Echocardiographic Estimation of Pulmonary Vascular Resistance in Chronic Thromboembolic Pulmonary Hypertension: Utility of Right Heart Doppler Measurements

The ratio of tricuspid regurgitation velocity divided by the velocity‐time integral of right ventricular outflow tract pulsed‐wave Doppler tracing (TRV/VTI_RVOT) has been used to estimate pulmonary vascular resistance (PVR). However, this method has not been validated in chronic thromboembolic pulmonary hypertension (CTEPH). We assessed the utility of TRV/VTI_RVOT in patients with CTEPH and PVR from 2 to 20 WU. All had right heart catheterization (RHC) within 2 days of echocardiography. TRV/VTI_RVOT was calculated and RHC‐derived pressures, PVR, and cardiac outputs were recorded. Mean pulmonary artery pressure was 47 ± 12 mmHg, cardiac output: 4.2 ± 1.1 L/min, PVR: 9 ± 4 WU, right atrial pressure: 12 ± 6 mmHg. Mean VTI_RVOT was 13 ± 5 cm; mean TRV was 4.2 ± 0.8 m/s, mean tricuspid regurgitation severity was 2.5 ± 0.8 (1 = trace, 2 = mild, 3 = moderate, 4 = severe). Regression analysis demonstrated a correlation between RHC PVR and TRV/VTI_RVOT: PVR = 19.4 × (TRV/VTI_RVOT) + 2.4 (r = 0.74, P < 0.001). However, Bland–Altman analysis found a poor degree of agreement between echo‐derived PVR and RHC PVR. We also studied 28 patients with non‐CTEPH pulmonary hypertension. Similar analysis revealed a regression equation of PVR = 20.1 × (TRV/VTI_RVOT) + 0.3 (r = 0.57, P < 0.01). Conclusion: TRV/VTI_RVOT is only marginally useful for estimating PVR in CTEPH (r = 0.74). Moreover, the regression equation in CTEPH differs significantly from previous studies in pulmonary hypertension. Reasons for this may include the markedly elevated PVR levels in this population and specific effects on VTI_RVOT from CTEPH.