Comparative Effectiveness of Cardiac Resynchronization Therapy With an Implantable Cardioverter-Defibrillator Versus Defibrillator Therapy Alone: A Cohort Study

Study Questions:

What are the clinical outcomes after cardiac resynchronization therapy with a defibrillator (CRT-D) versus implantable cardioverter-defibrillator (ICD) only therapy in real-world practice?


This was a retrospective cohort study using the National Cardiovascular Data Registry’s ICD Registry linked with Medicare claims. There were 780 US hospitals implanting both CRT-D and ICD devices. There were 7,090 propensity-matched patients older than 65 years with reduced left ventricular ejection fraction (<0.35) and prolonged QRS duration (>120 ms) having CRT-D or ICD implantation between April 1, 2006 and December 31, 2009. Death, readmission, and device-related complications over 3 years were tracked.


Compared with ICD therapy, CRT-D was associated with lower risks for mortality (cumulative incidence, 25.7% vs. 29.8%; adjusted hazard ratio [HR], 0.82; 99% confidence interval [CI], 0.73-0.93), all-cause readmission (cumulative incidence, 68.6% vs. 72.8%; adjusted HR, 0.86; 95% CI, 0.81-0.93), cardiovascular readmission (cumulative incidence, 45.0% vs. 52.4%; adjusted HR, 0.80; 95% CI, 0.73-0.88), and heart failure readmission (cumulative incidence, 24.3% vs. 29.4%; adjusted HR, 0.78; 95% CI, 0.69-0.88). It was also associated with greater risks for device-related infection (cumulative incidence, 1.9% vs. 1.0%; adjusted HR, 1.90; 95% CI, 1.07-3.37). The lower risks for heart failure readmission associated with CRT-D compared with ICD therapy were most pronounced among patients with left bundle branch block or a QRS duration of ≥150 ms, and in women.


In older patients with reduced left ventricular ejection fraction and prolonged QRS duration, CRT-D was associated with lower risks for death and readmission than ICD therapy alone.


Questions often arise about the applicability of positive findings from clinical trials to the real-world patient care environment. This is particularly true when potential benefits observed in randomized clinical trials are extrapolated to older and sicker populations. The current study is valuable because it provides evidence of CRT-D efficacy in contemporary practice. In this observational study, patients who were eligible for CRT-D according to established criteria and who received CRT-D had significantly lower risks for death and readmission than those who received ICD therapy alone.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Acute Heart Failure

Keywords: Registries, Patient Care, Heart Failure, Bundle-Branch Block, Stroke Volume, Medicare, Defibrillators, Implantable

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