Case 39

Pulsed wave Doppler

This image shows flow velocity across the tricuspid valve in diastole. Note that during mid- and late diastole the flow velocity is almost perfectly steady at around 1.5 m/s. Then during atrial systole the velocity increases remarkably as the right atrium contracts to push more blood into the right ventricle. When this occurs, the velocity shoots upward to around 3 m/s. This means that during late diastole, the right atrial pressure is around 36 mmHg (3 squared times 4; modified Bernoulli equation) higher in the right atrium than it is in the right ventricle. Normal right atrial pressure is 5 mmHg or less. This should be seen as jugular vein pulsation on physical exam but wasn't in Sarah's case because of the subcutaneous edema she had in her neck.