# The effect of cardiac resynchronization therapy on functional capacity based on cardiopulmonary exercise testing: a systematic review and meta-analysis

## TL;DR

This study finds that cardiac resynchronization therapy improves exercise capacity and breathing efficiency in heart failure patients, using cardiopulmonary exercise testing.

## Contribution

The study provides a meta-analysis showing CRT's physiological benefits beyond cardiac remodelling, using CPET for personalized post-CRT care.

## Key findings

- CRT significantly improves peak VO₂, anaerobic threshold, and ventilatory efficiency.
- CPET can guide post-CRT optimization and identify patients at risk of advanced heart failure.
- Heterogeneity in results suggests variability in protocols and patient factors.

## Abstract

Cardiac resynchronization therapy (CRT) has a class 1a indication for patients with heart failure due to reduced ejection fraction (HFrEF) who also have conduction delay. Post-CRT management pathways are uncommon. Cardiopulmonary exercise testing (CPET) provides objective functional assessments and may serve as a valuable tool in assessing CRT response and guide device optimization. This systematic review and meta-analysis aimed to assess the effect of CRT on key CPET parameters and identify patients who may benefit from further intervention.

A systematic search of MEDLINE, EMBASE, and Cochrane Central (May 2024) identified randomized controlled trials, non-randomized trials, and cohort studies evaluating changes in CPET post-CRT. Primary outcome was peak VO₂, with anaerobic threshold and ventilatory efficiency as secondary outcomes. Results were reported as standardized mean differences (SMD) and effect sizes using Cohen’s d.

Fourteen studies (12 cohort studies and 2 RCTs) involving 858 patients were included. CRT was associated with significant improvements in peak VO₂ (SMD = 0.62, 95% CI 0.19–1.05, P < 0.001), anaerobic threshold (SMD = 0.70, 95% CI 0.03–1.36, P = 0.04), and ventilatory efficiency (SMD = −0.45, 95% CI −0.68 to −0.21, P < 0.001). Considerable heterogeneity was noted, likely reflecting differences in exercise protocols, patient characteristics, and device programming.

CRT improves exercise capacity and ventilatory efficiency, reinforcing its physiological benefits beyond cardiac remodelling. CPET may support personalized post-CRT care, including optimization of device programming, medications, and rehabilitation. Worsening CPET parameters may help identify patients progressing to advanced heart failure, allowing for timely care planning.

Graphical Abstract