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Association Between Prophylactic Implantable Cardioverter-Defibrillators and Survival in Patients With Left Ventricular Ejection Fraction Between 30% and 35%
Study Questions:
What is the survival rate of systolic heart failure (HF) patients (left ventricular ejection fraction [LVEF] 30-35%) with and without implantable cardioverter-defibrillators (ICDs)?
Methods:
The study investigators conducted a retrospective cohort study of Medicare beneficiaries in the National Cardiovascular Data Registry (NCDR) ICD registry (January 1, 2006, through December 31, 2007) with an LVEF between 30% and 35% who received an ICD during a HF hospitalization, and similar patients in the Get With The Guidelines–Heart Failure (GWTG-HF) database (January 1, 2005, through December 31, 2009) with no ICD. They repeated the analysis in HF patients with an LVEF <30%. The statistical analysis was conducted on 3,120 patients with an LVEF between 30% and 35% (816 in matched cohorts) and 4,578 with an LVEF <30% (2,176 in matched cohorts). They applied propensity-score matching and Cox models. The primary outcome was all-cause mortality obtained from Medicare claims through December 31, 2011.
Results:
The study investigators found no significant differences in the baseline characteristics of the matched groups (n = 408 for both groups). In patients with an LVEF between 30% and 35%, there were 248 deaths in the ICD Registry group, within a median follow-up of 4.4 years (interquartile range, 2.7-4.9) and 249 deaths in the GWTG-HF group, within a median follow-up of 2.9 years (interquartile range, 2.1-4.4). The risk of all-cause mortality in patients with an LVEF between 30% and 35% and an ICD was significantly lower than that in matched patients without an ICD (3-year mortality rates: 51.4% vs. 55.0%; hazard ratio, 0.83 [95% CI, 0.69-0.99]; p = 0.04). Presence of an ICD also was associated with better survival in patients with an LVEF <30% (3-year mortality rates: 45.0% vs. 57.6%; 634 and 660 total deaths; hazard ratio, 0.72 [95% CI, 0.65-0.81]; p < 0.001) (p = 0.20 for interaction).
Conclusions:
The authors concluded that in systolic HF patients with an LVEF between 30% and 35% and <30%, survival at 3 years was better in patients who received a prophylactic ICD than in comparable patients with no ICD.
Perspective:
In most of the randomized clinical trials reporting the benefits of an ICD in systolic HF, the median LVEF is <30%. The findings of this study are important because it demonstrates the benefits of ICD implantation in those with an LVEF between 30-35%, particularly because it is an assessment of patients in the ‘real-world’ setting. These findings support the recommendations of the American College of Cardiology/American Heart Association guidelines on utilization of an ICD in HF patients. The next step would be to determine whether this survival benefit is also associated with improved quality of life, and whether indeed this is a cost-effective approach.
Keywords: Registries, Research Design, Follow-Up Studies, Proportional Hazards Models, Quality of Life, Research Personnel, Heart Failure, Stroke Volume, Medicare, Defibrillators, Implantable
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