A patent ductus arteriosus (PDA) is a persistent connection ... is an average of a 95 mmHg gradient causing a left to right shunt and during diastole there is a 75 mmHg gradient causing a similar ...

Both of these are confounded when there is an atrial shunt, hence limiting the use of relative ventricular output as a measure of PDA significance. This shows the measurement of the color Doppler ...