P181. Investigating Stiffness and Primary Tear Hemodynamics in Acute Uncomplicated Type B Aortic Dissection Using 4D Flow Magnetic Resonance Imaging
Presented During: POD Abstracts (Available for viewing in the exhibit hall for the duration of the meeting)
Atlanta, GA
United States - Contact Me
Hannah Cebull is a postdoctoral fellow in the Department of Radiology & Imaging Sciences at Emory University working with Dr. Bradley Leshnower and Dr. Marina Piccinelli.
Thursday, April 25, 2024: 5:38 PM - 7:00 PM
Sheraton Times Square
Room: Central Park
Description
Objective: Currently, the 1st line therapy for acute uncomplicated type B aortic dissection (AUTBAD) is optimal medical therapy (OMT), providing excellent short-term results but a high rate of failure in the chronic phase. Thoracic endovascular aortic repair (TEVAR) is highly effective for remodeling the aorta in the acute phase, but less effective in the chronic phase. Ideally, patients with AUTBAD who fail OMT could be identified based upon data from non-invasive imaging modalities in the acute phase and undergo TEVAR. In this case study of a patient with an AUTBAD who failed OMT, we examine anatomic characteristics from the computed tomography angiogram (CTA) and hemodynamic metrics derived from 4D flow magnetic resonance imaging (MRI) before and after TEVAR.
Methods: The patient is a 48 year old male who presented with an AUTBAD and treated with OMT and discharged home. During his index hospitalization he underwent both CTA and 4D flow MRI exams. He returned for a surveillance visit at 3 months and a CTA demonstrated a rapid 1.6 cm growth of his descending thoracic aorta (DTA) to a size of 5.8 cm. He underwent TEVAR and had repeat CTA and 4D flow MRI scans 1 month post-TEVAR.
Maximum aortic diameters, primary tear area, and distance from the left subclavian artery (LSA) were measured from the CTAs. From the 4D flow MRI, we investigated primary tear and false lumen flow, wall shear stress, and pulse wave velocity (PWV) which is used as a stiffness index. After segmenting the true (TL) and false lumen (FL), a plane was placed perpendicular to the tear flow and in the FL to accurately measure peak velocity and assess FL flow (Materialise Mimics; Ansys EnSight). Wall shear stress (WSS) vectors were calculated using a previously developed method that multiplies blood viscosity, the rate of deformation tensor, and normal vector over the cardiac cycle. We estimated PWV by using a cross correlation method to measure lag time between flow waveforms at evenly spaced planes (4 mm) throughout the aorta compared to one reference plane at the aortic root.
Results: The index CTA maximum aortic diameter was 4.2 cm, with a primary intimal tear in Zone 3 (5.5 cm distal to LSA) measuring 22 mm in diameter and total area 380 mm2. The maximum FL diameter was 25 mm. At 3 months, there was proximal DTA growth (5.8 cm; Figure 1a). TEVAR resulted in complete FL thrombosis throughout the entire DTA.
The index 4D flow MRI revealed a peak velocity through the primary intimal tear of 180 cm/s, which is the highest recorded velocity in our 4D flow MRI database of AUTBAD (Figure 1b). There was substantial retrograde flow in the pre-tear region (net flow = -20.5 ml/cycle). The WSS opposite the tear in the FL was in the top 5% of estimated WSS (> 1 Pa) in the aorta (Figure 1c). PWV on the index 4D flow MRI was 3.6 m/s, and increased to 13.3 m/s following TEVAR, indicating a significant increase in aortic stiffness (Figure 1d).
Conclusions: This case study demonstrates the feasibility of collecting in vivo flow from AUTBAD patients using 4D flow MRI. This hemodynamic information may provide important prognostic data regarding patients at high risk for OMT failure. Furthermore, there is a significant increase in aortic stiffness following TEVAR, which may have significant implications on blood pressure and adverse cardiac remodeling. These adverse effects of thoracic aortic stents must be considered when deciding on optimal therapy for AUTBAD patients.
