BARCELONA — The first global experience having an extravascular implantable cardioverter-defibrillator (ICD) saw it working safely to avoid sudden cardiac deaths, albeit amid an excessive amount of inappropriate shocks, the EV ICD pivotal study showed.
People receiving the ICD for primary or secondary prevention experienced successful defibrillation in 98.7% out of 316 implantation attempts, the low limit of the confidence interval allowing these devices to meet up its 88% performance goal in detecting and terminating induced ventricular arrhythmias.
Freedom from major system- or procedure-related complications was 92.6% at six months, and these devices also met the safety goal of 79%, reported Ian Crozier, MB, ChB, of Christchurch Hospital in New Zealand, at the European Society of Cardiology (ESC) meeting. The outcomes were published simultaneously in the New England Journal of Medicine.
The extravascular ICD includes a single lead implanted substernally in a way that these devices can deliver pause-prevention pacing and antitachycardia pacing without the leads in the veins or heart, unlike the traditional transvenous ICD. The extravascular device can be smaller than subcutaneous ICDs and delivers shocks at about 50 % the power.
“Despite concerns or the impression that may be a dangerous procedure,” there is no cardiac injury during implant, no deaths from the task, no unique complications not already seen with transvenous and subcutaneous ICDs, in accordance with Crozier.
There have been no observed cases of mediastinitis, sepsis, or endocarditis linked to the extravascular ICD. However, there have been four extravascular ICDs which were explanted because of infection over follow-up averaging 10.six months, suggesting a risk much like what has been seen in subcutaneous ICDs.
Also, there have been 29 individuals who received 118 inappropriate shocks for 81 arrhythmic episodes. “The frequency of inappropriate shock of 8.5% at six months exceeds that of current ICDs but is comparable to that of early-generation transvenous and subcutaneous systems,” the authors noted.
Their observation that P-wave oversensing was to be blamed for most of the inappropriate shocks in the analysis cohort has resulted in new ICD programming recommendations and the ongoing development of a particular P-wave algorithm to lessen these events, Crozier stated.
Through the Q&Some of the presentation, ESC attendee Maged William, PhD, of Gosford Private Hospital in North Gosford, Australia, raised the question of extracardiac stimulation and potential discomfort for patients.
Crozier acknowledged that there is patient knowing of pacing, which varied from mild to moderate with “a small number of patients” experiencing greater sensations. The amount of people disabled due to discomfort reached 5%, he said.
EV ICD was a follow-up to a 2019 pilot study that had reported short-term device safety and efficacy.
Crozier and colleagues conducted today’s study at 46 participating sites in 17 countries with 356 people who have a class I or IIa indication for a primary or secondary prevention ICD. Exclusion criteria included a chronic pacing indication including cardiac resynchronization therapy.
Of these enrolled, 316 ultimately proceeded having an implantation attempt, that was performed by several dozen expert implanters.
Mean age was 53.8, and 25.3% were women. Approximately four out of five people got the extravascular ICD for primary prevention. Nearly half the cohort had ischemic cardiovascular disease.
Crozier reported that 302 device recipients completed the defibrillation testing protocol and were counted in the primary efficacy analysis.
The antitachycardia pacing of the extravascular ICD, as assessed with generalized estimating equations, was 50.8% successful in terminating spontaneous arrhythmia episodes.
No major intraprocedural complications were reported. By six months, the rate of major complications reached 7.3%.
There is one patient with a tool software issue that required device replacement. The program was revised and the issue didn’t resurface in other patients.
There have been two late lead fractures, one at 7 months and another at 11 months, related to implantation below the xiphisternum and substantial unanticipated bending conditions. The analysis sponsor responded by changing the implantation guidance.
“Implantation of the extravascular ICD requires accessing the substernal space, an anatomical location not traditionally approached by cardiologists,” Crozier and colleagues wrote. “Inside our study, which involved a separate training curriculum and initial collaboration with a cardiac surgeon, implantation procedures were performed safely in electrophysiology laboratories, which supports both importance of a thorough training curriculum and the generalizability of the practice.”
The investigators acknowledged that there is no comparison group receiving transvenous and subcutaneous ICDs in the analysis. In addition they cautioned that the relatively young patient population may limit the generalizability of the study’s leads to older, sicker patients.
The analysis was supported by Medtronic.
Crozier disclosed support from, and a relationship with, Medtronic.