Evaluation of Left Ventricular Systolic Function Using Layer-Specific Strain in Rats Performing Endurance Exercise: A Pilot Study

OBJECTIVE: The functional characteristics of exercise-induced myocardial hypertrophy were studied in a rat model in conjunction with ultrasound layered strain technique to investigate the hidden changes in the heart brought about by exercise. METHODS: Forty specific pathogen free (SPF) adult Sprague-Dawley rats were selected and randomly divided into two groups of 20 exercise and 20 control rats. The longitudinal and circumferential strain parameters were measured using the ultrasonic stratified strain technique. The differences between the two groups and the predictive effect of stratified strain parameters on left ventricular systolic function were analyzed. RESULTS: The exercise group had significantly higher global endocardial myocardial longitudinal strain (GLSendo), global mid-myocardial global longitudinal strain (GLSmid) and global endocardial myocardial global longitudinal strain (GCSendo) values than the control group (p < 0.05). Even though global mid-myocardial circumferential strain (GCSmid) and global epicardial myocardial circumferential strain (GCSepi) were higher in the exercise group than in the control group, statistical significance was not reached (p > 0.05). Conventional echocardiography parameters were well correlated with GLSendo, GLSmid, and GCSendo (p < 0.05). GLSendo was the best predictor of left ventricular myocardial contractile performance in athletes determined using the receiver operating characteristic curve, with an area under the curve of 0.97, sensitivity of 95% and specificity of 90%. CONCLUSION: Rats performing endurance exercise exhibited subclinical changes in the heart after prolonged high-intensity exercise. A stratified strain parameter, GLSendo, played an important role in the evaluation of LV systolic performance in exercising rats.