Usefulness of cardiac resynchronisation therapy in patients with right bundle branch block: is viability an important piece of the puzzle?

BACKGROUND Benefits of cardiac resynchronisation therapy (CRT) in patients with heart failure (HF) and left bundle branch block (LBBB) have been well established. The presence of asynchronism and viability predicts response to CRT with good accuracy. Viability in the region of the pacing lead as predictor of response to CRT in patients with HF, intraventricular asynchrony and right bundle branch block (RBBB) has never been evaluated. METHODS We studied 4 consecutive patients with RBBB (QRS>120 ms) advanced ischemic HF, low ejection fraction (≤35%) and intraventricular asynchrony ≥50 ms scheduled for CRT. Dobutamine stress echocardiography (DSE) was performed within the week before CRT. Viability was defined as increased wall thickening during DSE. Viability in the region of left ventricular (LV) pacing lead was defined as the presence of viability in 2 contiguous segments. Response was defined by LV reverse remodeling (i.e. ≥15% reduction in LV end-systolic volume) 3-6 months after CRT. RESULTS Three patients demonstrated LV reverse remodeling at follow-up. Responders showed LV end-systolic volume decrease of -31 ± 16% from baseline to follow-up whereas no change was observed in the non responder patient. Similar LV asynchronism was found in all patients. All responders had viability in ≥2 segments in the region of LV pacing. CONCLUSION This preliminary report suggests that similar reverse remodeling can be observed in RBBB patients as patients with LBBB after CRT. Intraventricular asynchrony and RBBB, viability in the region of pacing lead may help to predict response to CRT in patients with HF.