Background: Pulmonary vascular resistance (PVR) is an important measurement for the diagnosis and the follow up of patients with pulmonary hypertension (PH) but needs accurate determination of mean pulmonary artery pressure (PAMP). A number of methods using Doppler echocardiography has been proposed to estimate PVR but with limited accuracy. We aimed to test the accuracy of a new measurement of PVR using the conventional invasive equation.Methods: We investigated 30 patients undergoing right heart catherization (RHC), mean age 62±13 year, 21 females, with different diseases; idiopathic pulmonary arterial hypertension (PAH) (n=5), associated PAH (n=15), chronic thromboembolic PH (n=6), interstitial lung disease (n=2), and after closure of an atrial septal defect (n=1). Patients with impaired LV systolic function (EF <50%) or elevated pulmonary capillary wedge pressure (>15 mmHg on RHC) were excluded. We used the formula; PAMP = PASP echo x 0.61+2 mmHg where PASP echo= peak tricuspid regurgitation pressure drop + 10mm Hg. PVR was then calculated as PAMP echo-PCWP/cardiac output. PCWP was estimated at 10 mmHg in all cases. We compared this method with previously presented methods of estimating PVR.Results: Doppler estimation of PVR echo was achievable in 90% of patients in whom calculation of PAMP was obtainable. PVR echo strongly correlated with those from RHC (r=0.85, p<0.001). The regression equation was PVR rhc=0.95 × PVR echo -0.29, and the regression line was close to identity. Bland Altman plot showed a good agreement between PVR echo and PVR rhc values with a mean difference of -0.66 ± 2.1 WU, fig 1A and B.Conclusion: The proposed Doppler derived formula for estimating PVR based on conventionally used invasive equation strongly correlates with invasive gold standard measures.