Right Atrial Waveform Changes in Tricuspid Regurgitation
In tricuspid regurgitation, the right atrial pressure waveform develops a prominent systolic wave (called a "c-V wave" or "s wave") with a blunted X descent and a prominent Y descent, reflecting the regurgitant pressure wave transmitted from the right ventricle during systole. 1, 2
Characteristic Waveform Abnormalities
Primary Changes in Severe TR
Elevated mean right atrial pressure is universally present, with the degree of elevation correlating with TR severity 2
A large systolic wave (the "s wave" or "c-V wave") replaces the normal X descent, representing the regurgitant jet forcing blood backward into the right atrium during ventricular systole 1, 3, 2
Blunted or absent X descent occurs because the normal systolic atrial relaxation is overwhelmed by the regurgitant volume entering the atrium 2
Prominent Y descent develops as the enlarged atrial volume empties rapidly into the right ventricle during early diastole 2
The Pathognomonic Finding: Ventricularization
"Ventricularization" of the right atrial pressure tracing is the most specific hemodynamic finding for severe TR, where the RA pressure contour mimics the RV pressure waveform but at lower amplitude 2
This finding indicates near-equalization of right ventricular and right atrial pressures, though it is present in only a minority of patients with severe TR 2
A truncated (notched) waveform with triangular contour and early peak velocity reflects the prominent regurgitant pressure wave transmitted into the venous system 1, 3
Doppler Correlates of Waveform Changes
Continuous Wave Doppler Characteristics
Dense triangular signal with early peaking on continuous wave Doppler corresponds to the elevated RA pressure and prominent regurgitant pressure wave seen on invasive tracings 1
The triangular contour with early peak velocity (often <2 m/s in massive TR) reflects near-equalization of RV and RA pressures 1, 3
Marked respiratory variation (decreased TR velocity with inspiration) suggests elevated RA pressure, corresponding to Kussmaul's sign on physical examination 1, 3
Hepatic Vein Flow Pattern
Systolic flow reversal in hepatic veins is the hemodynamic consequence of the elevated systolic RA pressure wave, with 80% sensitivity for severe TR 1
This can be visualized on color Doppler as retrograde flow extending into the vena cava and hepatic veins during systole 1, 3
Progressive TR severity causes a spectrum from normal systolic dominance → systolic blunting → frank systolic flow reversal 1
Important Clinical Caveats
Factors Affecting Waveform Interpretation
Blunted systolic hepatic vein flow lacks specificity because it can occur with abnormal right atrial/RV compliance, atrial fibrillation, or elevated RA pressure from any cause 1, 3
The amount of TR is influenced by multiple factors including RV preload and afterload, respiratory cycle, left heart function, and atrial fibrillation, which can alter waveform appearance 2
Absence of specific hemodynamic findings does not exclude severe TR because these findings lack sensitivity, partly due to the large effects of loading conditions and RA compliance 2
Pressure-Volume Relationships
Normal RA pressure-volume plots exhibit a figure-of-eight configuration with an "a-loop" and "v-loop" corresponding to the a-wave and v-wave 4
With severe TR, the pressure-volume plot becomes a single clockwise loop, consistent with complete ventricularization and abolition of atrial pump function 4
Intermediate degrees of TR preserve the figure-of-eight loop but increase the size of both loops, consistent with Starling-type volume loading 4