Flow Volume and Shunt Quantification in Pediatric Congenital Heart Disease by Real-Time Magnetic Resonance Velocity Mapping

Abstract

Background-Flow quantification in real time by phase-contrast MRI (PC-MRI) may provide unique hemodynamic information in congenital heart disease, but available techniques have important limitations. We sought to validate a novel real-time magnetic resonance flow sequence in children. Methods and Results-In 14 pediatric patients (mean age 5.2Ϯ2.0 years) with cardiac left-to-right shunt, pulmonary (Q p ) and aortic (Q s ) flow rates were determined by nontriggered free-breathing real-time PC-MRI with single-shot echo-planar imaging combined with sensitivity encoding, which yielded 25 phase images per second at 2.7ϫ2.7-mm in-plane resolution (field of view 30ϫ34 cm 2 ). Over a 9.5-second period that included 2 to 5 respiratory cycles, 16.6Ϯ2.6 subsequent stroke volumes (range 13 to 22) were acquired in each vessel. Results were compared with conventional retrospectively ECG-gated PC-MRI. Mean Q p /Q s by conventional PC-MRI was 1.91Ϯ0.64, and it was 1.94Ϯ0.68 (meanϮSD) by real-time PC-MRI. For blood flow rate through pulmonary artery and aorta, we found differences of 2% to 3% (Bland-Altman analysis), with lower limits of agreement of Ϫ11% to Ϫ13% (meanϪ2 SD) and upper limits of 18% to 19% (meanϩ2 SD), which demonstrated good agreement between both methods. Mean difference for Q p /Q s was 1%, with limits of agreement ranging between Ϫ18% and 22% (meanϮ2 SD). High repeatability but some flow overestimation was observed in vitro (pulsatile flow phantom) with real-time PC-MRI, whereas conventional PC-MRI was accurate. Beat-to-beat stroke-volume variation was 6.1Ϯ2.3% in vivo and 3.7Ϯ0.3% in vitro. Conclusions-Beat-to-beat quantification of pulmonary and aortic flows and hence left-to-right shunt within a few seconds is reliable by nontriggered real-time PC-MRI with echo-planar imaging and sensitivity encoding. Good spatial/temporal resolution and a large field of view may render the sequence valuable for multiple applications in congenital heart disease.

Phase‐contrast magnetic resonance quantification of normal pulmonary venous return

“…Nevertheless, the differences are within 5%, which is a reasonable error range for PCMR flow measurement. The small intra-and interobserver differences for pulmonary venous return may be attributable to the higher temporal resolution and greater level of excitation used in our study than in previous studies (2)(3)(4)(5)(6).…”

“…Phasecontrast MR imaging (PCMR) has been validated as accurate in evaluating velocity, volume, and pattern of pulsatile blood flow (1)(2)(3)(4)(5). Flow measurements using PCMR have been used at various great vessels, including the aorta, the pulmonary artery, and the superior and inferior vena cavae, in various clinical settings (6 -10).…”

Assessment of Pulmonary Arterial Pressure by Velocity-Encoded Cine Magnetic Resonance Imaging in Children With Congenital Heart Disease

“…For flow measurements in neonates, the child should weigh approximately 3 kg or more, and the duration of 1 heartbeat should not be less than 600 ms. Sedation is required to protect children against the loud noise emitted by the MRI equipment, but caution in interpreting the resultant data is needed because deep sedation can result in a decrease in the systemic blood pressure or respiratory rate; therefore, the hemodynamics may not necessarily be identical to those of daily life. 30 …”

Cardiovascular Magnetic Resonance

“…Atrial septal defect is well visualized with echocardiography, but CMR may be useful in older patients or those with limited acoustic windows and is preferable for quantifying the shunt 28 and the effects on RV function. The position of the atrial septal defect relative to the atrioventricular valve and pulmonary veins can be established, and associated pulmonary venous anomalies can be shown.…”