2.4. Calculation of the relevant echocardiography parameters

The echocardiographic examination was performed using an ultrasound machine (CX50, Philips Ultrasound System) to acquire the data of the left ventricle (LV). Images were saved digitally for subsequent offline analysis using QLAB software (QLAB 10.5; Philips Healthcare). Measurements of LV dimensions and volumes were performed by a computerized analysis software system. Ejection fraction (EF) was calculated using the LV volume data. Mitral inflow from the tips level was analyzed for peak early diastolic velocity (E) and late diastolic velocity (A), and E/A. Mitral annulus early diastolic velocity (e′) was measured at the septal and lateral mitral annulus, and the E/e′ ratio was calculated by the mean septal E/e′ ratio and mean lateral E/e′ ratio. Effective arterial elastance (Ea) and end‐systolic elastance (Ees) were computed by SBP × 0.9/stroke volume and SBP × 0.9/end‐systolic volume (ESV), while ventricular‐arterial decoupling (VAC) was the ratio of Ea and Ees. ¹² We used a two‐dimensional ultrasound speckle tracking imaging technique to measure LV torsion, LV untwisting rate, and LV strain. The computer automatically selects suitable stable objects for tracking and then searches for them in the next frame using a sum of absolute differences algorithm. We defined LV torsion as the difference between the apical and basal angle during systole around the longitudinal LV axis relative to the starting position and the untwisting rate was the maximum untwisting velocity calculated by the angle during diastole. ¹³ The global longitudinal strain (GLS) was calculated by averaging all the values of the regional peak longitudinal strain obtained in two‐chamber, three‐chamber, and four‐chamber apical views. The global circumferential strain (GCS) was assessed as the average of the three LV regional values measured in the parasternal short‐axis view at the basal level. Measurements of three cardiac cycles were averaged.