Right Ventricular–Pulmonary Artery Uncoupling in Secondary Tricuspid Regurgitation: Invasive Validation of Echocardiographic Surrogates

BACKGROUND: Assessment of right ventricular (RV) function can be challenging in patients with RV volume overload associated with secondary tricuspid regurgitation and heart failure with preserved ejection fraction. We sought to validate echocardiographic metrics that might serve as noninvasive RV-pulmonary artery (PA) coupling surrogates. METHODS: Invasive RV pressure-volume loops were obtained in 16 patients with heart failure, preserved ejection fraction, and at least moderate secondary tricuspid regurgitation. Right ventricular end-systolic elastance (Ees), effective arterial elastance (Ea), tricuspid regurgitation-adjusted Ea (Epa), and related RV-PA coupling indices (Ees/Ea, Ees/Epa) were derived. We explored correlations between RV-PA coupling, hemodynamics, and conventional and 3-dimensional echocardiographic metrics, including forward stroke volume/RV end-systolic volume ratio, effective RV ejection fraction, tricuspid regurgitant volume, and regurgitant fraction. RESULTS: Right ventricularejection fraction was 61% ± 10%, tricuspid regurgitant volume was 42 (23-59) mL, and regurgitant fraction was 40% ± 19%. The Ea underestimated RV afterload, and Ees/Ea overestimated RV-PA coupling compared with Ees/Epa (0.64 ± 0.24 vs 0.44 ± 0.23, P < .001). The value of Ees/Ea correlated with RV ejection fraction (r = 0.59; P = .017; 95% CI, 0.00, 0.85). The value of Ees/Epa correlated with forward stroke volume/RV end-systolic volume (ρ = 0.76; P < .001; 95% CI, 0.37, 0.95), effective RV ejection fraction (r = 0.80; P < .001; 95% CI, 0.54, 0.94), regurgitant volume (r = -0.67; P = .004; 95% CI, -0.90, -0.57), and regurgitant fraction (r = -0.77; P < .001; 95% CI, -0.91, -0.50). Conversely, the ratio between tricuspid annular plane systolic excursion and PA systolic pressure was not correlated with either Ees/Ea (r = 0.03, P = .91) or Ees/Epa (r = -0.02, P = .93). CONCLUSIONS: In our small cohort of patients with tricuspid regurgitation secondary to heart failure with preserved ejection fraction, RV-PA uncoupling was frequent, underestimated by tricuspid regurgitation-unadjusted metrics, and associated with more impaired hemodynamics. Three-dimensional echocardiography-derived forward stroke volume/RV end-systolic volume, effective RV ejection fraction, tricuspid regurgitant volume, and regurgitant fraction were associated with Ees/Epa, while tricuspid annular plane systolic excursion/PA systolic pressure was not.