Cardiac resynchronization therapy with or without anatomical reverse remodeling does not affect defibrillation threshold.

Background: Recent clinical trials have documented beneficial reverse-remodeling effects with cardiac resynchronization therapy (CRT). The aim of this study was to investigate the effect of CRT with or without reverse anatomical remodeling of the left ventricle on defibrillation threshold (DFT) levels in a prospective and consecutive group of patients with class II-IV systolic heart failure.

Methods: Study population consisted of 29 patients (14 women and 15 men; mean age 61±11 years old). All patients underwent baseline (within 24-hours of cardiac resynchronization therapy-defibrillator [CRT-D] implantation) and 6-month follow-up DFT testing. Reverse anatomical remodeling of the left ventricle was defined as ≥15% reduction in left ventricular end-systolic volume at the end of 6 months of follow-up compared to baseline.

Results: Baseline, average DFT was 8.8±5.9 J. Left ventricular end-diastolic volume was the only predictor of baseline DFT level (P=0.02) among the baseline demographics. Safety margin of at least 10 J was achieved in all patients. Average DFT at the end of 6 months of biventricular pacing was 9.2±6.9 J. One patient (3.4%) failed to have a safety margin of 10 J. Reverse anatomical remodeling was observed in 14 (48%) patients and did not have any effect on DFT level. There were no complications related to DFT testings.

Conclusions: Baseline average DFT in patients undergoing CRT-D was ≤10 J in our study. CRT-D with or without anatomical reverse remodeling does not affect DFT at the end of 6 months of follow-up. High DFT level at the end of 6 months of follow-up is rare (3.4%) among patients with current CRT-D devices.