Ascending Aortic Aneurysm Is an Inherited Disease: A Contemporary Literature Review Based on Hill's Criteria of Specificity, Strength of Association, and Biological Coherence.

There is growing evidence of a differential etiological basis for thoracic aortic aneurysms (TAA), with ascending (As) TAAs being genetically mediated and descending (Des) TAAs more strongly related to acquired pathologies. A comprehensive literature review of this hypothesis has not been carried out. We carried out a systematic literature review based on the latest guidelines on TAA endorsed by the American Heart Association. The etiologies were classified as genetic and inherited, the studies were tabulated accordingly, and Hill's epidemiological criteria of causality were applied. We found 38 studies addressing the etiology of TAAs. Out of these, 17 were about genetic causes, 9 about acquired causes, and 4 had information regarding both etiologies. Multiple genetic studies showed a strong association of As TAA with different genetic mutations. Contrary to commonly held beliefs, acquired causes, that is, dyslipidemia, diabetes, and atherosclerosis, were negatively associated with As TAA and positively associated with Des TAA. Hypertension was only associated with Des TAA and dissections (TAAD), not with As TAA. Multiple studies fulfilled the criteria of strength of association (n = 4), consistency (n = 9), specificity (n = 5), temporality (24), biological gradient (n = 3), plausibility (n = 38), biological coherence (n = 25), experiment (n = 4), and analogy (n = 6). Our literature review supports the hypothesis that As TAA is genetically mediated and Des TAA is predominantly an acquired pathology, and supports the argument for genetic testing in all cases of As TAA.

Influence of Differential Calcification in the Descending Thoracic Aorta on Aortic Pulse Pressure.

PURPOSE: Multiple studies have shown pulse pressure (PP) to be a strong predictor of aortic calcification. However, no studies are available that correlate PP with aortic calcification at the segmental level. METHODS: We identified 37 patients with aortic PP measured during cardiac catheterization. Their noncontrast chest computed tomography scans were evaluated for the presence of calcium in different segments (ascending aorta, arch of aorta [arch], descending aorta) and quantified. Patients with calcification (Calcified Group A) were compared against patients without calcification (Noncalcified Group B) in terms of PP, calcification and compliance. RESULTS: The mean of the total calcium score was higher in the descending aorta than the arch or ascending aorta (691 vs 571 vs 131, respectively, P<0.0001). PP had the strongest correlation with calcification in the descending aorta (r=0.47, P=0.004). Calcified Group A had a much higher PP than Noncalcified Group B, with the greatest difference in the descending aorta (20 mmHg, P<0.0001), lesser in the ascending aorta (10 mmHg, P=0.12) and the least in the arch (5 mmHg, P=0.38). Calcified Group A patients also had much lower compliance than Noncalcified Group B patients, with the greatest difference among groups seen in the descending aorta (0.7 mL/mmHg, P=0.002), followed by the ascending aorta, then arch. CONCLUSIONS: These are the first data to evaluate the relative impact of aortic segments in PP. Finding the greatest amount of calcification along with greatest change in PP and compliance in the descending aorta makes a case that the descending aorta plays a major role in PP as compared to other segments of the thoracic aorta.