MR 4D flow-based mean pulmonary arterial pressure tracking in pulmonary hypertension

Abstract

Objectives Longitudinal hemodynamic follow-up is important in the management of pulmonary hypertension (PH). This study aimed to evaluate the potential of MR 4-dimensional (4D) flow imaging to predict changes in the mean pulmonary arterial pressure (mPAP) during serial investigations. Methods Forty-four adult patients with PH or at risk of developing PH repeatedly underwent routine right heart catheterization (RHC) and near-term MR 4D flow imaging of the main pulmonary artery. The duration of vortical blood flow along the main pulmonary artery was evaluated from MR 4D velocity fields using prototype software and converted to an MR 4D flow imaging-based mPAP estimate (mPAPMR) by a previously established model. The relationship of differences between RHC-derived baseline and follow-up mPAP values (ΔmPAP) to corresponding differences in mPAPMR (ΔmPAPMR) was analyzed by means of regression and Bland-Altman analysis; the diagnostic performance of ΔmPAPMR in predicting mPAP increases or decreases was investigated by ROC analysis. Results Areas under the curve for the prediction of mPAP increases and decreases were 0.92 and 0.93, respectively. With the natural cutoff ΔmPAPMR = 0 mmHg, mPAP increases (decreases) were predicted with an accuracy, sensitivity, and specificity of 91% (91%), 85% (89%), and 94% (92%), respectively. For patients in whom 4D flow allowed a point estimate of mPAP (mPAP > 16 mmHg), ΔmPAPMR correlated strongly with ΔmPAP (r = 0.91) and estimated ΔmPAP bias-free with a standard deviation of 5.1 mmHg. Conclusions MR 4D flow imaging allows accurate non-invasive prediction and quantification of mPAP changes in adult patients with PH or at risk of developing PH. Trial registration ClinicalTrials.gov identifier: NCT00575692 and NCT01725763 Key Points • MR 4D flow imaging allows accurate non-invasive prediction of mean pulmonary arterial pressure increases and decreases in adult patients with or at risk of developing pulmonary hypertension. • In adult patients with mean pulmonary arterial pressure > 16 mmHg, MR 4D flow imaging allows estimation of longitudinal mean pulmonary arterial pressure changes without bias with a standard deviation of 5.1 mmHg.

Clinical Application of 4D Flow MR Imaging to Pulmonary Hypertension

“…Reiter et al also reported that MR-driven mPAP, as calculated by the change in the duration of vortical flow, was correlated with the change in RHCdriven mPAP. 49 A secondary morphological change in PH, the dilation of the pulmonary arterial trunk, may have influenced the formation of vortex flow. However, in a study of normal subjects, vortical flow formation was reported to occur in approximately 3% of subjects without a history of PH.…”

Right ventricular energetic biomarkers from 4D Flow CMR are associated with exertional capacity in pulmonary arterial hypertension

“…4D flow CMR, an emerging time-resolved phasecontrast technique with flow velocities encoded simultaneously in three directions allows comprehensive measurement of blood flow dynamics in the heart and large vessels with full volumetric coverage throughout the cardiac cycle [4][5][6]. It has been applied to investigate pulmonary artery hemodynamics in patients with PAH [7][8][9][10][11][12] but studies on intracardiac blood flow are scarce. Employing 4D flow CMR, Han et al [13] demonstrated altered RV kinetic energy (KE) parameters derived from computational analysis of individual pathlines and velocities within the RV between PAH patients and controls.…”

Correlation between Pulmonary Artery Pressure and Vortex Duration Determined by 4D Flow MRI in Main Pulmonary Artery in Patients with Suspicion of Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

“…The vortex duration method was first introduced by Reiter et al who went from using a single slice with 3D velocity encoding initially [ 16 ], in order to harvest signal-to-noise-ratio by using the in-flow effect. A 4D-flow approach was used more recently by this author [ 17 , 18 ] and several other groups [ 10 , 15 ], but this technique is not currently used in clinical practice. This present work is therefore important to further validate and promote such an approach.…”

“…Several authors have already assessed the ability of cardiac MRI to detect PH and to quantify it, based on the right ventricular function and mass, the curvature of the interventricular septum [ 7 ], the flow rate across the pulmonary artery [ 8 ], the wall shear stress [ 9 , 10 ] and the presence of vortices in the pulmonary artery using 4D flow MRI [ 11 , 12 , 13 ]. In addition, it has been reported that the duration of the vortices in the pulmonary artery was related to the mPAP and could be used to detect and quantify PH [ 14 , 15 , 16 , 17 , 18 ], in patients with different causes of PH.…”