One of the longest and longest follow-ups of patients implanted with subcutaneous lead implantable cardioverter defibrillator (S-ICD), now marketed as EMBLEM S-ICD (Boston Scientific), draws a solid performance chart that has certainly improved over the years.
The S-ICD has maintained its reputation as a niche device after more than a decade on the market, probably in large part due to its limited capabilities compared to the more complete implantable cardioverter defibrillators (ICDs). transvenous derivations, which remain the main gold standard.
But the experience and design and software upgrades over the years can have decreased the clinical impact of some of these limitations of S-ICD, which include lack of antitacycardic rhythm (ATP) and, at least in previous years, the propensity to t-wave suppression, the researchers say. Both issues can favor shocks that could be avoided with most conventional ICDs. The device also lacks a chronic bradycardia rate, which rules out its use in many patients with indication for CIM.
However, the prevalence of shocks is adequate, that is, for potentially fatal ventricular tachycardia or fibrillation (VT / VF): was about 16%, in this “final report” of the WITHOUT EFFORT Study of the European S-ICD register after the market. Approximately half of the prevalence of almost 17% of inadequate shocks over 5 years was seen in the first 12 months after implantation.
On the other hand, cardioversion was successful in 98% of cases, and the first shock in 90%, Pier D. Lambiase, PhD, reported on April 24 to European Heart Rhythm Association (EHRA) 2021 congresses.
“Only” 2% of the cohort switched from S-ICD implanted to transvenous systems to leverage their bradycardia rate capacity in four patients, ATP in seven patients, or cardiac resynchronization therapy (CRT) in nine patients, he said.
S-ICD was approved in Europe in 2008 and by the US Food and Drug Administration (FDA) in 2012. Patients with EFFORTLESS implanted the device from 2011 to 2014.
Although a suspected case of lead failure was investigated and ruled out, “Interestingly, there were no definitive electrode failures in this population of nearly 1,000 patients,” said Lambiase, University College London, UK.
This observation may have referred to the recent one defined by the FDA Class I remember of electrode components due to a potential risk of fractures. The devices involved had been manufactured from March 2016 to November 2020. It was the first of two S-ICD Security reminds the United States that it will be released in the last 6 months.
The rate of shocks delivered improperly in response to atrial fibrillation (AF) o supraventricular tachycardia, another perceived drawback of S-ICD which is also a potential problem with transvenous lead systems, was “low,” around 3%, Lambiase said.
EFFORTLESS, conducted at 43 European centers, followed 984 patients for an average of 5.1 years and a mean duration of S-ICD use of 4.4 years; their initial average age was 48 years and the average ejection fraction was 43%. The etiologies of patients ’heart failure were ischemic in 29%; the rest had various non-ischemic conditions, including hypertrophic cardiomyopathy and an assortment of canalopathies. The indication of CIM was of primary prevention in 65%.
Inadequate shocks delivered by the S-ICD in recent years of follow-up correlated with the previous development of detected but not impacted monomorphic TV, which self-terminated, Lambiase noted. These accounted for 45% of the detected episodes of monomorphic TV, the type of TV that best responds to ATP.
“This is important because it means that if we can identify these inappropriate episodes early, it is possible to reprogram the device and prevent these shocks from occurring,” he said.
Inadequate complications and shocks in EFFORT
|End points||1 year (%)||5 years (%)|
|Overall complication rate||
|Inadequate shocks for t> wave overvoltage||3.4||5.8|
A history of valve surgery, compared to this surgery, was the most potent measured predictor of late complications or inadequate shock, with a risk ratio (HR) of 5.77 (95% confidence interval). [CI], 2.22 – 15.03; Pg = .0003) in multivariate analysis. A history of cardiac arrest nearly tripled the risk, HR, 2.70 (95% CI: 1.24 – 5.91; Pg = .013).
Performing a cardioversion test within 30 days of S-ICD implantation and the presence of AF reduced the risk of complications or inappropriate shock by three-quarters (Pg = .017 i Pg = 0.034, respectively), Lambiase reported.
