Effect of Clinical Risk Stratification on Cost-Effectiveness of the Implantable Cardioverter-Defibrillator: The Canadian Implantable Defibrillator Study

Background—Three randomized clinical trials showed that implantable cardioverter-defibrillators (ICDs) reduce the risk of death in survivors of ventricular tachyarrhythmias, but the cost per year of life gained is high. A substudy of the Canadian Implantable Defibrillator Study (CIDS) showed that 3 clinical factors, age ≥70 years, left ventricular ejection fraction ≤35%, and New York Heart Association class III, predicted the risk of death and benefit from the ICD. We estimated the extent to which selecting patients for ICD therapy based on these risk factors makes ICD therapy more economically attractive. Methods and Results—Patients in CIDS were grouped according to whether they had ≥2 of 3 risk factors. Incremental cost-effectiveness of ICD therapy was computed as the ratio of the difference in mean cost to the difference in life expectancy between the 2 groups. Over 6.3 years, the mean cost per patient in the ICD group was Canadian (C) $87 715 versus $38 600 in the amiodarone group (C$1≈US$0.67). Life expectancy for the ICD group was 4.58 years versus 4.35 years for amiodarone, for an incremental cost-effectiveness of ICD therapy of C$213 543 per life-year gained. The cost per life-year gained in patients with ≥2 factors was C$65 195, compared with C$916 659 with <2 risk factors. Conclusions—The cost-effectiveness of ICD therapy varies by patient risk factor status. The use of ICD therapy in patients who have ≥2 risk factors of age ≥70 years, left ventricular ejection fraction ≤35%, and NYHA class III is C$65 195 to gain a year of life.