Which of the following statements about thoracic aortic aneurysm (TAA) is least accurate?

Thoracic aortic aneurysms (TAAs) can often be a complex condition, influenced by a variety of risk factors. The statement indicating that most TAAs are not degenerative is least accurate because the majority of TAAs have a degenerative etiology. Factors such as atherosclerosis, hypertension, and genetic disorders (like Marfan syndrome) contribute to the weakening and dilation of the aortic wall, leading to aneurysm formation. These degenerative processes are common and indicate that most TAAs arise from a degenerative background rather than being congenital or traumatic.

In contrast, the other statements accurately reflect the understanding of TAAs. The incidence rates given in the first statement are consistent with epidemiological data. The third statement about open repair is also supported by clinical studies, indicating that this surgical intervention can carry significant risks regarding mortality and morbidity. Finally, the fourth statement is substantiated by research showing that a substantial proportion of TAAs, specifically around 30% to 40%, indeed involve the descending thoracic aorta. These details reinforce the complexities and clinical implications surrounding thoracic aortic aneurysms.