Real-time phase-contrast flow MRI of haemodynamic changes in the ascending aorta and superior vena cava during Mueller manoeuvre

Abstract

AIM: To evaluate the potential of real-time phase-contrast flow magnetic resonance imaging (MRI) at 40 ms resolution for the simultaneous determination of blood flow in the ascending aorta (AA) and superior vena cava (SVC) in response to reduced intrathoracic pressure (Mueller manoeuvre).MATERIALS AND METHODS: Through-plane flow was assessed in 20 healthy young subjects using real-time phase-contrast MRI based on highly undersampled radial fast low-angle shot (FLASH) with image reconstruction by regularized non-linear inversion. Haemodynamic alterations (three repetitions per subject ¼ 60 events) were evaluated during normal breathing (10 s), inhalation with nearly closed epiglottis (10 s), and recovery (20 s).RESULTS: Relative to normal breathing and despite interindividual differences, reduced intrathoracic pressure by at least 30 mmHg significantly decreased the initial peak mean velocity (averaged across the lumen) in the AA by À24 AE 9% and increased the velocity in the SVC by þ28 AE 25% (p < 0.0001, n ¼ 23 successful events). Respective changes in flow volume per heartbeat were À25 AE 9% in the AA and þ49 AE 44% in the SVC (p < 0.0001, n ¼ 23). Flow parameters returned to baseline during sustained pressure reduction, while the heart rate was elevated by 10% (p < 0.0001) after the start (n ¼ 24) and end (n ¼ 17) of the manoeuvre. CONCLUSIONS: Real-time flow MRI during low intrathoracic pressure non-invasively revealed quantitative haemodynamic adjustments in both the AA and SVC.

Suction/Inspiration against resistance or standardized Mueller maneuver : a new breathing technique to improve contrast density within the pulmonary artery: a pilot CT study

“…As described graphically in Fig. 6 (and Video 1, supplementary material), suction against resistance exerts a specific physiological influence on the flow ratios of the superior und inferior vena cava, as described recently [14,19]. First, during normal inspiration without any resistance, the diaphragm moves caudally.…”

Aortic Pulse Wave Velocities Using Real-Time Phase-Contrast MRI

“…However, when analyzing the distance for specific breathing conditions (i.e., during breathhold after inhalation or exhalation), the differences between two locations in the ascending and descending aorta (same section) turned out to be surprisingly small (about 3%, data not shown) and unable to account for the PWV modulations during free breathing. The latter effect has to be ascribed to the lowered intrathoracic pressure during inspiration which causes increased flow velocities in the ascending aorta [35].…”

“…real-time PC MRI will allow for studying PWV variations in response to breathing maneuvers [27,35,36] or protocols of physical exercise which may aid in the diagnosis of patients with suspected aortic stiffness. Fig.…”

“…This situation may now be overcome by recent advances in real-time MRI which combine highly undersampled radial fast low-angle shot (FLASH) acquisitions with image reconstructions by regularized nonlinear inversion (NLINV) [28][29][30][31][32]. This technique has been adapted to PC MRI to obtain flow information in real time [33][34][35][36]. The aim of this study was to evaluate the performance and potential of PWV determinations based on real-time PC MRI in comparison to conventional cine PC MRI.…”

W(h)ither human cardiac and body magnetic resonance at ultrahigh fields? technical advances, practical considerations, applications, and clinical opportunities

“…cardiac arrhythmias) constraints, which might cause inappropriate diagnostic information. Free breathing real time cardiac MRI achieves diagnostic quality in a single heartbeat and bears the potential to change the landscape of cardiac diagnostics . These developments will afford an improved clinical accuracy and efficacy of CMR.…”