Subcutaneous ICD reduces rate of major lead-related complications: ATLAS
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Among patients who received implantable cardioverter defibrillator therapy, a subcutaneous vs. transvenous approach reduced major lead-related complications by 92% with no loss in device performance, according to data from the ATLAS trial.
ICDs are a cornerstone of therapy for people at high risk for ventricular arrythmias; however, they confer risk for periprocedural and late complications in up to 3% of recipients, most of which are related to the presence of the intracardiac lead, Jeff S. Healey, MD, FRCPC, professor in the division of cardiology at McMaster University in Hamilton, Ontario, said during a late-breaking clinical trial presentation at Heart Rhythm 2022.
As Healio previously reported, data from the PRAETORIAN trial demonstrated that the subcutaneous ICD (S-ICD; Emblem S-ICD System, Boston Scientific) was noninferior to the transvenous ICD (TV-ICD) in inappropriate shocks and complications, but more data from randomized controlled trials are needed to assess the differences in appropriate shock efficacy and inappropriate shocks, Healey said.
“S-ICD has been around for 10 years and in its current state, it is a suitable alternative to a transvenous device, particularly in patients where there is a desire to avoid lead-related complications,” Healey told Healio. “In properly selected and electrocardiographically screened patients, the S-ICD is a good alternative for a transvenous device.”
Assessing younger patients
For the ATLAS trial, researchers analyzed data from 503 adults aged 60 years or younger with either a standard indication for an ICD or an inherited arrythmia syndrome, prior pacemaker or ICD removal for infection, need for hemodialysis, prior heart valve surgery or chronic obstructive pulmonary disease. Patients were randomly assigned to S-ICD (n = 251) or TV-ICD (n = 252). All participants had a study ECG before the implant and at 6 months after implant. The mean age of patients was 49 years and 74% were men; many patients had inherited heart rhythm disorders, including 18.5% with hypertrophic cardiomyopathy and 16.7% with idiopathic ventricular fibrillation. About one-quarter of patients had a history of cardiac arrest and about one-tenth had a history of sustained ventricular tachycardia.
“This is a very different population than other trials we have seen in the past,” Healey told Healio.
The primary outcome was a composite of major perioperative, lead-related complications measured at 6 months after ICD implantation, including hemothorax or pneumothorax, cardiac perforations and lead dislodgement. A secondary 6-month safety composite outcome includes primary outcome events plus device-related infection, wound hematoma, MI, stroke or death. Mean follow-up was 2.5 years.
At 6 months, the rate of the composite primary outcome occurred in 4.8% of the TV-ICD group and 0.4% of S-ICD group, a 92% difference (OR = 0.08; 95% CI, 0-0.55; P = .003). There was a 22% reduction in risk for the composite safety outcome favoring S-ICD that was not statistically significant, with an HR of 0.78 (95% CI, 0.35-1.75).
“Likely, there is a distribution here on play of chance, given the relatively infrequent nature of these secondary adverse events,” Healey said.
The rate of inappropriate shocks was numerically higher for patients assigned the S-ICD vs. the TV-ICD, with rates of 2.7% and 1.2% per year, respectively (HR = 2.37; 95% CI, 0.98-5.77). In both groups, about 25% of all inappropriate shocks were because of electromagnetic interference due to the use of transcutaneous electrical nerve stimulation devices by patients, Healey said.
“Part of the story here is the reasons for inappropriate shock varied by device,” Healey said in an interview. “When the transvenous ICD shocked inappropriately, this tended to be due to atrial arrythmias, whereas with the subcutaneous ICD this tended to be due to T-wave oversensing.”
ICD effectiveness was similar in both arms, and there was a low rate of failed first appropriate shock. Ongoing follow-up will continue for several more years; however, early data for reoperation for ICD or lead-related issues showed a nonsignificant reduction of 22% favoring the S-ICD, Healey said.
“These data, in addition to the PRAETORIAN data [and] the long-term registries like UNTOUCHED, do give further reassurance that the [subcutaneous] ICD can be used as an alternative to transvenous device, particularly among individuals where lead-related complications are thought to be best avoided,” Healey told Healio.
Choice of device ‘a balancing act’
In discussion after the presentation, Christine M. Albert, MD, MPH, FHRS, chair of the department of cardiology and the Lee and Harold Kapelovitz Distinguished Chair in Cardiology at the Smidt Heart Institute at Cedars-Sinai, said ATLAS provides important data on a patient population that is often considered for an S-ICD.
“These are the kind of data that we need when we talk with our patients,” Albert said. “Now, we have two large trials, PRAETORIAN and ATLAS. How does ATLAS add to what we knew before? These are the patients who we are often thinking about putting in S-ICDs, because we want to avoid lead-related complications. These are younger patients who will have the device for a long time.”
ATLAS clearly showed a decrease in lead-related complications, though questions remain about long-term risks, Albert said, adding that the inappropriate shock rate, although not significantly different between devices, is something that should be followed longer term.
“It will always be a balancing act when we talk with our patients about which type of device to use,” Albert said.
Perspective
Back to TopKenneth A. Ellenbogen, MD
ATLAS was a very well-done study, and the data are in line with other clinical trials. It shows that the S-ICD appears to have a lower risk for acute complications; in particular, the rate of major lead-related complications was reduced by greater than 90% with the S-ICD. I am amazed they will be conducting long-term follow-up. Certainly, for lots of different patient groups, it should be our first-choice defibrillator.
There was a slightly higher risk for inappropriate shocks and different causes for the inappropriate shocks with the S-ICD compared with TV-ICDs. However, ATLAS was not like other trials where patients are randomized regardless of age or underlying disease. These are younger patients because there was a higher incidence of nonischemic cardiomyopathies, as well as genetic cardiomyopathies. The take-home message is that insurance companies should have no ability to refuse patients who need S-ICDs. There are clearly many for whom this is the ideal device.
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Healey J. Late Breaking Clinical Trials: Randomized Clinical Trials. Presented at: Heart Rhythm 2022; April 29-May 1, 2022; San Francisco (hybrid meeting).
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