The Role of Branch Vessels in Aortic Type B Dissection: An in vitro Study

Abstract

In acute type B aortic dissection (ABAD) a patent false lumen portends a poor outcome. Patent branch vessels originating from the false lumen in a type B aortic dissection are assumed to contribute to persistent blood flow and patent false lumen. Therefore, the morphologic changes of the false lumen generated by different outflow rates in an in vitro model were investigated. An artificial dissection was created in two ex vivo porcine aortas. A thin cannula was placed in the false lumen, simulating a branch vessel originating from it. The aorta was positioned in a validated in vitro circulatory system with physiological pulsatile flow (1,500-2,700 mL/minute) and pressure characteristics (130/70 mm Hg). The cannula was attached to a small silicone tube with an adjustable valve mechanism. Three different valve settings were used for creating outflow from the false lumen (fully closed, opened at 50%, and fully opened at 100%). Measurements of lumen areas and flow rates were assessed with time-resolved magnetic resonance imaging. In order to study reproducibility, the experiment was performed twice in two different porcine aortas with a similar morphology. Increasing antegrade outflow through the branch vessel of the false lumen resulted in a significant (p < .01) increase of the mean false lumen area at the proximal and distal location in both models. The distal false lumen expanded up to 107% in the case of high outflow via the false lumen through the branch vessel. Increasing antegrade outflow through a branch vessel originating from the false lumen when no distal re-entry tear is present results in an expansion of the cross sectional false lumen area.