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Abstract

Patient-Specific Analysis of Aortic Hemodynamics and Wall Shear Stresses in Patients Undergoing Pediatric Bariatric Surgery using 2D Phase-Contrast MRI

Feranmi Akande1 Nathan Hargan2 Haesung Kang3 David Lanning3 Uyen Truong4 João S. Soares1

1 Department of Biomedical Engineering, College of Engineering, Virginia Commonwealth University

2 Department of Mechanical & Nuclear Engineering, College of Engineering, Virginia Commonwealth University

3 Department of Cardiology, Children’s Hospital of Richmond, Virginia Commonwealth University

Introduction: Severe obesity among today’s youth is a rising epidemic within the United States. Emerging research has linked childhood obesity with shortened life expectancy and early adverse cardiovascular effects, including increased aortic stiffness. Bariatric surgery is an effective and safe option for weight loss in severely obese pediatric patients when behavioral and nutritional approaches prove ineffective [1]. MRI data can provide hemodynamic insight into maladaptive changes in the aorta. This study focuses on examining the wall shear stress (WSS) and hemodynamic changes detected by MRI in bariatric patients before and 6 months after bariatric surgery. WSS is an independent predictor of all causes of cardiovascular mortality.

Materials and Methods: Five PCMRI datasets were collected from pediatric patients before and after bariatric surgery. Each dataset consisted of time-resolved 2D cross-sections of the thoracic aorta. Time step segmentation masks for 2D planes of the aorta were generated utilizing ImageJ software. Segmentations were done independently by one observer and reviewed by a code generated PCMRI mask checker. Jupyter Notebook Python custom codes were developed to allow for loading and processing of the PCMRI data, as well as filtering and correcting of masking and timestep offset errors. In addition, the codes were used to generate hemodynamic results and estimate wall shear stress in 4 regions of the aorta over the entire cardiac cycle.

Results: Subjects’ mean age was 15±3 years. Various hemodynamic metrics such as stroke volume, aortic luminal area, peak flow rate and retrograde flow, and wall shear stress were computed. Visual representations included flow-rate, area, blood volume, and velocity versus time charts, 2D colormaps of velocity profiles, wall shear averages, and wall shear distribution. Clinically relevant factors such as cardiac output and ejection time were also calculated. Although resting heart rate (HR) was within normal ranges before surgery, a decrease in HR was observed post-surgery which can potentially be attributed to the drastic decrease in weight. A decrease in cardiac output, as well as stroke volume, was observed due to the decrease in HR and weight for each patient. For the majority of the cases, observable differences in the maximum and minimum WSS were noticeable pre- vs. post-surgery, despite there being very small differences in the velocity profiles and peak maximum and minimum velocities.

Conclusions: 2D-PCMRI can provide key information on hemodynamic changes in patients before and after bariatric surgery. Additionally, 2D visualizations and animations of velocity contours and gradients can provide additional insights into the flow patterns and estimation of WSS. More data and analysis are needed in order to confidently validate statistical findings.

Acknowledgments: VCU College of Engineering Dean’s Undergraduate Research Initiative 2022, Children’s Hospital of Richmond. VCU CTSA Pilot Project Award, 2021.

Publication Date

2023

Subject Major(s)

Biomedical Engineering, Medicine, Mechanical Engineering

Keywords

Pediatrics, Cardiology, Bariatric Surgery, MRI Analysis, Aortic Hemodynamics and Wall Shear Stress

Disciplines

Bioimaging and Biomedical Optics | Biomedical Engineering and Bioengineering | Cardiology | Endocrinology, Diabetes, and Metabolism | Gastroenterology | Mechanical Engineering | Pediatrics | Surgery

Current Academic Year

Senior

Faculty Advisor/Mentor

Joao Soares

Rights

© The Author(s)

Recommended Citation

References: [1] Armstrong et al., Pediatric metabolic and bariatric surgery: Evidence, barriers, and best practices. Pediatrics (2019) 144(6):e20193223, https://doi.org/10.1542/peds.2019-3223

Patient-Specific Analysis of Aortic Hemodynamics and Wall Shear Stresses in Patients Undergoing Pediatric Bariatric Surgery using 2D Phase-Contrast MRI

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