Response to preventive cardiac resynchronization therapy in patients with ischaemic and nonischaemic cardiomyopathy in MADIT-CRT

AimsThere are no data regarding the differential response to cardiac resynchronization therapy with defibrillator (CRT-D) by the aetiology of cardiomyopathy in mildly symptomatic patients. We evaluated the outcome of patients enrolled in MADIT-CRT by ischaemic and non-ischaemic aetiology of cardiomyopathy (ICM and non-ICM, respectively).Methods and resultsThe clinical response to CRT-D was assessed among ICM (n 1046) and non-ICM (n=774) patients enrolled in MADIT-CRT during an average follow-up of 2.4 years, and echocardiographic response was assessed at 1 year. Cardiac resynchronization therapy with defibrillator vs. ICD therapy was associated with respective 34 (P=0.001) and 44 (P=0.002) reductions in the risk of heart failure or death among ICM and non-ICM patients (P for interaction 0.455). In the ICM group, CRT-D was associated with mean (±SD) 29 ± 14 and 18 ± 10 reductions in left ventricular end-systolic volume (LVESV) and left ventricular end-diastolic volume (LVEDV), respectively. In the non-ICM group, CRT-D was associated with significantly greater volume reductions compared with the ICM group [37 ± 16 and 24 ± 12 reductions in LVESV and LVEDV, respectively (P < 0.001 for all)]. Risk subsets in the ICM group that showed a favourable clinical response to CRT-D included patients with QRS ≥150 ms, systolic blood pressure <115 mmHg, and left bundle branch block (LBBB), whereas in the non-ICM group females, patients with diabetes mellitus, and LBBB, displayed a favourable clinical response.ConclusionMildly symptomatic ICM and non-ICM patients show significant differences in the echocardiographic response to CRT-D and in the clinical benefit within risk subsets suggesting that risk assessment for CRT-D in this population should be aetiology-specific.