A feasible method for non-invasive measurement of pulmonary vascular resistance in pulmonary arterial hypertension: Combined use of transthoracic Doppler-echocardiography and cardiac magnetic resonance. Non-invasive estimation of pulmonary vascular resistance

BACKGROUND: Transthoracic Doppler-echocardiography (TTE) can estimate mean pulmonary arterial pressure (MPAP) and pulmonary capillary wedge pressure (PCWP) reliably, and cardiac magnetic resonance (CMR) is the best modality for non-invasive measurement of cardiac output (CO). We speculated that the combined use of TTE and CMR could provide a feasible method for non-invasive measurement of pulmonary vascular resistance (PVR) in pulmonary arterial hypertension (PAH). METHODS AND RESULTS: Right heart catheterization (RHC) was undertaken in 77 patients (17M/60F) with PAH, and simultaneous TTE was carried out to evaluate MPAP, PCWP and CO. Within 2 days, CO was measured again with CMR in similar physiological status. Then, PVR was calculated with the integrated non-invasive method: TTE-derived (MPAP–PCWP)/CMR-derived CO and the isolated TTE method: TTE-derived (MPAP–PCWP)/TTE-derived CO, respectively. The PVR calculated with integrated non-invasive method correlated well with RHC-calculated PVR (r = 0.931, 95% confidence interval 0.893 to 0.956). Between the integrated non-invasive PVR and RHC-calculated PVR, the Bland–Altman analysis showed the satisfactory limits of agreement (mean value: − 0.89 ± 2.59). In comparison, the limits of agreement were less satisfactory between TTE-calculated PVR and RHC-calculated PVR (mean value: − 1.80 ± 3.33). Furthermore, there were excellent intra- and inter-observer correlations for the measurements of TTE and CMR (P < 0.001 for all). CONCLUSIONS: The combined use of TTE and CMR provides a clinically reliable method to determine PVR non-invasively. In comparison with RHC, the integrated method shows good accuracy and repeatability, which suggests the potential for the evaluation and serial follow-up in patients with PAH. TRANSLATIONAL PERSPECTIVE: In PAH, the non-invasive measurement of PVR is very important in clinical practice. Up to now, however, the widely accepted non-invasive method is still unavailable. Since TTE can estimate (MPAP–PCWP) reliably and CMR is the best image modality for the measurement of CO, the combined use of two modalities has the potential to determine PVR non-invasively. In this research, the integrated non-invasive method showed good diagnostic accuracy and repeatability compared with RHC. Therefore, it might be a feasible method for non-invasive measurement of PVR in patients with PAH.