Reliability of Doppler echocardiography in the assessment of high pulmonary vascular resistance in patients with severe pulmonary arterial hypertension

BACKGROUND: The objective is to assess whether the squaring of tricuspid regurgitation velocity (TRV) gives an improved estimate of pulmonary vascular resistance (PVR) or is equivalent to the ratio of TRV and time velocity integral of right ventricular outflow tract (TVI(RVOT)) (TRV/TVI(RVOT)) for assessing PVR in patients with high PVR values. METHODS: Thirty patients predicted to have PVR >6 WU by Doppler were included in the present study. TRV and TVI(RVOT) were measured by echo Doppler. TRV/TVI(RVOT) and TRV(2)/TVI(RVOT) were calculated. PVR(CATH) was estimated within 2 h of Doppler study. Regression equations for calculating PVR from TRV/TVI(RVOT) (PVR(ECHO1)) and TRV(2)/TVI(RVOT) (PVR(ECHO2)) were developed. Bland–Altman analysis for agreement between PVR(CATH) and PVR(ECHO1), PVR(ECHO2) was carried out. RESULTS: The mean value of PVR(CATH) was found to be 15.08 ± 7.03 WU. The calculated values of PVR(ECHO1) and PVR(ECHO2) were found to be 15.08 ± 6.34 WU and 15.05 ± 6.08 WU, respectively. The linear regression analysis carried out for PVR(CATH) and TRV/TVI(RVOT) showed good correlation (R = 0.84). Bland–Altman analysis showed excellent agreement between the two Doppler methods and invasive PVR with negligible bias. CONCLUSION: Noninvasive estimation of PVR by Doppler is reliable even in patients with high PVR (>6 WU) and, squaring TRV is not superior to TRV alone.