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Who Benefits the Most From ICDs? | Journal Scan
Study Questions:
Which patients are likely to benefit the most from implantable cardioverter-defibrillator (ICD) implantation over an extended time period?
Methods:
Data from 13 randomized ICD trials (ICD vs. no ICD) were pooled, and comprised 8,910 patients, of whom 2,194 died during follow-up. Noncardiac risk of death was estimated using a Gompertz–Makeham function, which adjusts for increasing “competing” risk from aging and comorbidities. Lifespan-gain was extrapolated to a time-horizon of >20 years.
Results:
At 3 years, directly observed lifespan-gain was strongly dependent on baseline event rate (r = 0.94, p < 0.001). However, projecting beyond the duration of the trial, lifespan-gain increased rapidly and nonlinearly with time. At 3 years, lifespan gain averaged 1.7 months, but by 10 years, up to ninefold more. Lifespan-gain over time horizons >20 years was greatest in lower-risk patients (~5 life-years for 5% baseline mortality, ~2 life-years for 15% baseline mortality).
Conclusions:
The authors concluded that while high-risk patients may have the greatest short-term gain, the growth of lifespan over time means that it is the lower-risk patients (e.g., primary prevention ICD implantation) who gain the most life-years over their lifetime.
Perspective:
Generally, randomized controlled clinical trials of ICDs have excluded patients with significant noncardiac comorbidities. Patients with high overall baseline mortality have a higher proportion of nonsudden death. The majority of ICD implantations occur in primary prevention patients, who have a lower short-term risk of death. The follow-up in key ICD trials usually was between 3 and 5 years. Over the period of 3-5 years, patients at high risk of sudden death are most likely to benefit in terms of survival. Lower-risk populations derive little benefit over short follow-up due to their low event rate. However, when lower-risk patients were to be followed to 10-20 years, as the authors modeled in this article, it is the low-risk patients who have the greatest survival benefit. More conservative ICD programming (i.e., increasing the time to detection), which has been shown to improve survival over standard programming, may further increase the benefit to the ‘lower’ risk patients.
Keywords: Arrhythmias, Cardiac, Comorbidity, Death, Sudden, Defibrillators, Implantable, Follow-Up Studies, Heart Failure, Mortality, Primary Prevention, Risk, Survival
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