The association between biventricular pacing and cardiac resynchronization therapy-defibrillator efficacywhen comparedwith implantable cardioverter defibrillatoronoutcomesandreverse remodelling

Abstract

Aims Previous studies on biventricular (BIV) pacing and cardiac resynchronization therapy-defibrillator (CRT-D) efficacy have used arbitrarily chosen BIV pacing percentages, and no study has employed implantable cardioverter defibrillator (ICD) patients as a control group. Methods and results UsingKaplan-Meier plots,we estimated the threshold ofBIV pacing percentage needed forCRT-Dto be superior to ICDon the end-point of heart failure (HF)or death in 1219 left bundle branch block (LBBB) patients in theMADIT-CRT trial. Patients were censored at the time of crossover. InmultivariableCox analyses, no differencewas seen in the risk ofHF/death between ICD and CRT-D patientswith BIV pacing ≤90%[HR=0.78 (0.47-1.30), P=0.344], and with increasing BIV pacing the risk of HF/deathwas decreased[CRT-DBIV91-96%vs. ICD:HR=0.63 (0.42-0.94), P=0.024 andCRT-D BIV ≥97%vs. ICD: HR=0.32 (0.23-0.44), P< 0.001]. The risk of death alone was reduced by 52% in CRT-D patients with BIV ≥97% (HR=0.48, P< 0.016),when comparedwith ICDpatients.Within the CRT-D group, for every 1 percentage point increase in BIV pacing, the risk of HF/death and death alone significantly decreased by 6 and 10%, respectively. Increasing BIV pacing percentage was associated with significant reductions in left ventricular volume. Conclusion In patients with LBBB, whowere in sinus rhythm at enrolment, BIV pacing exceeding 90%was associated with a benefit of CRT-D in HF/death when compared with ICD patients. Furthermore, BIV pacing ≥97% was associated with an even further reduction in HF/death, a significant 52% reduction in death alone, and increased reverse remodelling. Clinical trials.gov identifier: NCT00180271.