Volumetric analysis of the initial index computed tomography scan can predict the natural history of acute uncomplicated type B dissections

Abstract

Objective: Our objective was to characterize the predictive impact of computed tomography (CT) scan volumetric analysis on the natural history of acute uncomplicated type B aortic dissections (ADs).

Methods: We conducted a retrospective review of patients with acute type B ADs from 2009 to 2014. On an iNtuition workstation (TeraRecon, Foster City, Calif), volume measurements were obtained using the true lumen volume (TLV), false lumen volume (FLV), and total aortic volume from the left subclavian artery to the celiac artery. Growth rate was calculated as the change in maximal diameter between first and last available CT scans during the time interval. The primary outcome of the study was delayed aortic intervention. P < .05 was considered statistically significant.

Results: During a 5-year period, 164 patients had CT scan evidence of acute type B ADs; 11 patients were excluded for lack of subsequent follow-up imaging; 36 patients who underwent urgent repair (<14 days from presentation) were also excluded. We evaluated a total of 117 patients: 85 patients who did not require intervention and 32 who underwent delayed (>14 days) thoracic endovascular aneurysm repair (29) or open repair (3). Mean age was 66 ± 12 years. Mean TLV/FLV ratio on initial CT scan was significantly higher in patients who did not eventually require an operation (1.55 vs 0.82; P = .02). The mean growth rate was higher in those eventually requiring operation (2.47 vs 0.42 mm/mo; P = .003). Patients were divided into three subgroups on the basis of their initial imaging TLV/FLV ratios (<0.8, 0.8-1.6, and >1.6). There was a significant difference in the growth rates between these three groups (4.6 vs 2.4 vs 0.8 mm/mo; P < .025). Area under the receiver operating characteristic curve analysis revealed that a TLV/FLV ratio <0.8 was highly predictive for requiring an intervention (area = 0.8; sensitivity, 69%; specificity, 84%: positive predictive value, 71%; negative predictive value, 81%), with an odds ratio of 12.2 (confidence interval, 5-26; P < .001). Conversely, a TLV/FLV ratio of >1.6 was highly predictive for freedom from delayed operation (sensitivity, 91%; specificity, 42%; positive predictive value, 61%; negative predictive value, 86%). After Kaplan-Meier analysis, 1-year and 2-year survival free of aortic interventions was 60% and 42% with a TLV/FLV ratio <0.8 and 92% and 82% with a ratio >1.6 (P = .001).

Conclusions: Initial CT scan volumetric analysis in patients presenting with uncomplicated acute type B ADs is a useful tool to predict growth and need for future intervention.