A 4D flow cardiovascular magnetic resonance study of flow asymmetry and haemodynamic quantity correlations in the pulmonary artery

Abstract

Objective. In this paper we elucidate the asymmetric flow pattern and the haemodynamic quantity distributions and correlations in the pulmonary artery (PA) vasculature in healthy adults having structurally normal hearts, to provide reference on the flow characteristics in the PA and the right ventricle. Approach. Velocity data are acquired non-invasively from 18 healthy volunteers by 4D flow magnetic resonance imaging, resolved to 20 phases with spatial resolution 3 × 3 × 3 mm3. Interpolation is applied to improve the accuracy in quantifying haemodynamic quantities including kinetic energy, rotational energy, helicity and energy dissipation rate. These quantities are volumetrically normalised to remove size dependency, representing densities or local intensity. Main results. Flow asymmetry in the PA is quantified in terms of all the flow dynamic quantities and their correlations. The right PA has larger diameter and higher peak stroke velocity than the left PA. It also has the highest rotational energy intensity. Counter-rotating helical streams in the main PA appear to be associated with the unidirectional helical flow noticed in the left and the right PA near the peak systole. Significance. This study provides a fundamental basis of normal flow in the PA. It implies the validity to use these flow pattern-related quantitative measures to aid with the identification of abnormal PA flow non-invasively, specifically for detecting abnormalities in the pulmonary circulation and response to therapy, where haemodynamic flow is commonly characterised by increased vortical and helical formations.

4D flow cardiovascular magnetic resonance recovery profiles following pulmonary endarterectomy in chronic thromboembolic pulmonary hypertension

“…Previous studies have shown the utility of 4D flowderived vorticity metrics which has been associated with inefficient blood flow in patients with pulmonary [12,14,15,[20][21][22][23] and aortic disease [13,16]. Although qualitative vortices and swirling has been associated with diseased states [13,22], our study shows global quantitative metrics of vorticity increasing post-PEA in patients with CTEPH.…”

“…Previous studies have shown correlations between non-invasive 4D flow CMR-derived velocity profiles and invasively measured PA pressures, as well as changes in the peak velocities after surgical correction in patients with CTEPH [4,6,[9][10][11]. Complex secondary flow structures such as vortical flow, where fluid rotates around an axis, and helical flow, where fluid rotates and moves in one direction in a cork-screw motion with clockwise (positive) or counterclockwise (negative) rotation, have been characterized with 4D flow CMRs of major vessels in healthy and diseased PAs and aortas, such as PH and bicuspid aortic valve disease [12][13][14]. Vorticity and recirculation of flow have been associated with inefficient blood flow and diseased states in the PAs and aorta [15,16].…”

“…Other methods focus on the balance between clockwise and counterclockwise helicity and normalized helicity intensity in aortic valvular disease [18,19]. 4D flow CMR in the PAs has shown promise for characterizing RV-PA dynamics in healthy subjects and patients with PH through fluid dynamics derived metrics of secondary flow profiles, such as vorticity and helicity, specifically in severe stages of PH and large dilatation of the pulmonary trunk [12,14,[20][21][22][23]. However, comprehensive analyses of velocity flow profiles and secondary flow profiles including vorticity and helicity have yet to be investigated in patients with CTEPH following a PEA to determine their utility in evaluating recovery and reverse remodeling of the RV.…”

Assessment of Pulmonary Arteries Hemodynamics and Its Relationship With Cardiac Remodeling and Myocardial Fibrosis in Athletes With Four‐Dimensional Flow MRI

“…Therefore, changes in pressure may precede changes in other hemodynamic parameters of the pulmonary artery, resulting in it being the most important indicator in early remodeling of the pulmonary circulation. Furthermore, MPA and RPA might be more susceptible to exercise compared with LPA 33 . This susceptibility may be attributed to the asymmetrical flow distribution in pulmonary arteries, as the RPA has a larger diameter, higher peak stroke velocity and higher rotational energy intensity than the LPA 22,23 .…”

“…Furthermore, MPA and RPA might be more susceptible to exercise compared with LPA. 33 This susceptibility may be attributed to the asymmetrical flow distribution in pulmonary arteries, as the RPA has a larger diameter, higher peak stroke velocity and higher rotational energy intensity than the LPA. 22,23 Consequently, RPmax of MPA-RPA was the most sensitive factor for identifying CR and/or MF, highlighting its potential importance in assessing early remodeling of the pulmonary circulation.…”