In a contemporary population of heart failure with reduced ejection fraction (HFrEF), ICDs for primary prevention were found to reduce short- and long-term mortality, but only a small fraction of eligible patients received them. The findings from the SwedeHF Registry were presented Sept. 3 at ESC Congress 2019 and published in Circulation.

"Most randomized trials on ICD use for primary prevention of sudden cardiac death in HFrEF enrolled patients more than 20 years ago," said principal investigator Benedikt Schrage, MD. "However, characteristics and management of HFrEF have substantially changed since then and it is not known whether ICD improves outcomes on top of contemporary treatments." He also noted that whether all subgroups benefit equally from an ICD is unclear.

Of 16,702 eligible patients in SwedeHF registered between May 11, 2000 and Dec. 31, 2016, only 1,599 (9.6 percent) had an ICD. Their mean age was 73 years and most (73 percent) were men. The propensity-matched study population consisted of 1,296 patients with an ICD and 1,296 patients without an ICD.

Patients who received an ICD were younger, more likely to be men and to receive guideline-directed medical therapy for HF. They were also more likely to have a history of ischemic heart disease, lower ejection fraction and a longer duration of HF, but less likely to have other comorbidities.

Results showed over a median follow-up of 2.69 years, there were 985 deaths (37.7 percent) in the matched cohort. For the endpoint of all-cause mortality, the risk of death was 12.7 percent and 16.9 percent in the ICD and non-ICD recipients, for an absolute risk reduction at one year of 4.2 percent (hazard ratio [HR], 0.73; p<0.01). At five years, the absolute risk reduction was 2.1 percent (HR, 0.88; p=0.04).

At one year, there were 737 cardiovascular deaths (28.2 percent). The one-year risk for cardiovascular mortality was 10.1 percent and 13.9 percent in the ICD ad non-ICD recipients, respectively, for an absolute risk reduction of 3.8 percent (p<0.01). At five years, this risk was 36.6 percent and 39.5 percent (HR, 0.88).

The short-term and long-term mortality benefit was consistent across subgroups, including patients with or without ischemic heart disease, men and women, patients younger and older than 75 years, those enrolled earlier vs. later in SwedeHF and thus receiving less or more contemporary treatment, and for patients with or without CRT.

"Our findings support the current recommendations and call for better implementation of ICD use in clinical practice," concluded Schrage.

In an accompanying editorial, Sana M. Al-Khatib, MD, MHS, FACC, and Fred M. Kusumoto, MD, FACC, comment that "the small number of patients who received an ICD may have magnified the apparent benefit of ICD due to unidentified covariates associated with risk of SCD; however, the authors used rigorous statistical methods including propensity score matching, and the results of the negative control analysis lend credibility to their findings."

While noting that the subgroups were too small for sufficient statistical power for robust comparisons, among other caveats, Al-Khatib and Kusumoto concluded the study "adds to the mounting evidence that ICDs are associated with improved survival in contemporary patients with HFrEF and highlights the need for strategies to improve their utilization."

Clinical Topics: Arrhythmias and Clinical EP, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias

Keywords: ESC 19, ESC Congress, Defibrillators, Implantable, Primary Prevention, Death, Sudden, Cardiac

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