Hemodynamics in aortic dissections: A fluid-solid interaction study in an idealized dissection model with a false lumen side branch.

Side-branches (SBs) emanating from the false lumen (FL) in Type-B aortic dissection (TBAD) has been shown to influence patency and FL growth, making FL hemodynamics crucial to understand. This study employs a strongly coupled Fluid-Solid interaction simulation to compare FL hemodynamics in four scenarios: (1) without SB (NSB), (2) single SB in FL (SB_FL), (3) single SB in FL with no re-entry tear (SB_FL_1T), and (4) single SB in true lumen (SB_TL). A pulsatile mass flow is imposed at the inlet, while 3-element windkessel models are applied at the outlets, ensuring equal total vascular resistance for all scenarios. While idealized in terms of geometry, the model incorporates residually stressed, externally supported and anisotropic tissue. Results demonstrate that SB presence leads to higher pressures in both TL and FL during systole, with the highest increase in systolic pressure when the SB emanates from the FL (∼6 mmHg vs ∼3 mmHg for SB_TL). A side branch in the FL reduces FL ejection fraction (FLEF) and leads to higher cycle-averaged transmembrane pressure (TMP¯), which however remains below 1 mmHg for all scenarios. NSB exhibits the highest dissected membrane displacement (∼8 mm), while SB_FL shows the lowest displacement across all planes (∼5.5 mm). These findings suggest that SBs in TBAD affect hemodynamics beyond an altered flow velocity field within the false lumen and, in a setting with maintained mass flow and total vascular resistance, leads to increased TL and FL pressures. The idealized nature of the geometry, however, is to be kept in mind when interpreting our data and extrapolating towards clinical reality.