ICD Therapy in Ischemic vs. Nonischemic Cardiomyopathy

Quick Takes

  • In this pooled analysis of five primary prevention ICD trials of patients with cardiomyopathy, those with ischemic and nonischemic cardiomyopathy had a similar risk of rapid VT or VF.
  • The risk of all-cause mortality was significantly higher among patients with ischemic cardiomyopathy, even after adjustment for baseline demographic variables.

Study Questions:

What is the association of cardiomyopathy etiology with the likelihood of ventricular arrhythmias, appropriate implantable cardioverter-defibrillator (ICD) therapy, and mortality?

Methods:

Data on patient outcomes from five randomized trials of primary prevention ICD therapy were pooled. Endpoints such as sustained ventricular tachycardia (VT) or ventricular fibrillation (VF), appropriate ICD therapy, and all-cause mortality were analyzed.

Results:

There were 3,106 patients with ischemic cardiomyopathy (ICM) and 1,697 patients with nonischemic cardiomyopathy (NICM). Patients with ICM were significantly older and had more comorbid conditions, whereas those with NICM had a more advanced heart failure class at enrollment and were more often prescribed medical or cardiac resynchronization therapy for heart failure. Multivariate analysis showed that ICM versus NICM had a similar risk of VT/VF events (hazard ratio [HR], 0.98; 95% confidence interval [CI], 0.79-1.20) and appropriate ICD therapy (HR, 1.03; 95% CI, 0.87-1.22), whereas the risk of all-cause mortality was 1.8-fold higher among ICM versus NICM patients (HR, 1.84; 95% CI, 1.42-2.38), dominated by nonsudden cardiac mortality.

Conclusions:

Combined data from five landmark ICD clinical trials show that ICM patients experience a similar risk of life-threatening ventricular arrhythmic events but have an increased risk of all-cause mortality, dominated by nonsudden cardiac death, compared with NICM patients.

Perspective:

While ICD therapy is indicated for patients with both ICM and NICM, support for the ICD in primary prevention of sudden cardiac death is much stronger for patients with the ischemic disease. Prior pooled analyses of randomized trials showed benefits of an ICD in the setting of nonischemic disease, but the most recent study (DANISH) did not demonstrate a mortality reduction. The present analysis reaffirms similar likelihood of life-threatening ventricular arrhythmia in patients with both types of cardiomyopathies, with ischemic patients having a >2-fold increased risk of all-cause, cardiac, and noncardiac mortality compared with NICM patients. About 25% of patients receiving ICD therapy during the trials experienced potentially life-threatening ventricular arrhythmias. Further risk stratification for those who are unlikely to benefit from an ICD remains elusive and deserves more research.

Keywords: Arrhythmias, Cardiac, Cardiac Resynchronization Therapy, Cardiomyopathies, Death, Sudden, Cardiac, Defibrillators, Implantable, Geriatrics, Heart Failure, Myocardial Ischemia, Primary Prevention, Risk Assessment, Tachycardia, Ventricular, Ventricular Fibrillation


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