False Lumen Flow Patterns and their Relation with Morphological and Biomechanical Characteristics of Chronic Aortic Dissections. Computational Model Compared with Magnetic Resonance Imaging Measurements

Abstract

Aortic wall stiffness, tear size and location and the presence of abdominal side branches arising from the false lumen (FL) are key properties potentially involved in FL enlargement in chronic aortic dissections (ADs). We hypothesize that temporal variations on FL flow patterns, as measured in a cross-section by phase-contrast magnetic resonance imaging (PC-MRI), could be used to infer integrated information on these features. In 33 patients with chronic descending AD, instantaneous flow profiles were quantified in the FL at diaphragm level by PC-MRI. We used a lumped-parameter model to assess the changes in flow profiles induced by wall stiffness, tear size/location, and the presence of abdominal side branches arising from the FL. Four characteristic FL flow patterns were identified in 31/33 patients (94%) based on the direction of flow in systole and diastole: BA = systolic biphasic flow and primarily diastolic antegrade flow (n = 6); BR = systolic biphasic flow and primarily diastolic retrograde flow (n = 14); MA = systolic monophasic flow and primarily diastolic antegrade flow (n = 9); MR = systolic monophasic flow and primarily diastolic retrograde flow (n = 2). In the computational model, the temporal variation of flow directions within the FL was highly dependent on the position of assessment along the aorta. FL flow patterns (especially at the level of the diaphragm) showed their characteristic patterns due to variations in the cumulative size and the spatial distribution of the communicating tears, and the incidence of visceral side branches originating from the FL. Changes in wall stiffness did not change the temporal variation of the flows whereas it importantly determined intraluminal pressures. FL flow patterns implicitly codify morphological information on key determinants of aortic expansion in ADs. This data might be taken into consideration in the imaging protocol to define the predictive value of FL flows.

Proposed classification of endoleaks after endovascular treatment of Stanford type-B aortic dissections

“…60 Endoleak following prior treatment of acute/subacute TBAD versus chronic TBAD. Direction of flow into FL: Dynamic MRI or CTA, and contrast enhanced duplex sonography may enable accurate description of flow direction and patterns in a manner that may have important clinical relevance on the decision to treat and type of treatment modality. 61–63 Low flow versus high flow endoleak: Whereas high resistance/low flow endoleak has a high chance of spontaneous regression, low-resistance/high-flow or a high resistance poor outflow “to-fro” flow endoleak patterns are associated with high rates of sac enlargement, rupture, and reintervention. 46,47,64–66 Recent advances in phase-contrast 4D-MRI can enable accurate visualization and quantification of flow characteristics in patients with aortic dissection.…”

“…Direction of flow into FL: Dynamic MRI or CTA, and contrast enhanced duplex sonography may enable accurate description of flow direction and patterns in a manner that may have important clinical relevance on the decision to treat and type of treatment modality. 61–63…”

Hematoma intramural e úlcera penetrante da aorta: incertezas e controvérsias

“…It is clear that other factors, such as the size of the intimal tear and presence or absence of large reentry orifices with considerable retrograde flow, play important roles in compression of the true lumen. [24][25][26] In the specific case of IMH, it has been demonstrated experimentally that peak stress on the tunica media (peak wall stress) is much greater than is observed in an artery without hematoma, which might explain progression to rupture in the direction of the lumen or frank dissection. 27…”

The Influence of Aortic Wall Elasticity on the False Lumen in Aortic Dissection: An In Vitro Study

“…5 Hemodynamics, dissection morphology, and aortic wall elasticity have a major influence on the pressure in the false lumen. 6 In contrast to the aortic wall elasticity, the influence of hemodynamics and dissection morphology have been investigated often in multiple in vitro and ex vivo studies. 7,8 Aortic wall elasticity is variable and often altered in aortic dissections.…”