Complicated and Uncomplicated Isolated Abdominal Aortic Dissections Demonstrate Different Patient Characteristics and Outcomes.

Background: Isolated abdominal aortic dissection (IAAD) is a rare entity with poorly defined risk factors and wide variation in management. We set forth to compare patient characteristics, management, and outcomes of uncomplicated isolated abdominal aortic dissection (uIAAD) versus high risk and complicated isolated abdominal aortic dissection (hrcIAAD) to investigate whether these categories can be utilized to guide IAAD management and provide risk stratification for intervention.

Methods: Retrospective chart review was performed to identify all patients with spontaneous IAAD at a tertiary health care system between 1996 and 2022. Demographics, comorbidities, factors relating to initial presentation including imaging findings, and dissection outcomes including long-term all-cause mortality and aortic-related mortality from time of dissection to final available record were abstracted. IAAD demonstrating rupture or malperfusion were designated as complicated, those with aortic diameter greater than 4 cm on presentation or refractory pain were designated as high risk, and the remainder was designated as uIAAD. All variables were compared between hrcIAAD and uIAAD using Fisher's exact test, unpaired t-test, and Mann-Whitney U-test as appropriate.

Results: Over the study period, 74 patients presented with spontaneous IAAD (mean age 60 ± 16 years, 61% male) with postdissection follow-up records to an average of 6.8 ± 5.8 years. Of these, 76% presented with uIAAD versus 24% with hrcIAAD. hrcIAAD was diagnosed at a significantly younger age on average than uIAAD (52 ± 14 vs. 62 ± 16 years, P = 0.02), was less likely to present with concomitant hyperlipidemia (0% vs. 41%, P < 0.01), coronary artery disease (6% vs. 47%, P < 0.01), and prior smoking history (39% vs. 72%). hrcIAAD was more likely to present in patients with a genetic aortopathy (27% vs. 7%, P = 0.03). Hypertension was not significantly different between groups. Patients with hrcIAAD were significantly more likely to present with extension into iliac arteries compared to uIAAD (61% vs. 18%, P < 0.01). A much higher proportion of hrcIAAD required hospitalization compared to uIAAD (83% vs. 30%, P < 0.01) and operative intervention (67% vs. 7%, P < 0.01). While there was no significant difference in all-cause mortality between groups, there was a significant difference between aortic-related mortality which only occurred in those with hrcIAAD (28% vs. 0%, P < 0.01).

Conclusions: Comparison of long-term outcomes suggests that hrcIAAD is associated with increased hospitalization and need for operative intervention compared to uIAAD. Significant differences in atherosclerotic risk factors and proportions of connective tissue disease history between patients who present with hrcIAAD and uIAAD suggest that differences in underlying etiology are largely responsible for whether IAAD progresses towards rupture or has a more benign course and should be considered in risk stratification to guide more specific and targeted management of IAAD.