Determinants of Right Heart Hemodynamic Derangement in Patients With and Without Tricuspid Regurgitation

Background: The determinants of tricuspid regurgitation (TR) hemodynamic severity remain to be established. We explored the hemodynamic correlates of right atrial (RA) pressure and stroke volume (SV) in patients with and without TR, and assessed the reliability of the indirect Fick method in relation to TR severity. Methods: In this observational study, right ventricular (RV) 3-dimensional echocardiography (3DE) was obtained simultaneously with direct Fick right heart catheterization. RVSV3DE and SVRHC were combined to determine the TR regurgitant fraction (RegFr=RVSV3DE-RVSVRHC/RVSV3DE). RA pressures and strain (or 3DE volumes) were combined to derive RA compliance. Results: Out of 74 patients, 61% had moderate or severe TR. TR severity was associated with larger right heart chambers, lower RA compliance, higher values and lower inspiratory decrease of RA pressure, and lower cardiac index (P<0.01). In univariate analysis, RA V wave was associated with RegFr (r=-0.57) and with ln-transformed RA compliancestrain (r=-0.74); SV index was associated with RegFr (r=-0.65). The effect of RegFr on V wave was mediated by ln-transformed RA compliancestrain (β, 13.9 [95% CI, 7.6-20.2]). In multivariable analysis, RA V wave remained associated with 1/RA compliancestrain (β, 2.1 [95% CI, 1.4-2.7]), while SV index was associated with RegFr (β, -97.6 [95% CI, -120.1 to -75.0]). The indirect Fick method overestimated cardiac index proportionally to RegFr (P<0.01). Conclusions: SV index is related to TR severity, while the effect of TR on RA V wave is mediated by RA compliance. Respiratory-related changes in RA hemodynamics are associated with TR severity. The indirect Fick method overestimates cardiac index proportionally to TR severity.