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Multicenter Study
. 2019 Apr;32(2):269-279.
doi: 10.1007/s10334-018-0702-z. Epub 2018 Aug 31.

Evaluation of atrial septal defects with 4D flow MRI-multilevel and inter-reader reproducibility for quantification of shunt severity

Raluca G Chelu  1   2 , Michael Horowitz  3 , Dominica Sucha  4 , Isabella Kardys  5 , Delphine Ingremeau  6 , Shreyas Vasanawala  7 , Koen Nieman  8   9   7   10 , Jean-Francois Paul  6 , Albert Hsiao  3
Affiliations
Multicenter Study

Evaluation of atrial septal defects with 4D flow MRI-multilevel and inter-reader reproducibility for quantification of shunt severity

Raluca G Chelu et al. MAGMA. 2019 Apr.

Abstract

Purpose: With the hypothesis that 4D flow can be used in evaluation of cardiac shunts, we seek to evaluate the multilevel and interreader reproducibility of measurements of the blood flow, shunt fraction and shunt volume in patients with atrial septum defect (ASD) in practice at multiple clinical sites.

Materials and methods: Four-dimensional flow MRI examinations were performed at four institutions across Europe and the US. Twenty-nine patients (mean age, 43 years; 11 male) were included in the study. Flow measurements were performed at three levels (valve, main artery and periphery) in both the pulmonary and systemic circulation by two independent readers and compared against stroke volumes from 4D flow anatomic data. Further, the shunt ratio (Qp/Qs) was calculated. Additionally, shunt volume was quantified at the atrial level by tracking the atrial septum.

Results: Measurements of the pulmonary blood flow at multiple levels correlate well whether measuring at the valve, main pulmonary artery or branch pulmonary arteries (r = 0.885-0.886). Measurements of the systemic blood flow show excellent correlation, whether measuring at the valve, ascending aorta or sum of flow from the superior vena cava (SVC) and descending aorta (r = 0.974-0.991). Intraclass agreement between the two observers for the flow measurements varies between 0.96 and 0.99. Compared with stroke volume, pulmonic flow is underestimated with 0.26 l/min at the main pulmonary artery level, and systemic flow is overestimated with 0.16 l/min at the ascending aorta level. Direct measurements of ASD flow are feasible in 20 of 29 (69%) patients.

Conclusion: Blood flow and shunt quantification measured at multiple levels and performed by different readers are reproducible and consistent with 4D flow MRI.

Keywords: 4D flow MRI; Atrial septal defect; Multiple measurements.

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Conflict of interest statement

Conflict of interest

R.G. Chelu received funding for research from GE Healthcare and is a consultant to Arterys, Inc. J.W. Roos-Hesellink received a grant from the Dutch Heart Foundation. K. Nieman reports non-financial support from Siemens Medical Solutions and grants from GE Healthcare and Bayer Healthcare, outside the submitted work. S.S. Vasanawala is involved in research collaboration with GE Healthcare, is founder of and consultant to Arterys, Inc., and received a research grant from Bayer AG. A. Hsiao is founder of and consultant to Arterys, Inc., and received a research grant from GE Healthcare. The rest of the authors report no conflict of interest.

Ethical standards

Patient studies were aggregated from multiple centers and approved by each local IRB, including either a waiver of consent or prospective enrollment with signed consent, as deemed appropriate by each center. The study protocol was compliant with the Declaration of Helsinki.

Figures

Fig. 1
Fig. 1
Multiple rendering techniques for ASD visualization. Color velocity overlay helps to identify the shunt in a frame-by-frame approach, but does not show flow directionality a. Flow direction is emphasized with vector overlay b. Streamlines help to track the flow that comes from pulmonary veins to the left atrium. In case of an atrial septum defect, the blood will cross to the right atrium and right ventricle. Ra right atrium, rv right ventricle, la left atrium, lv left ventricle, SVC superior vena cava
Fig. 2
Fig. 2
Levels of flow and shunt measurement. Systemic a and pulmonic b blood flows were measured at three different levels. Systemic flow a was measured at the aortic valve level [1], ascending aorta level [2] and as sum (3 = 3a + 3b) of the flow of the superior vena cava above the azygos vein (3a) and descending aorta (3b). When present, left persistent superior vena cava flow was added to the sum of SVC and descending aorta. Pulmonic flow b was measured at the pulmonary valve level [1], main pulmonary artery level [2] and as the sum of the right (3a) and left pulmonary artery flow (3b). Ventricular stroke volumes were calculated using magnitude images c. Additionally, shunt volumes were measured at the ASD level by septal tracking d
Fig. 3
Fig. 3
Pulmonary flow. Correlation and Bland-Altman plots of pulmonic flow measured at different levels using as reference the level of the main pulmonary artery. For each Bland-Altman plot, the average of measurements from both levels is plotted on the x-axis and the difference is plotted on the y-axis. The solid gray horizontal line plots the mean difference, and the dotted gray lines indicate the limits of agreement. PV pulmonary valve, MPA main pulmonary artery, RPA right pulmonary artery, LPA left pulmonary artery
Fig. 4
Fig. 4
Systemic flow. Correlation and Bland-Altman plots of systemic flow measurements at different levels and taking as reference the level of the ascending aorta. For each Bland-Altman plot, the average of measurements from both levels is plotted on the x-axis and the difference is plotted on the y-axis. The solid gray horizontal line plots the mean difference, and the dotted gray lines indicate the limits of agreement. AV aortic valve, AoAsc ascending aorta, AoD descending aorta, SVC superior vena cava
Fig. 5
Fig. 5
Distribution of atrial septal defect shunt fractions (Qp/Qs) measured at multiple levels. Qp/Qs at different locations ordered from high to low. A solid line is placed at the treatment threshold of 1.5 Qp/Qs. Arrows highlight the three patients in which the measurements at different levels are crossing the threshold line
See this image and copyright information in PMC

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