How Effective Are Implantable Cardioverter Defibrillators in Heart Failure?

MINNEAPOLIS—While improvement in left ventricular ejection fraction (EF) to greater than 35% occurs in many patients with reduced EF at baseline, it is not clear whether implantable cardioverter defibrillator (ICD) therapy improves survival for these patients.

A study published in JAMA Cardiology sought to examine the efficacy of ICD therapy in reducing risk of all-cause mortality and sudden cardiac death among patients with an EF at 35% or lower at baseline, regardless of whether they had an improvement to greater than 35% during follow-up.1

To do that, a study team led by researchers from the VA Healthcare System in Minneapolis and the University of Minnesota performed an analysis of data collected in the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT). That study randomly assigned 2,521 patients to placebo, amiodarone or ICD between 1997 and 2001.

During the 2016 analysis conducted between January and July, a subset of 1,902 participants (75.4%) of the SCD-HeFT had a repeated assessment of EF an average of 13.5 months after randomization and were stratified by EF less than or equal to 35% and greater than 35% based on the first repeated EF measurement after randomization. All-cause mortality was then compared in 649 patients randomized to placebo vs. 624 patients randomized to ICD. Follow-up started with the repeated EF assessment.

Results indicated that repeated EF was greater than 35% in 29.8% randomized to ICD and 28.5% randomized to placebo. In addition, during a median follow-up of 30 months, the all-cause mortality rate was lower in the ICD vs. placebo group, both in patients whose EF remained 35% or lower and in those whose EF improved to greater than 35%.

Compared with placebo, the adjusted hazard ratio for the effect of ICD on mortality was 0.64 (95% CI, 0.48-0.85) in patients with a repeated EF 35% or lower and 0.62 (95% CI, 0.29-1.30) in those with a repeated EF higher than 35%. No link was found between treatment assignment and repeated EF for predicting mortality.

“Among participants in the SCD-HeFT who had a repeated EF assessment during the course of follow-up, those who had an improvement in EF to >35% accrued a similar relative reduction in mortality with ICD therapy as those whose EF remained ≤35%,” study authors concluded. “Prospective randomized clinical trials are needed to test ICD efficacy in patients with an EF >35%.”

The researchers cautioned that the results should not be extrapolated to patients with an EF between 35% and 50% and who have never had an EF less than or equal to 35% in the past. “These patients may represent a different population than the one studied in this investigation and are the focus of an ongoing large prospective cohort study to identify risk markers of SCD,” they wrote.

  1. Adabag S, Patton KK, Buxton AE, Rector TS, Ensrud KE, Vakil K, Levy WC, Poole JE. Association of Implantable Cardioverter Defibrillators With Survival in Patients With and Without Improved Ejection Fraction: Secondary Analysis of the Sudden Cardiac Death in Heart Failure Trial. JAMA Cardiol. 2017 Jul1;2(7):767-774. doi: 10.1001/jamacardio.2017.1413. PubMed PMID: 28724134.

 

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