March 1, 2011Open Access
View Full PaperEffectiveness of Cardiac Resynchronization Therapy by QRS Morphology in the Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy (MADIT-CRT)
Key Result
CRT-D significantly reduced the risk of heart failure events or death compared to ICD alone in heart failure patients with LBBB (HR 0.47; P<0.001), but provided no benefit in non-LBBB patients.
Study Design
Type
RCT (n=1,817)
Multicenter
Yes
Structured PICO
Does CRT-D reduce heart failure events or death compared to ICD only in mild heart failure patients, and does this benefit depend on QRS morphology?
P
Population
1,817 heart failure patients with New York Heart Association class I or II and ejection fraction ≤ 30% with available sinus rhythm ECGs at baseline from the MADIT-CRT trial
I
Intervention
Cardiac resynchronization therapy with a defibrillator (CRT-D)
C
Comparator
Implantable cardioverter defibrillator (ICD) only
O
Outcome
Composite of heart failure event or deathcomposite
CRT-D provides substantial clinical benefit in mild heart failure patients with LBBB, but no benefit is observed in those with non-LBBB QRS patterns.
Main Result
Effect estimate: HR 0.47 (LBBB); HR 1.24 (non-LBBB)
p-value: p=<0.001 (LBBB); 0.257 (non-LBBB)
Abstract
BACKGROUND: This study aimed to determine whether QRS morphology identifies patients who benefit from cardiac resynchronization therapy with a defibrillator (CRT-D) and whether it influences the risk of primary and secondary end points in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) trial. METHODS AND RESULTS: Baseline 12-lead ECGs were evaluated with regard to QRS morphology. Heart failure event or death was the primary end point of the trial. Death, heart failure event, ventricular tachycardia, and ventricular fibrillation were secondary end points. Among 1817 patients with available sinus rhythm ECGs at baseline, there were 1281 (70%) with left bundle-branch block (LBBB), 228 (13%) with right bundle-branch block, and 308 (17%) with nonspecific intraventricular conduction disturbances. The latter 2 groups were defined as non-LBBB groups. Hazard ratios for the primary end point for comparisons of CRT-D patients versus patients who only received an implantable cardioverter defibrillator (ICD) were significantly (P < 0.001) lower in LBBB patients (0.47; P < 0.001) than in non-LBBB patients (1.24; P = 0.257). The risk of ventricular tachycardia, ventricular fibrillation, or death was decreased significantly in CRT-D patients with LBBB but not in non-LBBB patients. Echocardiographic parameters showed significantly (P < 0.001) greater reduction in left ventricular volumes and increase in ejection fraction with CRT-D in LBBB than in non-LBBB patients. CONCLUSIONS: Heart failure patients with New York Heart Association class I or II and ejection fraction ≤ 30% and LBBB derive substantial clinical benefit from CRT-D: a reduction in heart failure progression and a reduction in the risk of ventricular tachyarrhythmias. No clinical benefit was observed in patients with a non-LBBB QRS pattern (right bundle-branch block or intraventricular conduction disturbances). CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00180271.