Geometric and flow features of type B aortic dissection: initial findings and comparison of medically treated and stented cases.

Uncomplicated acute type B aortic dissections are usually treated medically, but they can become acutely complicated by rapid expansion, rupture and malperfusion syndromes and in the longer term by chronic dilatation and aortic aneurysm formation. The objective of this study is to use computational fluid dynamics reconstructions of type B aortic dissections to compare geometric and haemodynamic factors between the cases selected for medical treatment and the cases selected for thoracic endovascular aortic repair (TEVAR), and to examine whether any of these factors are associated with the outcome of the medically treated group. This study includes eight type B dissection cases, with four in each group. Aortic flow analyses were carried out based on patient-specific anatomy at initial presentation before treatment. Comparisons between the two groups show that the false lumen to true lumen volume ratio is considerably higher in patients selected for TEVAR. Results from the four medically treated cases indicate that the size of the primary entry tear is the key determinant of the false lumen flow rate, which may influence the long-term outcome of medically treated patients. Potential relations between flow related parameters based on initial anatomy and subsequent anatomical changes in the medically treatment group were examined. Our initial findings based on the limited cases are that high relative residence time is a strong predictor of subsequent false lumen thrombosis, whereas pressure difference between the true and false lumen as well as the location of the largest pressure difference may be associated with the likelihood of subsequent aortic expansion.