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

Summary

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.