Which vein has the highest oxygen saturation?

Renal vein has the highest oxygen saturation. Hence the inferior vena caval (IVC) blood is more saturated than superior vena caval blood. The saturation is higher in the inferior vena cava above the renal veins (high IVC) than the low IVC.

Which vein has the lowest oxygen saturation?

Coronary sinus has the lowest oxygen saturation as the oxygen extraction is maximum in the coronary circulation. Coronary sinus saturation does not fall with exercise as the extraction reserve is fully utilized in the coronary circulation and increase in oxygen consumption can occur only by increasing the flow.

In which situation is coronary sinus saturation elevated?

Total anomalous pulmonary venous drainage into the coronary sinus (intracardiac variety of TAPVC) causes elevated oxygen saturation in the coronary sinus blood.

How can you estimate the pulmonary artery mean pressure by Doppler echo?

The early diastolic pulmonary regurgitation (PR) gradient (peak PR gradient) will give an estimate of mean pulmonary artery pressure. End diastolic gradient of PR will give an estimate of pulmonary artery end diastolic pressure (diastolic pressure). Ideally the right ventricular end diastolic pressure has to be added to the end diastolic PR gradient to get the pulmonary artery diastolic pressure. Tricuspid regurgitation jet gradient gives an estimate of right ventricular systolic pressure. The right atrial pressure added to the peak TR gradient gives the right ventricular systolic pressure, which will be equal to the pulmonary artery systolic pressure in the absence of right ventricular outflow tract obstruction.