Baseline 4D Flow-Derived in vivo Hemodynamic Parameters Stratify Descending Aortic Dissection Patients With Enlarging Aortas

Abstract

PurposeThe purpose of our study was to assess the value of true lumen and false lumen hemodynamics compared to aortic morphological measurements for predicting adverse-aorta related outcomes (AARO) and aortic growth in patients with type B aortic dissection (TBAD).Materials and MethodsUsing an IRB approved protocol, we retrospectively identified patients with descending aorta (DAo) dissection at a large tertiary center. Inclusion criteria includes known TBAD with ≥ 6 months of clinical follow-up after initial presentation for TBAD or after ascending aorta intervention for patients with repaired type A dissection with residual type B aortic dissection (rTAAD). Patients with prior descending aorta intervention were excluded. The FL and TL of each patient were manually segmented from 4D flow MRI data, and 3D parametric maps of aortic hemodynamics were generated. Groups were divided based on (1) presence vs. absence of AARO and (2) growth rate ≥ vs. < 3 mm/year. True and false lumen kinetic energy (KE), stasis, peak velocity (PV), reverse/forward flow (RF/FF), FL to TL KE ratio, as well as index aortic diameter were compared between groups using the Mann–Whitney U or independent t-test.ResultsA total of n = 51 patients (age: 58.4 ± 15.0 years, M/F: 31/20) were included for analysis of AARO. This group contained n = 26 patients with TBAD and n = 25 patients with rTAAD. In the overall cohort, AARO patients had larger baseline diameters, lower FL-RF, FL stasis, TL-KE, TL-FF and TL-PV. Among patients with de novo TBAD, those with AAROs had larger baseline diameter, lower FL stasis and TL-PV. In both the overall cohort and in the subgroup of de novo TBAD, subjects with aortic growth ≥ 3mm/year, patients had a higher KE ratio.ConclusionOur study suggests that 4D flow MRI is a promising tool for TBAD evaluation that can provide information beyond traditional MRA or CTA. 4D flow has the potential to become an integral aspect of TBAD work-up, as hemodynamic assessment may allow earlier identification of at-risk patients who could benefit from earlier intervention.

Entry tear hemodynamics using 4D flow MRI in a patient with acute type B aortic dissection

“…4D flow MRI acquired concurrently exhibited high velocity flow through the proximal entry tear into the FL. The entry tear flow and velocity in this patient were the highest values we have seen so far in our institutional TBAD cohort [4] . We hypothesize that this high velocity, high volume flow ultimately led to increased pressurization in the FL and eventual rupture, as has been suggested in other studies [7] .…”

“…MRA requires longer scan times than CTA, which can be prohibitive in the acute setting due to the often unstable clinical condition of TBAD patients. However, neither of these methods provides hemodynamic profiles of flow alterations in the FL in TBAD, which can be associated with adverse outcomes [4] . Prior to this patient's rapid decompensation, his vitals and physical exam were stable for 24 hours, suggesting the patient could be managed with anti-impulse therapy alone without any surgical intervention.…”

“…4-dimensional (4D) flow magnetic resonance imaging (MRI) is a useful diagnostic tool to characterize the complex hemodynamics and flow patterns seen in TBAD patients [ 2 , 3 ]. Recent studies have shown that larger maximum aortic diameter, higher FL forward flow, and greater FL peak velocity are associated with adverse outcomes in TBAD [4] , [5] , [6] . Here, we present 4D flow MRI of a patient acutely presenting with TBAD and a large primary entry tear.…”

Hemodynamic Evaluation of Type B Aortic Dissection Using Compressed Sensing Accelerated 4D Flow MRI

“…3D parametric maps of aortic hemodynamics were derived using in‐house analysis tools (MATLAB; The MathWorks, Natick, MA) similar to a recently reported workflow 6,24 . The 4D flow velocity data were interpolated to 1 mm 3 voxels using spline interpolation.…”

The Influence of Minor Aortic Branches in Patient-Specific Flow Simulations of Type-B Aortic Dissection

“…Next, Q was decomposed into forward and reverse flow rates to assess the degree of retrograde flow in the FL, which may be linked with TBAD progression. 14 At any given timestep, forward and reverse flow regions P F and P R were defined on a given FL plane, P, as follows:…”