Cause-Specific Mortality of Type B Aortic Dissection and Assessment of Competing Risks of Mortality

Objective: The aim of the study was to determine cause-specific mortality in TBAD and to evaluate the clinical characteristics associated with aorta-related and non aorta-related mortality.
Methods: Clinical and administrative records were reviewed for patients with acute TBAD between 1995 and 2017. Demographics, comorbidities, presentation, and initial imaging findings were abstracted. Cause of death was ascertained through a multimodality approach using electronic health records, obituaries, social media, Social Security Death Index, and state mortality records. Causes of death were classified as aorta related, nonaorta related, or unknown. A Fine-Gray multivariate competing risk regression model for sub distribution hazard ratio was employed to analyze the association of clinical characteristics with aorta-related and non aorta-related mortality.

Results: A total of 275 individuals met inclusion criteria (61.1 6 13.7 years, 70.9% male, 68% white). Mean survival after discharge was 6.3 6 4.7 years. Completeness of follow-up Clark C index was 0.87. All-cause mortality was 50.2% (n . 138; mean age, 70.1 6 14.6 years) including an in-hospital mortality of 8.4%. Cause-specific mortality was aorta related, non aorta related, and unknown in 51%, 43%, and 6%, respectively. Compared with patients with non aorta-related mortality, patients with aorta-related mortality were younger at acute TBAD (69.5 6 11.2 years vs 61.6 6 15.5 years; P .001), underwent more descending thoracic aortic repairs (19.4% vs 45.8%; P . .002), and had a shorter survival duration(5.7 6 3.9 vs 3.4 6 4.5 years; P . .002). There was clear variation in cause of death by each decade of life, with higher aorta related mortality among those younger than 50 years and older than 70 years and a stepwise increase in non aorta related mortality with each increasing decade (P < .001). All-cause mortality at 1 year, 3 years, and 10 years was 15%, 24%, and 57%, respectively. After accounting for competing risks, the cumulative incidence of aorta-related mortality at
1 year, 3 years, and 10 years was 8.9%, 16.5%, and 27.2%, respectively, and that of non aorta-related mortality was 2.7%, 7.2%,and 29%, respectively. A maximum descending thoracic aortic diameter >4 cm was associated with an increase in hazard of aorta-related mortality by 84% (sub distribution hazard ratio, 1.84; 95% confidence interval, 1.03-3.28) on multivariate competing risk regression analysis.

Conclusions: TBAD is associated with high 10-year mortality. Those at risk for aorta-related mortality have a clinical phenotype different from that of individuals at risk for non aorta-related mortality. This information is important for building risk prediction models that account for competing mortality risks and to direct optimal and individualized surgical and medical management of TBAD.