Bundle-branch block morphology and other predictors of outcome after cardiac resynchronization therapy in Medicare
Kenneth C Bilchick1, Sandeep Kamath, John P DiMarco
1Departments of Medicine, University of Virginia Health System, PO Box 800158, Charlottesville, VA 22901, USA. bilchick@virginia.edu
Insights
Right bundle-branch block (RBBB), ischemic cardiomyopathy, advanced heart failure, and older age predict poor outcomes in cardiac resynchronization therapy (CRT) patients. Real-world CRT-D mortality rates are higher than previously reported.
Area of Science:
- Cardiology
- Medical Devices
- Public Health
Background:
- Clinical trials for cardiac resynchronization therapy (CRT) often exclude specific patient subgroups, like those with right bundle-branch block (RBBB).
- Population-based outcome analysis is crucial for identifying real-world predictors of CRT effectiveness.
Purpose of the Study:
- To identify predictors of outcomes in a large, real-world population of Medicare patients receiving cardiac resynchronization therapy with an implantable cardioverter-defibrillator (CRT-D).
Main Methods:
- Utilized Medicare Implantable Cardioverter-Defibrillator Registry data (2005-2006) merged with patient outcomes.
- Employed Cox proportional-hazards models to assess mortality and heart failure hospitalization in 14,946 CRT-D patients.
- Analyzed predictors including New York Heart Association (NYHA) class, age, RBBB, ischemic cardiomyopathy, and QRS duration.
Main Results:
- 1-year, 3-year, and overall mortality rates were 12%, 32%, and 37%, respectively, with a median follow-up of 40 months.
- NYHA class IV and age ≥ 80 years were significant predictors of early and late mortality.
- Right bundle-branch block (RBBB) and ischemic cardiomyopathy were also strong predictors of mortality, with RBBB and ischemic cardiomyopathy combined showing twice the hazard of death compared to left bundle-branch block and non-ischemic cardiomyopathy.
Conclusions:
- Right bundle-branch block (RBBB), ischemic cardiomyopathy, NYHA class IV status, and advanced age are significant predictors of adverse outcomes in Medicare patients treated with CRT-D.
- Real-world mortality rates observed 3-4 years post-CRT-D implantation appear higher than previously recognized in clinical trial data.
Background:
Clinical trials of cardiac resynchronization therapy (CRT) have enrolled a select group of patients, with few patients in subgroups such as right bundle-branch block (RBBB). Analysis of population-based outcomes provides a method to identify real-world predictors of CRT outcomes.
Methods And Results:
Medicare Implantable Cardioverter-Defibrillator Registry (2005 to 2006) data were merged with patient outcomes data. Cox proportional-hazards models assessed death and death/heart failure hospitalization outcomes in patients with CRT and an implantable cardioverter-defibrillator (CRT-D). The 14 946 registry patients with CRT-D (median follow-up, 40 months) had 1-year, 3-year, and overall mortality rates of 12%, 32%, and 37%, respectively. New York Heart Association class IV heart failure status (1-year hazard ratio [HR], 2.23; 3-year HR, 1.98; P<0.001) and age ≥ 80 years (1-year HR, 1.74; 3-year HR, 1.75; P<0.001) were associated with increased mortality both early and late after CRT-D. RBBB (1-year HR, 1.44; 3-year HR, 1.37; P<0.001) and ischemic cardiomyopathy (1-year HR, 1.39; 3-year HR, 1.44; P<0.001) were the next strongest adjusted predictors of both early and late mortality. RBBB and ischemic cardiomyopathy together had twice the adjusted hazard for death (HR, 1.99; P<0.001) as left BBB and nonischemic cardiomyopathy. QRS duration of at least 150 ms predicted more favorable outcomes in left BBB but had no impact in RBBB. A secondary analysis showed lower hazards for CRT-D compared with standard implantable cardioverter-defibrillators in left BBB compared with RBBB.
Conclusions:
In Medicare patients, RBBB, ischemic cardiomyopathy, New York Heart Association class IV status, and advanced age were powerful adjusted predictors of poor outcome after CRT-D. Real-world mortality rates 3 to 4 years after CRT-D appear higher than previously recognized.
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