Improving Use of Primary Prevention ICDs

Study Questions:

Does the previously developed and validated Seattle Proportional Risk Model (SPRM) identify clinically important variations in the magnitude of implantable cardioverter-defibrillator (ICD) survival benefit in a primary prevention population?


Using the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial) database, the authors tested the SPRM-predicted probability of sudden death relative to that of nonsudden death. A Cox proportional hazards model was used.


The SPRM was much better than the Seattle Heart Failure Model at partitioning treatment benefit from ICD therapy (effect size was 2- to 3.6-fold larger for the ICDxSPRM interaction). ICD benefit varied significantly across SPRM-predicted risk quartiles: for all-cause mortality, a +10% increase with ICD therapy in the first quartile (highest risk of death, lowest proportion of sudden death) to a decrease of 66% in the fourth quartile (lowest risk of death, highest proportion of sudden death; p = 0.0013); for sudden death mortality, a 19% reduction in SPRM quartile 1 to 95% reduction in SPRM quartile 4 (p < 0.0001).


In symptomatic systolic heart failure patients with a Class I recommendation for primary prevention ICD therapy, the SPRM offers a useful patient-centric tool to guide shared decision making.


This report addresses the variations in the magnitude of survival benefit with a primary prevention ICD. The authors have previously developed and validated SPRM in patients with heart failure and reduced ejection fraction to predict variations in sudden cardiac death survival benefit. The previously developed SPRM model contains 10 variables: age, sex, New York Heart Association class, ejection fraction, diabetes mellitus, hyponatremia, systolic blood pressure, creatinine, body mass index, and digoxin use.

It is intriguing that the ICD benefit for sudden death prevention varied from 19% to 95%, while the risk of sudden death and appropriate ICD shocks did not vary across the risk quartiles of the SPRM. It is the nonarrhythmic deaths that determined the probability of survival across the quartiles.

The analysis shows that the ICD benefit varies with the SPRM for all-cause mortality and sudden death, with a greater benefit in those with a higher proportion of sudden death among all deaths. The implications are that in some patients, potentially identified by SPRM, who nominally qualify for ICD implantation based on SCD-HeFT entry criteria, the ICD might actually increase the chances of death.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Chronic Heart Failure

Keywords: Arrhythmias, Cardiac, Death, Sudden, Cardiac, Defibrillators, Implantable, Heart Failure, Heart Failure, Systolic, Primary Prevention, Risk, Stroke Volume

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