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Axel Gomez

Axel Gomez

3rd Year Medical Student
UCSF School of Medicine

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  • University of Arizona, Tucson, Arizona, B.S., Mathematics & Biochemistry, 2017
  • University of California - San Francisco, San Francisco, California, M.D., current
  • 2021
  • UCSF School of Medicine
  • Cardiothoracic surgery
  • Ascending aortic thoracic aneurysms
  • Cardiac biomechanics

Axel Gomez, B.S. is a medical student at UCSF School of Medicine. Axel Gomez received his B.S. in mathematics and biochemistry from University of Arizona in 2017. He is a member of the Cardiac Biomechanics Lab. His primary mentors are Dr. Elaine Tseng and Dr. Liang Ge. 

He started to work in the lab this past summer after finishing his first year of medical school. He used CTA images from patients with ascending aortic thoracic aneurysms (ATAA) to construct patient-specific 3D models of the aorta.

Finite element analysis, a validated computational method, is performed to obtain wall stress distributions from these models. Current ACC/AHA guidelines have a threshold diameter of >5.5 cm for elective ATAA surgical repair. Nevertheless, 59% of ATAA patients that have a dissection are found to have a diameter <5.5 cm. The lab's goal is to utilize accurate imaging based ATAA models for better rupture/dissection risk prediction. I work in all of the steps of this process including statistical analysis of the results.

Axel Gomez Presentation


Introduction: Acute type A aortic dissection is a surgical emergency that still carries high mortality. Biomechanically, dissection occurs when wall stress exceeds wall strength. Bicuspid aortic valve (BAV) disease is associated with ascending thoracic aortic aneurysms (aTAA) and BAV-aTAA carries a risk of dissection. Our aim was to examine patient-specific BAV-aTAAs to determine magnitudes of greatest wall stress by anatomic regions.

Methods: Patients with BAV-aTAA diameter >4.5cm (n=41) were recruited for the study. Patients underwent ECG-gated CT angiography (CTA) and their patient-specific 3D BAV-aTAA geometries were reconstructed. Geometries were loaded to systemic pressure after accounting for pre-stress geometry. With user-defined fiber-embedded Ogden hyperplastic material model, finite element analyses were performed to obtain wall stress distributions. The 99th-percentile and mean longitudinal and circumferential wall stresses were determined. Statistical analyses were performed with R.
Results: The 99th-percentile longitudinal wall stresses on BAV-aTAA at systolic pressure were 372±128kPa vs 345±174kPa vs 220±50.2kPa in aortic sinuses, sinotubular junction (STJ), and ascending aorta, respectively, where stresses were significantly different between sinuses and ascending aorta (p<1e-5) and between STJ and ascending aorta (p<1e-4), but not between STJ and sinuses (p=0.60). The 99th-percentile circumferential wall stresses at systolic pressure were 477±107kPa vs 961±443kPa vs 419±83.2kPa for aortic sinuses, STJ, and ascending aorta, respectively, where stresses were significantly different between STJ and ascending aorta (p<1e- 13) and between STJ and sinuses (p<1e-12), but not between sinuses and ascending aorta (p=0.58). The 99th-percentile longitudinal wall stresses at systolic pressure were 209±41.3kPa vs 234±73.4kPa (p=0.065), while 99th-percentile circumferential wall stresses were 353±48.1kPa vs 542±186kPa (p<1e-6) on greater vs. lesser curvature, respectively.

Conclusions: Circumferential and longitudinal wall stresses were greater in the aortic root than the ascending aorta on BAV-aTAA patients. Longitudinal stresses were greatest at the aortic sinuses, while circumferential stresses were largest at the STJ. Depending on the respective wall strengths in these regions, these results suggest regions with greater tendency for initial intimal tears to occur in BAV-aTAA patients.

  1. Axel Gomez, BS, Zhongjie Wang, PhD, Yue Xuan, PhD, Andrew D. Wisneski, MD, Michael D. Hope, MD, Julius M. Guccione, PhD, Liang Ge, PhD, and Elaine E. Tseng, MD. Wall Stress Distribution in Bicuspid Aortic Valve Associated Ascending Thoracic Aortic Aneurysms. Presented at the Society of Thoracic Surgeons, 55th Annual Meeting, January 28, 2019, San Diego, CA.

 

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