Estimation of right ventricular / pulmonary artery systolic pressure is done by Doppler echocardiographic measurement of the tricuspid regurgitaion jet velocity. From the jet velocity, the gradient is calculated with the formula: Pressure gradient = 4V^2, where V is the velocity. Once the tricuspid regurgitation (TR) jet gradient is estimated, adding the expected right atrial pressure (nominal value taken as 10 mm Hg) gives the right ventricular systolic pressure (RVSP). If the right atrial pressue is elevated, a clinical estimate of right atrial pressure from the measured jugular venous pressure may be added to the gradient to get a better estimate of RVSP. When there is no obstruction at the pulmonary valve, RVSP gives a good estimate of the pulmonary artery systolic pressure as the gradient at the pulmonary valve is minimal. Estimates of the RVSP can be erroneous if a good envelope of the TR jet is not obtained. Incomplete jets lead to underestimation of RVSP. When there is cycle to cycle variation in jet gradient, an average of multiple values may be taken. TR is jet usually evaluated in the apical four chamber view.