (1.7%), cardiac perforation (1.3%) and elevation of pacing threshold that required device removal and replacement (1.3%), according to the researchers.
“It is likely that the complication rate should improve with increased operator experience,” Reddy said at a press conference. “I want to underscore the fact that 99 out of 100 operators in this trial had never performed a leadless pacing implantation procedure. You see the full learning curve in this trial.”
An encouraging finding is that “based on the device use characteristic over these first 6 months, the battery longevity is estimated to be a mean of 15 years, with a range between 14.2 and 15.8 years,” Reddy said. – by Erik Swain and Katie Kalvaitis
References:
Reddy VY, et al. Hot Line II: Atrial Fibrillation/Pacing. Presented at: European Society of Cardiology Congress; Aug. 29-Sept. 2, 2015; London.
Reddy VY, et al. N Engl J Med. 2015;doi:10.1056/NEJMoa1507192.
Disclosures: The study was funded by St. Jude Medical. Reddy reports receiving grant support and personal fees from Biotronik, Boston Scientific, Medtronic and St. Jude Medical.
Perspective
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A leadless pacemaker is a disruptive technology that moves away from the conventional implant. Through the femoral approach, you implant a completely implantable miniaturized leadless pacemaker. The device gets implanted in the right ventricle and provides pacing back-up to the patients.
LEADLESS II looked at 526 patients who were implanted with the leadless pacemaker. But the researchers did a primary efficacy and a primary safety analysis only on the first 300 who had completed their 6-month follow-up. They found that they could implant the pacemaker in 96% of people safely. Primary efficacy was assessed by examiming the pacing threshold and R wave sensing, which was good in 90% of the patients. They found that 6.7% of patients had adverse events, including perforation of the heart, a migration of the device and changes in electrical parameters necessitating extraction and relocation of the device. Perforation and migration are the two big issues that people are concerned about. But the trial met its primary safety endpoint as well.
The data from this nonrandomized prospective multicenter trial were compared with the primary efficacy and safety endpoints from historical data, compared to which, it looked pretty good. The study shows that this is a safe and efficacious strategy. But it is only a single-chamber pacemaker strategy, so it can be only deployed in a certain subset of patients who are candidates for single-chamber pacemakers.
Now we have to see the long-term results. How long do these batteries last? Can these devices be extracted in the future after 5 years of being implanted when the body is growing tissue around it? If you need to implant a second one in somebody because the battery has run out, can you do that? Will this technology evolve to include atrial pacing? Will it be able to pace more than one chamber like the conventional pacemakers? In the future, what the technology really needs to evolve into is to have the same device diagnostic parameters, sensor strategies and remote monitoring capabilities that are present with conventional pacemakers. I think leadless pacemakers will eventually need to provide those features if they are to stand the test of time.