on behalf of the MADIT-CRT InvestigatorsBackground-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 (PϽ0.001) lower in LBBB patients (0.47; PϽ0.001) than in non-LBBB patients (1.24; Pϭ0.257). 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 (PϽ0.001) 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 Յ30% 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.
Background-An important determinant of successful cardiac resynchronization therapy for heart failure is the position of the left ventricular (LV) pacing lead. The aim of this study was to analyze the impact of the LV lead position on outcome in patients randomized to cardiac resynchronization-defibrillation in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) study. Methods and Results--The location of the LV lead was assessed by means of coronary venograms and chest x-rays recorded at the time of device implantation. The LV lead location was classified along the short axis into an anterior, lateral, or posterior position and along the long axis into a basal, midventricular, or apical region. The primary end point of MADIT-CRT was heart failure (HF) hospitalization or death, whichever came first. The LV lead position was assessed in 799 patients, (55% patients Ն65 years of age, 26% female, 10% LV ejection fraction Յ25%, 55% ischemic cardiomyopathy, and 71% left bundle-branch block) with a follow-up of 29Ϯ11 months. The extent of cardiac resynchronization therapy benefit was similar for leads in the anterior, lateral, or posterior position (Pϭ0.652). The apical lead location compared with leads located in the nonapical position (basal or midventricular region) was associated with a significantly increased risk for heart failure/death (hazard ratioϭ1.72; 95% confidence interval, 1.09 to 2.71; Pϭ0.019) after adjustment for the clinical covariates. The apical lead position was also associated with an increased risk for death (hazard ratioϭ2.91; 95% confidence interval, 1.42 to 5.97; Pϭ0.004). Conclusion-LV leads positioned in the apical region were associated with an unfavorable outcome, suggesting that this lead location should be avoided in cardiac resynchronization therapy. Clinical Trial Registration-URL: http://clinicaltrials.gov.
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