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Updated: Jun 25, 2026
Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
Published on: December 11, 2017
A mechanistic investigation into how long-term resynchronization therapy confers ongoing cardiac functional benefits
Dominik Schlosshan1, Diane Barker, Nigel Lewis
1Academic Unit of Molecular Cardiovascular Medicine, University of Leeds, Leeds, United Kingdom.
Insights
Cardiac resynchronization therapy (CRT) benefits persist during exercise, improving cardiac function and capacity. Temporary CRT deactivation significantly reduced peak exercise performance in heart failure patients.
Area of Science:
- Cardiology
- Biomedical Engineering
- Exercise Physiology
Background:
- Long-term benefits of cardiac resynchronization therapy (CRT) mechanisms remain unclear.
- The impact of ongoing ventricular resynchronization on cardiac function requires further investigation.
Purpose of the Study:
- To investigate the functional benefits of CRT during peak exercise.
- To assess the effects of temporary CRT cessation on cardiac function in heart failure patients.
Main Methods:
- A randomized, double-blind, crossover trial involving 15 severe heart failure patients with CRT devices.
- Central hemodynamic measurements, including noninvasive cardiac output, were taken during exercise tests with CRT on and off.
- Patients underwent crossover testing on separate days to compare both conditions.
Main Results:
- Temporary CRT deactivation led to a 19% decrease in peak exercise cardiac power and an 11.5% reduction in peak cardiac output.
- Exercise capacity was diminished, with lower peak oxygen uptake and shorter exercise duration when CRT was off.
- No significant hemodynamic changes were observed at rest, irrespective of CRT status.
Conclusions:
- Left ventricular resynchronization via CRT confers significant cardiac functional benefits during peak exercise.
- These benefits are not apparent at rest, highlighting the importance of CRT for exercise performance in heart failure.
Abstract:
The exact mechanisms underpinning the longer term benefits of cardiac resynchronization therapy (CRT) were not fully understood. It was still unclear whether there was any ongoing functional benefit conferred by the partial resynchronization of ventricular contraction. To resolve this, a randomized controlled double-blind crossover trial was conducted to investigate the impact of temporary cessation of CRT on cardiac function both at rest and during peak exercise. Fifteen patients with severe heart failure and a CRT device implanted at least 3 months previously were randomly assigned to have the CRT mode switched to either off or on during exercise tests with central hemodynamic measurements (including noninvasive cardiac output measured using rebreathing methods), then crossed over on separate days to the opposite CRT mode. There were no significant changes in hemodynamic variables at rest with either mode of CRT. When CRT was acutely turned off, there was 19% lower peak exercise cardiac power (2.10 +/- 0.46 vs 2.59 +/- 0.75 W; p <0.005), 6% lower mean arterial pressure (92 +/- 12 vs 98 +/- 13 mm Hg; p <0.05), and 11.5% lower peak cardiac output (10.4 +/- 1.9 vs 11.8 +/- 2.5 L/min; p <0.05). Exercise capacity was also diminished with lower peak oxygen uptake (15.7 +/- 4.3 vs 17.2 +/- 4.9 ml/kg/min; p <0.01) and shorter exercise duration (542 +/- 204 vs 587 +/- 212 seconds; p <0.05). These changes were seen without differences in peak respiratory exchange ratio and peak systemic vascular resistance. In conclusion, these observations provided evidence that after CRT, left ventricular resynchronization continued to confer cardiac functional benefits manifest during peak exercise, but imperceptible at rest.
