Echocardiography based estimation of pulmonary vascular resistance in patients with pulmonary hypertension: a simultaneous Doppler echocardiography and cardiac catheterization study

Aims Pulmonary vascular resistance (PVR) is an important measurement for the diagnosis of patients with pulmonary hypertension (PH) but needs accurate determination of mean pulmonary artery pressure (PAMP). We aimed to test the accuracy of a Doppler-derived measurement of PVR, using the conventional invasive equation in patients with PH. Methods and results We investigated 30 patients undergoing right heart catheterization (RHC), mean age 62 +/- 13 years, 21 females, with different diseases; idiopathic pulmonary arterial hypertension (PAH) (n = 5), associated PAH (n = 16), chronic thromboembolic PH (n = 6), interstitial lung disease (n = 2), and after closure of an atrial septal defect (n = 1). Patients with impaired left ventricular systolic function (EF < 50%) or elevated pulmonary capillary wedge pressure (PCWP >15 mmHg on RHC) were excluded. We used the formula: PAMP = PASP(echo) x 0.61 + 2 mmHg, where PASP(echo) is the peak tricuspid regurgitation pressure drop + 10 or 7 mmHg. Pulmonary vascular resistance was then calculated as PAMP(echo) - PCWP/cardiac output. Pulmonary capillary wedge pressure was estimated at 10 mmHg in all cases. The Doppler-derived estimation of PVRecho was achievable in 90% of patients, in whom accurate calculation of PAMP was obtainable. Pulmonary vascular resistance echo individual values strongly correlated with those from RHC (r = 0.85, P < 0.001 and r = 0.87, P < 0.001 for the two estimated values for right atrial pressure, respectively). The regression equation using this formula was PVRrhc = 0.95 x PVRecho - 0.29, and the regression line was close to identity. The Bland-Altman plot showed a good agreement between PVRecho and PVRrhc values, with a mean difference of -0.66 +/- 2.1 Wood unit. Conclusion The proposed Doppler-derived formula for estimating PVR based on the conventionally used invasive equation strongly correlates with invasive gold standard measures.