Early intervention with cardiac resynchronization therapy with defibrillator (CRT-D) in mild heart failure (HF) patients with a left bundle branch block (LBBB) ECG pattern was associated with a significant reduction in mortality in the long-term MADIT-CRT trial. Whether patients in MADIT-CRT enrolled from centers in the USA and in Europe have different long-term clinical response to CRT-D remains unknown. We compared the baseline clinical characteristics and clinical and echocardiographic long-term clinical response to CRT-D between MADIT-CRT patients with LBBB who were enrolled in USA (n = 871) and European centers (n = 392). Although European patients had more advanced heart disease than US patients, CRT-D was associated with similar 60 % (p < 0.001) reductions in the risk of HF in US and European patients when compared to ICD-only therapy after adjustment for relevant baseline clinical covariates. US patients had significant long-term mortality reduction (38 %, p = 0.02) while among European patients the survival benefit associated with CRT-D was not statistically significant (HR 0.73, p = 0.18); subgroup analyses revealed a significantly greater CRT-D benefit among women who were enrolled in the USA, whereas no significant gender difference in the clinical benefit of CRT-D was observed in the European cohort. Reverse remodeling at 1 year was associated with significantly better clinical outcomes in both groups. Despite differences in baseline disease severity, European and US patients with LBBB experienced a similar clinical and echocardiographic response to cardiac resynchronization therapy during long-term follow-up.
Clinical trial registration: http://clinicaltrials.gov/ct2/show/NCT00180271 .