Noninvasive estimation of pulmonary vascular resistance in pulmonary hypertension

Background: Determination of pulmonary vascular resistance (PVR) in patients with suspected or known pulmonary hypertension (PH) requires right heart catheterization. Our purpose was to use Doppler echocardiography to estimate PVR in patients with PH. Methods: Patient population consisted of 52 patients (53 ± 12 years; 35 females) who underwent Doppler echocardiography and right heart catheterization within 24 hours of each other. The ratio of peak tricuspid regurgitation velocity (TRV) and right ventricular outflow time-velocity integral (VTI _RVOT) was measured via transthoracic echocardiography and correlated to invasively determined PVR. A linear regression equation was generated to determine PVR by echocardiography based upon the TRV-VTI _RVOT ratio. PVR by echocardiography was compared to invasive PVR using Bland-Altman analysis. Results: Significant correlation was demonstrated between TRV-VTI _RVOT and PVR by catheterization (r = 0.73; P < 0.001). However, Bland-Altman analysis showed that agreement between PVR determined by echocardiography and invasive PVR was poor (bias = 0; standard deviation = 4.3 Wood units). In a subset of patients with invasive PVR < 8 Wood units (26 patients), correlation between TRV-VTI _RVOT and invasive PVR was strong (r = 0.94; P < 0.001). In these patients, agreement between PVR by echocardiography and invasive PVR was satisfactory (bias = 0; standard deviation = 0.5 Wood units). There was no correlation between TRV-VTI _RVOT and invasive PVR in patients with PVR > 8 Wood units (n = 26; r = 0.17). Conclusion: While TRV-VTI _RVOT correlates significantly with PVR, using it to estimate PVR in a PH patient population cannot be recommended.