BOSTON—All 140 patients analyzed and enrolled in a single-arm, multicenter trial had successful implants with the Micra Transcatheter Pacing System (TPS), a miniaturized leadless pacemaker that is not yet approved in the U.S. The mean implant time was 37 minutes.

After a mean follow-up of 1.9 months, all but one of the patients were alive and remained in the study. The one death was unrelated to the procedure.

Serious adverse events occurred in 5.7 percent of patients, and two patients required hospitalization.

This analysis was the first of three prespecified analyses and occurred after the first 60 patients passed their three-month follow-up.

Lead researcher Philippe Ritter, MD, of Hopital Haut-Leveque in Pessac, France, said there were no unforeseen events, no device telemetry issues, no dislodgements, no infections or no repoperations.

Ritter presented the results on May 15 in a late-breaking clinical trials session at Heart Rhythm 2015. He said this study was the first in-human experience of a miniaturized leadless pacemaker.

“I’ve been involved in pacing now for 30 years, and I’ve never seen such results,” Ritter said.

In April 2015, the Micra TPS was awarded a CE mark in Europe. The FDA has not approved the device.

The Micra TPS’s volume is 93 percent less than a conventional system, while its mass is 10 times less. The battery service life of the Micra TPS (Medtronic) is 9.6 years compared with 10.3 years for a conventional system.

During a news conference, Ritter was asked if the Micra TPS device would be his preferred device in these patients.

“Definitely, yes,” he said. “We are very enthusiastic, all the investigators. Why? Because we were expecting that the enrollment would be over by next October, when it’s already done. It proves that patients are enthusiastic because they accept it very well.”

The 140 patients in this analysis underwent implants at 23 centers in the U.S., Europe and Asia Pacific. At baseline, the mean age was 78, and 61 percent of the patients were males. There was a wide range in age (21 to 94) and weight (41 kg to 148 kg). In addition, 65 percent of patients had bradycardia with permanent or persistent atrial tachycardia or atrial fibrillation.

All catheters used in the study were heparinized, but the anticoagulation was at the physicians’ discretion. Ritter said 44 percent of patients were on anticoagulants and 29 percent received antiplatelets. Forty percent of patients received heparin intravenously.

During the implant, 59 percent of the procedures were successful after one deployment, 81 percent were successful within two deployments and 96 percent were successful within four deployments.

There were nine serious adverse events in eight patients: five were dysrhythmias, three were cardiac complications and one was an arterial pseudoaneurysm.

Ritter said two other analyses are scheduled: the primary objective analysis will occur after the first 300 patients passed their three-month follow-up, while a long-term performance analysis is planned for after the first 700 patients are followed for 12 months.

The study’s enrollment was completed earlier this month, which was six months ahead of its deadline, according to Ritter.