Noninvasive Estimation of Pulmonary Vascular Resistance Using Right Ventricular Outflow Doppler Analysis

Right heart catheterization (RHC) is the gold standard for measuring pulmonary vascular resistance (PVR). Current noninvasive methods lack accuracy, especially in moderate to severe pulmonary arterial hypertension.

The objective of the study was to develop and validate a novel echocardiographic method for estimating PVR using right ventricular outflow tract Doppler notch analysis.

In this prospective study, of 95 patients undergoing RHC, 35 with isolated postcapillary pulmonary hypertension (PVR <2.0 WU) and no discernible Doppler notches were excluded. Of the remaining, 54 patients with interpretable Dopplers were divided into derivation (n = 30) and validation (n = 24) cohorts, all undergoing invasive PVR (iPVR) measurement and echocardiography within 24 hours. Right ventricular outflow tract Doppler, specifically the ratio of notch time (NT) to ejection time, was analyzed to derive a regression equation for non-invasive PVR (niPVR). The model was validated against iPVR and compared with 5 existing methods.

Stepwise linear regression identified the inverse of NT as the strongest predictor of iPVR. After adjusting for heart rate, the model (R² = 0.93) yielded non-iPVR = 7.1∗(ejection time/NT) - 9.36. Validation against 5 established methods showed superior performance across a PVR range of 2.3 to 14.2 WU, with the highest Pearson correlation (r: 0.76; P < 0.0001; 95% CI: 0.52-0.89). Bland-Altman analysis confirmed superior agreement.

This novel echocardiographic method offers feasible, rapid, reliable PVR estimation with strong correlation to invasive measurements. Although not a substitute for RHC, this promising preliminary finding from a selective cohort may aid in identifying candidates for invasive testing and guide pulmonary hypertension management. Larger, multicenter validation is warranted.