Authors
Hannah Cebull (1), Minliang Liu (2), Hai Dong (2), John Elefteriades (3), Rudolph Gleason (2), Marina Piccinelli (4), John Oshinski (5), Bradley Leshnower (6)
Institutions
(1) Emory University, United States, (2) Georgia Institute of Technology, Atlanta, GA, (3) Yale New Haven Hospital, New Haven, CT, (4) Emory University, Atlanta, GA, (5) Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, (6) Emory University Hospital, Atlanta, GA
Methods: The patient is a 48 year old male who presented with an AUTBAD and treated with OMT and discharged home. During his index hospitalization he underwent both CTA and 4D flow MRI exams. He returned for a surveillance visit at 3 months and a CTA demonstrated a rapid 1.6 cm growth of his descending thoracic aorta (DTA) to a size of 5.8 cm. He underwent TEVAR and had repeat CTA and 4D flow MRI scans 1 month post-TEVAR.
Maximum aortic diameters, primary tear area, and distance from the left subclavian artery (LSA) were measured from the CTAs. From the 4D flow MRI, we investigated primary tear and false lumen flow, wall shear stress, and pulse wave velocity (PWV) which is used as a stiffness index. After segmenting the true (TL) and false lumen (FL), a plane was placed perpendicular to the tear flow and in the FL to accurately measure peak velocity and assess FL flow (Materialise Mimics; Ansys EnSight). Wall shear stress (WSS) vectors were calculated using a previously developed method that multiplies blood viscosity, the rate of deformation tensor, and normal vector over the cardiac cycle. We estimated PWV by using a cross correlation method to measure lag time between flow waveforms at evenly spaced planes (4 mm) throughout the aorta compared to one reference plane at the aortic root.
Results: The index CTA maximum aortic diameter was 4.2 cm, with a primary intimal tear in Zone 3 (5.5 cm distal to LSA) measuring 22 mm in diameter and total area 380 mm2. The maximum FL diameter was 25 mm. At 3 months, there was proximal DTA growth (5.8 cm; Figure 1a). TEVAR resulted in complete FL thrombosis throughout the entire DTA.
The index 4D flow MRI revealed a peak velocity through the primary intimal tear of 180 cm/s, which is the highest recorded velocity in our 4D flow MRI database of AUTBAD (Figure 1b). There was substantial retrograde flow in the pre-tear region (net flow = -20.5 ml/cycle). The WSS opposite the tear in the FL was in the top 5% of estimated WSS (> 1 Pa) in the aorta (Figure 1c). PWV on the index 4D flow MRI was 3.6 m/s, and increased to 13.3 m/s following TEVAR, indicating a significant increase in aortic stiffness (Figure 1d).
Conclusions: This case study demonstrates the feasibility of collecting in vivo flow from AUTBAD patients using 4D flow MRI. This hemodynamic information may provide important prognostic data regarding patients at high risk for OMT failure. Furthermore, there is a significant increase in aortic stiffness following TEVAR, which may have significant implications on blood pressure and adverse cardiac remodeling. These adverse effects of thoracic aortic stents must be considered when deciding on optimal therapy for AUTBAD patients.
Authors
Hannah Cebull (1), Minliang Liu (2), Hai Dong (2), John Elefteriades (3), Rudolph Gleason (2), Marina Piccinelli (4), John Oshinski (5), Bradley Leshnower (6)
Institutions
(1) Emory University, United States, (2) Georgia Institute of Technology, Atlanta, GA, (3) Yale New Haven Hospital, New Haven, CT, (4) Emory University, Atlanta, GA, (5) Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, (6) Emory University Hospital, Atlanta, GA
Presentation Duration
PODS will be on display in the exhibit hall for the duration of the meeting during exhibit hall hours. PODS will also be available for viewing on the meeting website. There is no formal presentation associated with your POD, but we encourage you to visit the PODS area during breaks to connect with those viewing.