Leadless pacing has shown to be safe and feasible with the Nanostim (St Jude Medical), self-contained, single-chamber leadless cardiac pacemaker, according to the LEADLESS trial results, recently published in Circulation.
LEADLESS, a prospective, non-randomised, single-arm multicentre trial, is the first study exploring the implantation of a self-contained cardiac pacemaker in humans. The results of this study were first presented at the Heart Rhythm Association scientific sessions in 2013.
Although traditional pacemakers pose minimal risk, patients are still vulnerable to some short- or long-term complications, says Vivek Y Reddy, lead author of the study and director of the Cardiac Arrhythmia Service at Mount Sinai Hospital in New York, USA.
Those complications can stem from the pulse generator implanted under the skin of the chest, where infections or skin breakdown can occur, and particularly from the transvenous leads that can potentially break, dislodge or contribute to a vein blockage.
This new pacemaker has no leads-its pulse generator lies within the right ventricle of the heart-and is placed with a transcatheter procedure through the femoral vein, eliminating the need for surgery. It is indicated for patients who require single-chamber pacing. Patients who need dual-chamber pacing would still require traditional pacemakers, according to Reddy.
The study was conducted in 33 Caucasian patients, average age 77, two-thirds men, at two hospitals in Prague and one in Amsterdam. The authors report that most of the patients treated had permanent atrial fibrillation with atrioventricular (AV) block (n=22, 67%). There were also patients with normal sinus rhythm with second or third degree AV block and with a low level of physical activity or short expected lifespan (n=6, 18%), and patients with sinus bradycardia with infrequent pauses or unexplained syncope with electrophysiological findings (n=5, 15%).
The self-contained pacemaker was successfully implanted in 32 patients (97%). Ninety-four per cent were free of complications through the three-month study period, the researchers report. There was one patient who suffered complications during the procedure and underwent emergency surgery but later died after suffering a stroke.
The leadless pacemaker system also includes single- or triple-loop snare retrieval catheters that can retrieve the device once it is fully deployed. In this series of patients, the authors write “we were able to remove one device acutely from the left ventricle and one subacutely from the right ventricle, at five days.” However, they note, “The safety and efficacy of retrieving the device (acute and chronic), especially with regard to the potential complications associated with manipulation of large retrieval catheters/sheaths within the right ventricle, requires confirmation.”
After three months, the new pacemakers were functioning well, the researchers found. They are continuing to track the patients and expect to report longer-term outcomes later this year. Meanwhile, a much larger study at multiple US locations that will include longer-term follow-up is under way, Reddy says. “Overall, the self-contained pacemaker is a paradigm shift in cardiac pacing,” he adds.
Nanostim, the maker of the leadless pacemaker, funded the study.