BOSTON — A self-contained miniaturized leadless transcatheter pacing system was implanted safely and performed as expected in its first study in humans, researchers reported at the Heart Rhythm Society Annual Scientific Sessions.
The device (Micra, Medtronic) is less than one-tenth the size of conventional pacemakers and is about the size of a large pill. Rather than having leads, it attaches directly to the heart and delivers electrical impulses through an electrode.
Phillippe Ritter, MD, from Hôpital Haut-Lévêque, Pessac, France, reported data from the first 140 patients (mean age, 78 years; 61% men) with follow-up of at least 1 month.
Patients with Class I or II indications for VVI pacing underwent implantation of the device via the femoral vein; it was fixated in the right ventricle using four protractible nitinol tines, Ritter said at a press conference. Among the first 140 patients, most were indicated for the device because of bradycardia with permanent/persistent atrial tachycardia or atrial fibrillation (65%), sinus node dysfunction (15.7%) or atrioventricular block (13.6%).
Outcomes of interest were serious adverse events related to the device, and electrical parameters and function of the device. Mean follow-up was 1.9 months.
The implant was successful in 100% of patients. Mean implant time was 37 minutes and median number of deployments was one, Ritter said.
The rate of serious adverse events was 5.7%, which is comparable to a rate of 7.3% in a Medtronic reference dataset, Ritter said. There were no unforeseen events, device telemetry issues, dislodgements, infections, reoperations or related deaths. “These are tremendous complications with traditional devices and can lead to reoperations,” he said.
One patient died from a non-CV cause 139 days after implant, he said.
Ritter said eight patients experienced nine serious adverse events related to the device or the procedure, and three of the events resulted in hospitalization. There were five cases of transient dysrhythmia and one case of pericarditis, likely caused by mechanical stimulation from the catheter, and all were quickly managed and resolved, he said.
One patient had a pericardial effusion without tamponade after persistent repositionings of the device; the problem was resolved with drainage, but the patient had an acute MI 3 days later, Ritter said. Another patient had an arterial pseudoaneurysm requiring hospitalization.
Electrical measurements, including pacing capture threshold at 0.24 ms and R-wave sensing amplitude, were within expected range for all patients at implant, at prehospital discharge and at 1 month, Ritter said.
When the researchers examined 24-hour ambulatory surface ECG and device electrogram, they found expected sensing and pacing performance and no pauses due to inappropriate device operation.
“I’ve been involved in pacing for 30 years, and I’ve never seen such results,” Ritter said during the press conference. “The system is able to analyze quite properly the signals it receives in order to know when the system has to pace or not. It paces with a very low level of energy, less than 1 V for a short time of pulse width, which helps the patient remain stable.”
The device is not yet approved for sale in the United States, but received a CE Mark in April. – by Erik Swain
Ritter P, et al. Abstract LBCT02-01. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 13-16, 2015; Boston.
Disclosure: The study was funded by Medtronic. Ritter reports receiving consultant fees/honoraria from Medtronic Bakken Research Center.