Subcutaneous ICD noninferior to transvenous ICD for primary, secondary prevention
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A subcutaneous implantable cardioverter defibrillator was noninferior to a transvenous ICD regarding major ICD-related adverse events in patients indicated for such treatment, according to data from the PRAETORIAN trial presented at the virtual Heart Rhythm Society Annual Scientific Sessions.
Patients indicated for ICD
Researchers analyzed data from 849 patients from 39 centers in the United States and Europe with a class I or IIa indication for ICD therapy for primary or secondary prevention. Patients were assigned subcutaneous ICD (Emblem S-ICD System, Boston Scientific; n = 426; median age, 63 years; 21% women) or transvenous ICD (n = 423; median age, 64 years; 18% women).
“The [subcutaneous] ICD was introduced already 12 years ago to overcome lead issues with transvenous ICDs,” Reinoud E. Knops, MD, PhD, cardiac electrophysiologist at Academic Medical Center in Amsterdam, said during the press conference. “However, not having a lead in the heart makes sensing of the heart rhythm difficult. That might lead to more inappropriate shocks, so that might be a negative aspect of the [subcutaneous] ICD.”
The primary endpoint was ICD-related complications and inappropriate shocks, which was assessed for a median of 48 months.
“The important part of this study is that since the inappropriate shocks are part of the composite endpoint, it’s obviously important that programming in this study is similar, so programming of ICDs in the [subcutaneous] ICD group and transvenous ICD groups are similar,” Knops said during the presentation.
Knops also said long follow-up time is important. During the press conference, he said: “The main results, we waited quite a long time. We’ve been working on this study for almost 10 years, quite some time, because we felt that to really look at complications of ICD therapy, you have to wait a while. It takes time, for instance, lead complications to develop, so that’s why we had a minimum of 4 years of follow-up.”
The primary composite endpoint occurred in 15.7% of patients in the transvenous ICD group and 15.1% in the subcutaneous ICD group.
“Since this was a noninferiority design in the study, the initial results of this study show that with regard to primary composite endpoint, the [subcutaneous] ICD is noninferior to the transvenous ICDs,” Knops said during the press conference.
Individual endpoint components
Researchers also assessed individual components of the primary endpoint. Inappropriate shocks occurred in 9.7% of patients assigned subcutaneous ICD vs. 7.3% of those assigned transvenous ICD (HR = 1.43; 95% CI, 0.89-2.3). Device-related complications were observed in 9.8% of patients in the transvenous ICD group and 5.9% of those in the subcutaneous ICD group (HR = 0.69; 95% CI, 0.44-1.09).
Assessment of individual components of device-related complications between the subcutaneous ICD group and transvenous ICD showed differences, including the occurrence of infection (4 vs. 8, respectively), bleeding (8 vs. 2, respectively) and thrombotic event (1 vs. 2, respectively).
“I think that helps physician-guided choices when you have to select the proper device for the proper patient,” Knops said during the presentation.
When assessing lead-related complications, more events occurred in the transvenous ICD group vs. the subcutaneous ICD group (6.6% vs. 1.4%; HR = 0.24; 95% CI, 0.1-0.54).
There was no difference in all-cause mortality in patients assigned subcutaneous ICD and transvenous ICD (16.4% vs. 13.1%, respectively; P = .2).
“The main conclusion is that the [subcutaneous] ICD should be considered in all patients in need of an ICD that do not have a pacing indication,” Knops said during the press conference.
Knops said final results of the PRAETORIAN trial were accepted for publication in The New England Journal of Medicine. – by Darlene Dobkowski
Reference:
Knops RE, et al. LBCT01-02. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 6-9, 2020 (virtual meeting).
Disclosure: Knops reports he received consultant fees and research grants from Abbott, Boston Scientific, Cairdac and Medtronic and has stock options from AtaCor Medical.
Perspective
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Andrew D. Krahn, MD, FHRS
The technology of subcutaneous ICD is about 10 years old and has much less of a robust track record than the transvenous ICD does. As a result, there is enthusiasm about the concept of changing the nature of the technology that can serve a certain patient population. The real question was how broadly useful it is and how it compares to the older technology. As a result, there are varying degrees of adoption based on enthusiasm about the technology, but not a lot of evidence other than case series, and no good comparative evidence in a randomized trial.
The community has been looking forward to a comparative study such as this. There is a second trial near completion called ATLAS that is coming soon, and the lead investigator is Jeff S. Healey, MD. That will be a second randomized dataset.
PRAETORIAN was designed as a noninferiority trial. The main reason for that was because the assertion was not that the device was necessarily superior; they both have strengths and weaknesses. We have been discussing this with patients since the introduction of the technology.
The key takeaway point is that the device was as effective and safe as a transvenous ICD. The limiting factor with the subcutaneous ICD is the absence of antitachycardia pacing. In the early data, there was concern about incidence of inappropriate shocks. The key thing that happened with PRAETORIAN was that the investigators were systematic about both the programing of the patients for shocks as well as the nature of the arrhythmias.
There are still more data to come; the peer review process has not yet presented itself. The authors are to be commended that the paper is in press in The New England Journal of Medicine. As a result, the overarching data suggest the inappropriate shock rate was a little bit higher, but not enough that it was clinically substantive, and the absence of anti-tachycardia pacing did not appear to disadvantage patients in terms of the overall shock burden.
The corollary of this is we have known for years that a transvenous lead system has its limitations from the standpoint of a surgical implant, the complications around lead performance, etc. If anything, the surgical complications and short-term complication rates were comparable or a little higher with the transvenous system. This suggests that if there is an expert implant team on both sides of the technology, the use of either technology is supported. Arguably, in the right hands, the subcutaneous ICD may end up being a more durable technology.
The average follow-up in this trial is long enough to capture most of the things that reflect the implant. What is not there that we still want to see in the extension study is what happens over time because we know, for example, transvenous leads have durability issues as their Achilles’ heel.
With any kind of change management, there’s an early adopter group of people who are enthusiastic about the subcutaneous ICD. The degree of uptake in the global community has been modest because it has been more targeted at patients who are intuitively going to benefit. The real question in this situation is now that the device has shown equivalence, will the uptake in a more general ICD population be greater? That also speaks to the UNTOUCHED trial, and it argues that you can go into a conversation with a patient about the surgical procedure and be open minded to either technology based on the details of clinical judgment and patient preference.
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Knops RE, et al. LBCT01-02. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 6-9, 2020 (virtual meeting).
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