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

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 analyzed at both global and segmental levels using advanced deformation echocardiographic imaging techniques. One hundred AMI patients were randomly assigned to participate in an 8-week training program 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 (LS) and circumferential (CS) strains and torsional mechanics, LV myocardial work (MW) and mechanical dispersion (post-systolic shortenings, PSS) indexes as well as atrial strains. Mixed models were used to evaluate the effect of MICT and HIIT on STE 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% 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 2 groups. These improvements were observed in all myocardial territories, regardless of previous ischemic 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. Early supervised exercise-based CR, whether using MICT or isovolumic HIIT, improves longitudinal myocardial function in both culprit and non-culprit territories after AMI.