Background: Cardiac resynchronisation therapy improves peak oxygen uptake (peak VO2) 3–9 months after device implantation. In chronic heart failure, total isovolumic time (t-IVT) is a major determinant of peak VO2 and of cardiac output at peak dobutamine stress. In selected patients, resynchronisation can instantaneously shorten t-IVT. We sought to determine the acute effect of resynchronisation on exercise performance and determine, with pharmacological stress echocardiography, the mechanism underlying this effect.
Methods and results: Twenty-two patients with resynchronisation were studied within 3 months after device implantation. On a single study day, sequential cardiopulmonary exercise tests were performed during native activation (left bundle branch block) and resynchronisation (atrio-biventricular pacing) in random order. Total-IVT and cardiac output (at rest and peak dobutamine stress) were then measured in each activation mode.
Resynchronisation acutely increased peak VO2 by 1.6 (SD 1.5) ml/kg/min (p<0.001) and shortened peak stress t-IVT by 10 (SD 7) s/min (p<0.001), with the effects in individual patients showing a correlation (r = –0.46, p<0.05). Amongst all measurements during native activation, the best predictor of gain in peak VO2 from resynchronisation was peak stress t-IVT (r = 0.71, p<0.001) with every increment of 5 s/min of peak stress t-IVT during native activation predicting an 8% gain in peak VO2. No conventional measures during native activation at rest or on stress (including QRS duration, Tei index, tissue Doppler intraventricular delay, and resting t-IVT) added significant additional information.
Conclusions: In eligible patients, resynchronisation can acutely augment peak VO2, possibly through a mechanism of t-IVT shortening. Under native activation, long t-IVT during peak stress is the single best predictor of acute resynchronisation-mediated increment in peak VO2.
- exercise performance
- stress echocardiography
- total isovolumic time
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.
Competing interests: None.