Effect of exercise training on left ventricular mechanics after acute myocardial infarction-an exploratory study

Background: Cardiac rehabilitation (CR) exercise training is beneficial after myocardial infarction (MI). Whilst the peripheral adaptations to training are well defined, little is known regarding the effect on left ventricular (LV) remodelling, particularly LV function. Efficient LV ejection and filling is achieved through deformation and rotation of the myocardium in systole and diastole - LV mechanics. The response of LV mechanics to CR exercise training in MI patients is unknown.

Methods: In this observational exploratory study, 36 (of 40 enrolled) male, MI patients completed either 10-weeks of twice-weekly gym based cardiovascular exercise at 60-80% VO_2peak (n=18), or a non-exercise control period (n=18). Cardiopulmonary exercise testing and speckle tracking echocardiography were performed at baseline and 10 weeks.

Results: Compared to the non-exercise group, VO_2peak improved with CR exercise training (Difference: +4.28 [95% CI: 1.34 to 7.23] ml.kg^-1.min^-1, P=0.01). Neither conventional LV structural or functional indices, nor LV global longitudinal strain, significantly changed in either group. In contrast, LV twist and twist velocity decreased in the exercise group and increased in the non-exercise group (Difference: -3.95° [95% CI: -7.92 to 0.03°], P=0.05 and -19.2°.s^-1 [95% CI: -35.9 to -2.7°.s^-1], P=0.02, respectively).

Conclusion: In MI patients who completed CR exercise training, LV twist and twist velocity decreased, whereas these parameters increased in patients who did not exercise. These preliminary data may indicate reverse LV functional remodelling and improved functional reserve. The assessment of LV twist may serve as an indicator of the therapeutic benefit of CR exercise training and should be investigated in larger trials.