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A leadless cardiac pacemaker demonstrated ‘good safety and reliable function’ according to a study Hot Line session yesterday. The observational Leadless II trial, published simultaneously in the New England Journal of Medicine, suggests that the new device might serve as an alternative to conventional transvenous pacemakers.
‘These multicentre data represent the largest population of patients to receive a leadless pacemaker system and as such provide unique insight into their efficacy and safety,’ said Vivek Reddy from Icahn School of Medicine at Mount Sinai, New York.
Despite considerable technological advances since the introduction of conventional cardiac pacemakers more than 50 years ago, adverse events still occur in around one in 10 patients. These are typically related to the transvenous leads, surgical pocket, or pulse generator. Leads can be susceptible to dislodgement, fracture, or insulation failure and, said Reddy, can also cause infection, cardiac perforation, venous occlusion, and tricuspid regurgitation.
The fully self-contained leadless cardiac pacemaker investigated in this study - with combined battery, electronics and electrodes encapsulated into a small unit - has been designed to overcome such problems. Describing the device, Reddy said that it is 42 mm long, 6 mm wide, and was delivered to the right ventricle transfemorally using an 18F introducer/steerage catheter. The device is currently approved in Europe, but not the US.
In this Leadless II trial a first cohort of 300 patients was followed up for six months, while a second cohort included an additional 226 patients. The study took place in 56 centres in the US, Canada, and Australia.
Results showed that the primary endpoint (therapeutically acceptable pacing capture threshold and a therapeutically acceptable sensing amplitude) was achieved in 270 of the 300 primary cohort patients (90%). Reasons for failure included inadequate pacing capture threshold in four patients and inadequate sensed R-wave amplitudes in 16 patients. The primary safety end point was met in 280 of the 300 patients (93.3%), with cardiac perforation experienced by 1.3%, device dislodgement by 1.7%, elevated pacing thresholds necessitating device retrieval in 1.3% and vascular complications in 1.3%.
Of the 289 patients who had a successful implant followed out to six months 270 (93.4%) achieved adequate pacing and sensing threshold.
The rate of device-related serious adverse events was 6.5% among the treated subjects, including cardiac perforation in 1.5% of patients, device dislodgement in 1.1%, and device retrieval due to elevated pacing thresholds in 0.8%.
The device was shown to be retrievable in the seven patients who needed a replacement at a mean of 160 days after implantation. On the basis of the study, investigators estimated that battery longevity was 15 years. ‘It is likely that the complication rate should improve with increased operator experience,’ said Reddy, adding notably of 100 operators only one had prior experience of the implantation technique.
There will be important questions on how to manage the device after battery depletion, said Reddy. ‘We’ve shown you can remove the device up to a year, but the real question is what happens five to fifteen years down the line - whether we will be able to retrieve devices or abandon them.’
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