PAP will be calculated as the sum of tricuspid regurgitation gradient and estimated right atrial pressure, provided there is no increase in pulmonic valve flow velocity .Maximal tricuspid regurgitation velocity (taken from all available views) will be measured by continuous wave Doppler echocardiography to evaluate the pressure gradient from the right ventricle to the right atrium. Right atrial pressure will be estimated on the basis of inferior vena cava (IVC) size and inspiratory collapse (7,8).