Effects of High Intensity Interval Training Rehabilitation Protocol after an Acute Coronary Syndrome on Myocardial Work and Atrial Strain

Background andObjectives: Current guidelines on cardiac rehabilitation (CR) suggest moderate-intensity physical activity after acute coronary syndrome (ACS). Recent report have shown that high-intensity interval training (HIIT) could be more effective than moderate-intensity continuous training (MCT) in improving cardiac performance. Our aim was to analyze the effects of HIIT protocol after ACS on advanced echocardiographic parameters of myocardial function. Materials and Methods: In total, 75 patients with recent ACS, with or without ST segment elevation, were enrolled and compared with a control group of 50 age- and sex-comparable healthy subjects. Patients were randomized to perform a MCT training or HIIT-based rehabilitation program. A complete echocardiographic evaluation, including left ventricular (LV) and left atrial (LA) global longitudinal strain (GLS) and myocardial work (MW) through speckle-tracking analysis, was performed for all patients, before and after cardiac rehabilitation training. A cardiopulmonary exercise testing (CPET) was also performed at the end of the rehabilitation program. Results: Patients who followed the HIIT rehabilitation program showed improved LV diastolic function compared to the MCT group (E/e’: 3.4 ± 3.1 vs. 6.4 ± 2.8, respectively, p < 0.01). Similarly, LV systolic function showed significant improvement in the group of patients performing HIIT (ejection fraction: 53.1 ± 6.4 vs. 52.3 ± 5.4%, p < 0.01; GLS: −17.8 ± 3.8 vs. −15.4 ± 4.3, p < 0.01). In addition, LA strain was improved. MW efficiency was also increased in the HIIT group (91.1 ± 3.3 vs. 87.4 ± 4.1%, p < 0.01), and was closely related to peak effort measurements expressed in peak VO2 by CPET. Conclusions: In patients with recent ACS, the HIIT rehabilitation program determined reverse cardiac remodeling, with the improvement of diastolic and systolic function, assessed by standard echocardiography. In addition, cardiac deformation index as GLS, LA strain and MW efficiency improved significantly after HIIT, and were associated with functional capacity during effort.