Importance of false lumen thrombosis in type B aortic dissection

Background: Partial thrombosis of the false lumen has been reported as a significant predictor of mortality during follow-up in patients with acute type B aortic dissection. The purpose of this study was to investigate the correlation of false lumen thrombosis and aortic expansion during follow-up in patients with acute type B aortic dissection. Methods: All medically treated patients with acute type B aortic dissection observed in 4 cardiovascular referral centers between 1998 and 2011, with admission and follow-up computed tomography or magnetic resonance imaging scans, were included. Aortic diameters of the dissected aortas were measured at 4 levels on the baseline and follow-up scans, and annual growth rates were calculated. Univariate and multivariate regression analyses were used to investigate the effect of false lumen thrombosis on aortic growth rate. Results: A total of 84 patients were included, of whom 40 (47.6%) had a partially thrombosed false lumen, 7 (8.3%) had a completely thrombosed false lumen, and 37 (44.0%) had a patent false lumen. A total of 273 of the 336 (81.3%) evaluated aortic levels were dissected segments. Overall, the mean aortic diameter increased significantly at all evaluated levels (P < .001). Univariate analysis showed that annual aortic growth rates were significantly higher in those segments having a false lumen with partial thrombosis (mean, 4.25 \ub1 10.2) when compared with the patent group (mean, 2.10 \ub1 5.56; P = .035). In multivariate analysis, partial lumen thrombosis was an independent predictor of higher aortic growth (adjusted mean difference, 2.05 mm/year; 95% confidence interval, 0.10-4.01; P = .040). Conclusions: In patients with acute type B aortic dissection, aortic segments with a partially thrombosed false lumen have a significantly higher annual aortic growth rate when compared with those presenting with patent or complete thrombosis of the false lumen. Therefore, patients with partial thrombosis require more intensive follow-up and may benefit from prophylactic intervention