Echocardiographic examination
Echocardiographic examinations were performed using an Aeroscan CD 25 ultrasound system with a phased-array sector transducer working at frequencies between 3.6 - 4.5 MHz with a maximum depth of 24 to 26 cm, a frame rate of 13 to 31 frames/ s and the focus point at 10 to 15 cm to obtain 2-D, M-mode and Doppler images of the heart, as per the procedure reported by Schwarzwald (2019).
Echocardiography was performed in right parasternal short-axis view at the level of the chordae tendinae. Echocardiographic indices including left ventricular internal diameter during diastole and systole (LVIDd and LVIDs), left ventricular posterior wall thickness during diastole and systole (LVPWd and LVPWs), Interventricular septum thickness during diastole and systole (IVSd and IVSs), end diastole volume (EDV), end systole volume (ESV), ejection fraction (EF), fractional shortening (FS), stroke volume (SV), aortic diameter (Ao) and left atrium in three cardiac cycles and the average values were recorded and compared between before and after exercise. Color doppler echocardiography (Gunther-Harrington et al. , 2018) was done1hour before and 5 min after exercise to identify valvular regurgitation.