Key result
High-intensity exercise reduces ventricular arrhythmia inducibility in post-MI rats vs controls.
Why the study?
Exercise training improves contractile function and can reduce arrhythmia burden post-MI, but how exercise modifies the proarrhythmic status remains uncertain.
Does an 8-week high-intensity exercise program reduce ventricular arrhythmia inducibility and alter electrophysiology in rats 6 weeks post-MI?
RCT
randomized
Does an 8-week high-intensity exercise program reduce ventricular arrhythmia inducibility and alter electrophysiology in rats 6 weeks post-MI?
Post-MI exercise in rats reduces ventricular arrhythmia inducibility and improves electrophysiological characteristics in both noninfarcted and scar regions, suggesting a mechanism for its anti-arrhythmic effects.
Answers are grounded in this paper and cite their sources.
Does not support changing post-MI exercise recommendations; hypothesis-generating for anti-arrhythmic effects and requires human trials.
BACKGROUND: Exercise training improves contractile function and can reduce arrhythmia burden after a myocardial infarction (MI). How exercise modifies the proarrhythmic status is uncertain. METHODS: In this study, rats 6 weeks post-MI were randomized to an 8-week high-intensity exercise program (MI-EX) or to a sedentary control group (MI-SED) and compared with a sedentary sham group (Sham-SED). After the exercise program, in vivo and ex vivo programmed electrical stimulation was performed on the rat hearts. Subsequently, optical mapping was conducted to electrophysiologically characterize the MI hearts. In vivo cardiac stimulation protocols indicated reduced inducibility of ventricular arrhythmias in MI-EX compared with MI-SED. This anti-arrhythmic effect was retained ex vivo in Langendorff-perfused hearts. Optical mapping of the noninfarcted left ventricle indicated a prolonged average action potential (AP) duration at 4.5 Hz pacing frequency in both MI groups compared with Sham-SED. As pacing frequency increased (6.5 Hz and ≈8 Hz), AP duration remained significantly longer in the MI-SED group but decreased in the MI-EX group, demonstrating a negative frequency dependency. Spatial heterogeneity of AP duration in the noninfarcted left ventricle area was increased post-MI but was significantly reduced following exercise. Optical AP recorded from the remnant myocardium within the scar showed similar AP duration characteristics at low stimulation frequencies, but AP upstroke time was shorter in the MI-EX group compared with MI-SED. CONCLUSIONS: Post-MI exercise was associated with electrophysiological changes in both the noninfarcted region and the remnant myocardium within the scar. These changes suggest a mechanism for the anti-arrhythmic effects of exercise following MI.
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Stølen et al. (2026) conducted an RCT in Myocardial infarction. High-intensity exercise program vs. Sedentary control was evaluated on Inducibility of ventricular arrhythmias and electrophysiological characteristics. An 8-week high-intensity exercise program reduced the inducibility of ventricular arrhythmias and improved electrophysiological characteristics in post-MI rats compared with sedentary controls.
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