In severe tricuspid regurgitation (TR), the regurgitant jet flows back from the right ventricle into the right atrium during systole, causing reversal of flow in the hepatic veins during the same phase. On Doppler echocardiography, this manifests as systolic flow reversal in the hepatic veins, which is a hallmark sign of severe TR.
Normally, hepatic vein flow consists of a predominant systolic forward flow into the right atrium. However, in severe TR, the high pressure in the right atrium during systole causes retrograde flow in the hepatic veins. This pattern is diagnostic and aids in severity assessment.
Diastolic flow reversal is uncommon in TR and more associated with other pathologies. Atrial flow reversal in systole or biphasic flow reversal in diastole are not recognized patterns for severe TR.
This is described in detail in the "Textbook of Clinical Echocardiography, 6e", Chapter on Right Heart and Tricuspid Valve Disease, with Doppler patterns illustrated for hepatic vein flow in tricuspid regurgitation【20:330-335†Textbook of Clinical Echocardiography】.
