Peak oxygen uptake during cardiopulmonary exercise testing determines response to cardiac resynchronization therapy.

Background: Cardiac resynchronization therapy (CRT) is an established treatment modality for advanced heart failure (HF) but 20-30% of patients treated with CRT do not experience clinical improvement. Hence, in this study we aimed to investigate whether baseline cardiopulmonary exercise testing (CPX) can help improve the prediction of a positive functional CRT response.

Methods: This prospective observational study included 76 HF patients undergoing elective CRT implantation and clinical CPX and echocardiographic assessment were performed at baseline, 6, and 12 months.

Results: Peak VO2 increased from 11.0±2.5 ml/min/kg to 12.0±4.1 ml/min/kg and 12.2±3.5 ml/min/kg at 6 and 12 months after CRT, respectively. The number of patients classified as "CRT-responders" (Δ peak VO2≥1 ml/kg/min) was 33 (46%) and 36 (52%) at 6 and 12 months after CRT, respectively. Patients with baseline peak VO2<40% of predicted (lowest tertile) demonstrated a 68% and 69% response rate at 6 and 12 months, respectively, as compared to a 35% and 42% response rate among patients with baseline peak VO2≥40% of predicted (p=0.01 and p=0.02, respectively). In multivariate analysis patients with baseline peak VO2<40% of predicted had an adjusted odds ratio of 4.4 (95% CI 1.6-12.5; p<0.01) and 3.1 (95% CI 1.1-8.8; p=0.03) for positive CRT response at 6 and 12 months, respectively.

Conclusions: Treatment with CRT improves exercise capacity but this increase is most substantial among patients with a lower baseline peak VO2 (% of predicted). Baseline CPX can, therefore, be utilized to identify patients more likely to exhibit a functional improvement after CRT.