Evaluate To Kinetics Of Myocardial Strain During Isovolumic Relaxation Using Speckle-tracking During Exercise In Healthy Subjects

Objective To observe the subendocardial and subepicardial layers circumferential strain and circumferential strain recovery rate during isovolumic relaxation (IVR) using speckle-tracking during exercise in healthy subjects, discusses the valuation of circumferential strain recovery rate during IVR for defining left ventricular diastolic function.Methods Exercise stress test by using the improved Bruce scheme. Echocardiography was performed in43healthy students sedentary subjects at rest, maximal aerobic power and recovery after exercise. The parameters of of peak early-diastolic mitral orifice flow velocity (E), peak early-diastolic mitral annular velocity in left ventricular posterior wall (e) and heart diastolic function (E/e) were measured. Collection and storage of left ventricular basal, papillary muscle and apical short-axis view of dynamic image. Sub endocar dial and subepicardial layers circumferential strain of three short-axis during end systole (ES) and end isovolumetric relaxation (IRA) were analyzed using Xstrain software. Calculation of subepicardial myocardial circumferential strain recovery rate during IVR (ENCS-rec, EPCS-rec). Comparison sub endocar dial and subepicardial layers circumferential strain of three short-axis during ES and IRA phases, and ENCS-rec and EPCS-rec in different exercise phases. To analyze the relationship between circumferential strain recovery rate during IVR and E/e.Results①Subendocardial and subepicardial layers circumferential strain of the basal, papillary level short-axis during ES and IRA phases decreased first and then increased with exercise intensity (P<0.05); Subendocardial myocardial circumferential strain greater than subepicardial myocardium circumferential strain of3short-axis during ES and IRA phases in different exercise phases (P<0.01).②ENCS-rec and EPCS-rec of3short-axis increased first and then decreased with exercise intensity (P<0.05); EPCS-rec greater than ENCS-rec of basal short-axi at rest (P<0.05).③ENCS-rec and EPCS-rec of3short-axis relaxation E/e in different exercise phases (P<0.05).Conclusion①In normal subjects, subepicardial and subepicardial layers circumferential strain and recovery rate consistent with myocardial physiological change during IVR in different exercise phases.②During IVR, the different myocardial layers circumferential strain and recovery rate have difference.③The evaluation of LV myocardial circumferential strain recovery rate during IVR is therefore of significant interest to assess diastolic function.