RV function assessment
TAPSE was defined as the peak excursion of tricuspid annulus from end-diastole to end-systole, and was measured from the apical four-chamber view by placing the M-mode cursor through the lateral tricuspid annulus. TAPSE less than 17 mm indicated RV dysfunction [12].
The diameter changes of inferior vena cava (IVC) during the respiratory cycle were measured from the IVC long axis view by M-mode. The minimum diameter of the inferior vena cava (IVCmin) was measured in the inspiratory phase and the maximum diameter of the inferior vena cava (IVCmax) was measured in the expiratory phase when breathing spontaneously. The inferior vena cava collapse index (ICV-CI) was calculated by the formula of (IVCmax-IVCmin) / IVCmax × 100%.
The diameter of pulmonary artery (PAD) was measured from parasternal short-axis view by two-dimensional echocardiography. Tricuspid valve regurgitation pressure gradient biggest (TRPG) was measured and pulmonary arterial systolic pressure (PASP) was estimated indirectly by tricuspid regurgitation velocity with the addition of right atrial pressure, assuming no significant right ventricular outflow tract (RVOT) obstruction.