11.1 Tricuspid Regurgitation Mechanism and Severity
Key Takeaways
- TR may be primary, ventricular functional, atrial functional, device related, or mixed; mechanism requires multiplane anatomy and remodeling assessment.
- A lead is causal only when direct leaflet or subvalvular interference is demonstrated rather than inferred from its presence across the valve.
- Severity integrates color, vena contracta, flow convergence, CW, hepatic-vein flow, quantitative measures, RA/RV response, and systemic venous findings.
- Respiration, rhythm, volume status, ventilation, RV afterload, and pressure equalization can change TR appearance and must accompany serial or severity conclusions.
Define the mechanism before grading the jet
Tricuspid regurgitation, or TR, is systolic flow from RV to RA through failed leaflet coaptation. A complete examination identifies the lesion, the remodeling that produced it, and its hemodynamic consequences. Use parasternal RV inflow, RV-focused apical, subcostal, and short-axis sweeps; add 3-D imaging when feasible. The tricuspid valve usually has anterior, septal, and posterior leaflets, but leaflet number and arrangement vary, so one 2-D plane cannot prove the entire anatomy.
| Mechanism | Structural process | Typical clues |
|---|---|---|
| Primary TR | Intrinsic leaflet, chordal, papillary, or annular disease | Prolapse or flail, endocarditis, perforation, trauma, carcinoid restriction, rheumatic disease, congenital abnormality |
| Ventricular functional TR | RV pressure or volume overload dilates and distorts the annulus and displaces papillary muscles | RV enlargement, annular dilation, apical tethering, reduced coaptation, PH or LV disease |
| Atrial functional TR | Long-standing atrial remodeling enlarges RA and annulus with relatively little tethering | AF, marked RA enlargement, basal RV conical dilation, coaptation near the annular plane |
| Device-related TR | A lead directly alters leaflet or subvalvular motion | Impingement, adherence, entanglement, perforation, or interference with coaptation |
A lead crossing the valve is device associated, not automatically device related. Demonstrate direct interaction in two orthogonal planes or 3-D, identify the affected leaflet, and show whether the lead prevents closure throughout systole. Compare preimplant images when available. A lead may be an innocent bystander in functional TR, while annular dilation and tethering are the true mechanism. Conversely, shadowing can hide impingement. Record lead trajectory, leaflet mobility, coaptation gap, annular size, and other mechanisms rather than assigning causality from proximity.
Functional TR is dynamic. RV afterload, volume status, diuresis, positive-pressure ventilation, and rhythm alter annular geometry and the RV-RA pressure difference. Severe pulmonary hypertension does not guarantee severe TR, and severe TR can occur without severe pulmonary hypertension. Record blood pressure, rhythm, oxygen or ventilation state, and relevant treatment. Compare serial studies under similar loading when possible.
Acquire complementary severity evidence
Optimize color scale, gain, depth, and sector width, then sweep through the entire coaptation line. Evaluate flow convergence, vena contracta, jet direction, area, and systolic duration. Eccentric wall-hugging jets can appear small; very wide-open TR may have such a low velocity that aliasing is limited and the jet loses a dramatic mosaic appearance. Measure vena contracta perpendicular to flow from more than one view and avoid a blooming or poorly resolved neck. Multiple orifices and irregular geometry reduce the meaning of one width.
Use CW Doppler from every window that aligns with the jet and save the densest complete envelope. A dense, early-peaking triangular signal supports rapid RV-RA pressure equalization, but signal shape alone is not a grade. A low peak velocity can occur in severe free TR, while a high velocity primarily reflects a large pressure difference. Do not infer regurgitant volume from velocity. For RV systolic pressure, an incomplete or misaligned envelope underestimates the gradient, and advanced TR can make both the Bernoulli gradient and RA-pressure estimate uncertain.
Obtain hepatic-vein PW Doppler with attention to respiration. Systolic flow reversal supports severe TR, but AF, pacing, elevated RA pressure, and sampling conditions can alter the pattern. Record through quiet respiration and note positive-pressure ventilation. IVC size and collapse support RA-pressure assessment in spontaneously breathing patients; standard sniff rules do not transfer uncritically to mechanical ventilation. Assess RA and RV size, RV-focused FAC, TAPSE, tissue Doppler s′, RV strain when available, septal shape, and systemic venous congestion. Chamber enlargement supports chronic significance but may be absent in acute severe TR.
Integrate the conventional grading markers
| Parameter | Mild pattern | Severe pattern | Limitation to test |
|---|---|---|---|
| Valve and chambers | Normal or mildly abnormal valve; RA/RV usually normal | Flail, retraction, large defect; RA/RV usually dilated | Acute severe TR may precede dilation |
| Color and flow convergence | Small central jet; little convergence | Large central or eccentric jet; large systolic convergence | Gain, Nyquist, driving pressure, wall effect |
| Vena contracta width | <0.3 cm | ≥0.7 cm | Irregular or multiple orifices; view dependence |
| PISA radius | ≤0.5 cm | >0.9 cm at the specified aliasing setting | Nonhemispheric convergence often underestimates flow |
| Hepatic-vein flow | Systolic dominance | Systolic flow reversal | Rhythm, RA pressure, respiration, pacing |
| CW TR | Faint or partial | Dense, often triangular | Shape and velocity are hemodynamic, not independent volumes |
| EROA and regurgitant volume | EROA <0.20 cm²; RVol <30 mL | EROA ≥0.40 cm²; RVol ≥45 mL | PISA geometry and dynamic/multiple jets |
These conventional thresholds separate mild, moderate, and severe TR; specialized structural programs may also use expanded grades. State the grading framework rather than mixing categories. No cutoff supersedes poor source data. PISA assumes a hemispheric convergence zone, yet the tricuspid orifice is often noncircular and its convergence flattens near the valve, causing underestimation. Quantitative values should be accepted only when radius, aliasing velocity, CW peak and VTI, and jet duration are valid.
When parameters disagree, explain the physiology and weight the strongest data. A lead-impinged leaflet, 0.9-cm vena contracta, dense triangular CW, hepatic systolic reversal, and RA/RV volume overload remain compelling even if eccentric color area is modest. Systolic reversal alone in AF with high RA pressure is less definitive. Reacquire after optimizing alignment and settings; use 3-D or TEE for unresolved mechanism and CMR when RV volumes or regurgitant burden remain uncertain. Report mechanism, grade, loading and rhythm, RV/RA response, pulmonary hemodynamic context, device interaction, and limitations.
Low velocity can coexist with severe TR
In wide-open TR, RV and RA pressures may equalize early, producing a triangular, relatively low-velocity CW signal. Peak velocity estimates pressure difference; it does not directly measure regurgitant volume.
A patient has a large coaptation gap, a 0.85-cm vena contracta, hepatic-vein systolic reversal, and a dense triangular TR signal with a surprisingly low peak velocity. What is the best interpretation?
Which actions help determine whether an intracardiac lead is causing TR? Select three.
Select all that apply