The Nanostim implantable pacemaker made by St. Jude Medical (NYSE:STJ) met its 6-month safety and efficacy endpoints, according to data presented over the weekend at the annual meeting of the European Society of Cardiology in London and published in the New England Journal of Medicine.
The Leadless II study enrolled 526 patients in the primary cohort, with 300 completing the 6-month protocol in June. The entire group was followed for a mean 6.9 months, showing successful implantation of the Nanostim device in 504 (95.8%) of subjects, according to the NEJM paper. In some 29.8% of the cases, the Nanostim device needed repositioning; in 22 cases (4.4%) the device needed repositioning more than twice.
“In summary, the Nanostim leadless cardiac pacemaker met pre-specified pacing and sensing requirements in 90% of the patients in whom an implantation was attempted and in 93.4% of the patients in whom the implantation was successful,” the researchers wrote, noting that the study design was limited in not allowing a direct comparison to conventional pacers.
“Currently, the leadless cardiac pacemaker can serve as only a single-chamber ventricular pacemaker, which accounts for a minority of implanted pacemakers in the United States. The leadless cardiac pacemaker also cannot provide electrographic data. Refinements in device-to-device communication, atrial affixation, and device diagnostics would be necessary for this device to fully replace conventional dual-chamber pacemakers,” they wrote.
“Leadless pacing is a new frontier for modern medicine, and a potential solution for physicians who want to retain the reliability of conventional pacing options but offer their patients a less invasive procedure,” chief medical officer Dr. Mark Carlson said in prepared remarks. “The Nanostim leadless pacemaker allows for a procedure without the need for a surgical pocket or the leads required by traditional pacemakers. Combined with prior data from the Leadless trial, the results of Leadless II demonstrate the Nanostim leadless pacemaker should be considered as a clinical alternative by physicians who want to provide patients a leadless pacing option that offers long-term longevity and device retrievability.”
The researchers said 270 patients (90.0%; 2-sided 95% confidence interval [CI], 86.0 to 93.2) reached the primary efficacy end point in an intention-to-treat analysis. Device implantation was unsuccessful in 11 patients; among the remaining 289 patients in whom implantation was successful, 270 reached the primary efficacy end point (93.4%; two-sided 95% CI, 89.9 to 96.0; P<0.001), according to the study.
Nanostim met the primary safety endpoint in 280 of 300 patients (93.3%; 2-sided 95% CI, 89.9 to 95.9), with 22 device-related serious adverse events in 20 patients (6.7%) over a period of 6 months. The rate of device-related serious adverse events was 6.7%, including device dislodgement in 1.7% of patients, cardiac perforation in 1.3%, elevated pacing thresholds requiring device retrieval and reimplantation in 1.3%, and vascular complications in 1.3%.
That compares with a 3.2% complication rate with conventional ventricular pacemakers, excluding lead fracture but including pneumothorax in 1.1%, lead dislodgement in 0.8%, and infection in 0.5%, the researchers wrote.
Importantly for St. Jude, which earlier this year paused enrollment in a European Nanostim trial to evaluate a series of adverse events including cardiac perforation and dislodgement, the rate of cardiac perforation (1.5% among the 526 patients in the total cohort) was similar to the rate observed with transvenous leads, they wrote. Enrollment in the Nanostim was paused once before, in April 2014, after researchers reported 6 instances of perforation, including 2 patient deaths, out of more than 200 implantations.
For the entire 526-patient cohort the rate of device-related serious adverse events was 6.5%, according to the NEJM study, including cardiac perforation in 1.5%, device dislodgement in 1.1% and device retrieval due to elevated pacing thresholds in 0.8%. There were 28 deaths (5.3%) during follow-up of the larger group, with 19 deaths (68%) occurring within 6 months, 8 (29%) between 6 and 12 months, and 1 (4%) after 12 months.
St. Jude acquired Nanostim in 2013 for $123.5 million, 2 years after making a strategic investment in the Milpitas, Calif.-based company.