There were 91 deaths (9.2%) in the study, but none were related to the S-ICD system or implantation procedure, he said. Approximately 40% of deaths were non-cardiac, 38% were cardiac but not arrhythmic, and three (0.3%) were arrhythmic, although another 11% of deaths were of unknown cause.
“A worthy compensation”
“The EFFORTLESS study demonstrated efficacy comparable to studies with transvenous ICDs, avoiding the serious complications associated with transvenous referrals,” said Giovanni Luca Botto, MD, ASST Rhodense-Garbagnate Milanese Hospital, Italy, as a guest speaker for the presentation of Lambiase.
Few patients experienced more than one episode of monomorphic TV during the five years, he observed, and nearly half self-interrupted while the rest caused shocks. Therefore, the need for ATP in the study was only 0.4% per year in the cohort which, by design, did not show the need to agree at the time of S-ICD implementation.
“I firmly believe that patients as well as doctors could accept that unique or infrequent episode of an ICD shock for TV that may be susceptible to ATP” from an S-ICD, Botto said, “as a worthy commitment to avoid long-term lead complications of a transvenous CDI “.
Still, the lack of pace is probably largely behind the “lower-than-expected” adoption of S-ICD in practice, he noted.
“Not all patients need rhythm, but I think the vast majority of patients benefit from the ATP that subcutaneous MIC does not provide at this stage,” said Haran Burri, MD, University Hospital of Geneva, Switzerland, in a round table during EHRA sessions.
There is a site for S-ICD, “and I’m an S-ICD user,” he said. But this use depends on the proper selection, no doubt narrow, of the patient. “I see benefits with patients at high risk of infection, vascular access problems and very young patients with non-arrhythmias [amenable] at ATP “, for example.
“However, I think this therapy really needs to improve. We are really in the early stages,” he said. The S-ICD has “very limited programming capabilities” and “inappropriate shock rates are still a bit high, although they improve.”
Certainly, “transvenous MIC is necessary for patients who need a bradycardia rhythm,” Liesbeth Timmers, MD, Ghent University Hospital, Belgium, noted at the same forum. And “you also need a transvenous system” for the CRT.
But, “I think S-ICD should be considered in all patients who do not need stimulation,” as it avoids “lead complications and systemic infections” which are the main complications associated with transvenous derivatives, he said. dir Timmers.
Ironically, Botto sees a theoretically higher risk of lead and subcutaneous lead-associated infections with S-ICD as a “major” disadvantage. An often cited limitation of the device is its shorter projected service life compared to transvenous lead systems: perhaps 7 years versus 10 or more years.
“The lower longevity of the subcutaneous CIM compared to the transvenous one will result in a greater number of device replacements in the long run.” And these procedures themselves, Botto noted, are “loaded with an increased risk of infection.”
In light of the estimated seven-year life of the S-ICD generator, Lambiase said, “I think we’ll have to wait at least another five years to start seeing the impact of the generator changes. We’ve only had one infection. with a change of generator, of about 50 devices so far, in the cohort. But we will have to see the long-term results, really, in terms of the risk of infection. “
Multivariate predictions of effortless death
|End points||HR (95% CI)||Pg Value|
|BT expulsion fraction (in increments of 5 points)||0.78 (0.70 – 0.88||
|Kidney disease (against head)||5.87 (3.55 – 9.69)||<.0001|
|Diabetes (against head)||2.27 (1.37 – 3.76)||.0015|
|Age at implantation (in increments of 5 years)||1.14 (1.03 – 1.25)||.0088|
|Shock of any kind (no shocks)||1.71 (1.05 – 2.77)||.031|
|It is not significantly associated with mortality: defibrillation threshold tests, complications, primary vs. secondary prevention.|
Lambiase revealed the receipt of fees for speaking or serving on an advisory board of Boston Scientific, Abbott and Medtronic, and receiving educational and research grants from all three companies.
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