A comprehensive analysis of the impact of high-intensity interval vs. moderate-intensity continuous training on global and regional myocardial function in patients early after acute myocardial infarction: the STRAICT randomized controlled trial

AIMS: This study aims to compare the effect of moderate-intensity continuous training (MICT) vs. isovolumic high-intensity interval training (HIIT) on left ventricular (LV) myocardial function early post-acute myocardial infarction (AMI). Training-induced changes were analysed at both global and segmental levels using advanced deformation echocardiographic imaging techniques. METHODS AND RESULTS: One hundred AMI patients were randomly assigned to participate in an 8-week training programme comprising either MICT (n = 50) or isovolumic HIIT (n = 50), starting within 6 weeks post-AMI. Before and after cardiac rehabilitation (CR), we carried out a comprehensive and detailed evaluation of myocardial function, including measurements of LV longitudinal strain (LS) and circumferential strain and torsional mechanics, LV myocardial work (MW) and mechanical dispersion [post-systolic shortenings (PSS)] indexes, and atrial strains. Mixed models were used to evaluate the effect of MICT and HIIT on speckle-tracking echocardiography parameter. Both MICT and HIIT resulted in a similar improvement in the amplitude and timing of LV LS (time effect P < 0.001 in each case), as depicted by the comparable increase in global LS [HIIT: -0.82%, 95% confidence interval (CI): -0.19/-61; MICT: -1.11%, 95% CI: -1.17/-0.51; time ∗ group P = 0.71], MW index and efficiency, constructive MW, and reduction in the number of PSS and wasted MW (time ∗ group P > 0.12 in each case) in the two groups. These improvements were observed in all myocardial territories, regardless of previous ischaemic risk status (culprit vessel-by-time-by-group interactions, P > 0.60 in each case). Circumferential strains remained unchanged in both groups while there was a trend (time ∗ group P = 0.04) for LV torsion to decrease for MICT (P = 0.06) and increase for HIIT (P = 0.36) after CR. Left atrial strains during the reservoir and conduit phases improved (time effect P < 0.05) similarly in MICT vs. HIIT (time ∗ group P > 0.54). V̇O2peak (P < 0.001) and quality of life (P < 0.001) improved equally in MICT and HIIT after CR. CONCLUSION: Early supervised exercise-based CR, whether using MICT or isovolumic HIIT, improves longitudinal myocardial function in both culprit and non-culprit territories after AMI.