Analysis of Aortic Growth Rates in Uncomplicated Type B Dissection

Uncomplicated type B dissections have historically been treated medically with hemodynamic control. Early progression of the disease and late aneurysmal dilation have been considered as indications for intervention. The aim of this study is to analyze growth rate patterns of type B dissections based on computed tomography (CT) measurements over time.

We conducted a retrospective review of patients with acute type B dissection from 2008 to 2014 who had at least 2 follow-up CT scans. Patients with rapid progression requiring interventions were also included. Using M2S software (M2S, Lebanon, NH), we calculated the mean centerline diameter of the true and false lumens at 3 different sites of the descending aorta. Growth rate was calculated as the change in maximal diameter between the first interval and last available CT scans. Primary outcome was to compare the growth rate pattern between the 2 time intervals. Secondary outcomes included early and delayed aortic intervention and overall mortality (OM).

A total of 108 patients were included. Average age of patients was 58.7 years. Median follow-up time was 3 months for the first CT and 32 months for the second. OM was 27.8% (n = 30), whereas the disease-specific mortality was 11.1% (n = 12). Thirty-seven percent (n = 40) required operative intervention (18 open and 22 endovascular repair): 20 at 30 days, 12 at 12 months, and 8 patients at >1 year. Mean aortic growth rate was higher in the first time interval compared with the second: 0.89 vs. 0.19 mm/month (P < 0.05) at the proximal descending aorta, 1.01 vs. 0.18 mm/month (P < 0.05) at the mid-descending aorta, and 0.65 vs. 0.28 mm/month; (P < 0.05) at the distal descending aorta. Those who underwent intervention had a higher aortic growth rate at early and late interval (P < 0.05). Age and number of comorbidities were associated with OM. Thrombosis of the false lumen did not affect the mortality and intervention rate.

Type B dissection is associated with aortic growth over time. The overall growth rate was not linear with a more prominent initial phase. Faster aortic growth rate is associated with an increased intervention rate, whereas advanced age and number of comorbidities are associated with increased mortality. Prospectively designed studies are needed to identify the subgroup of patients who may benefit from early intervention based on growth rate measurements.