What is the most common cause of a dissecting aneurysm?

The most common cause of a dissecting aneurysm is hypertension. Dissecting aneurysms occur when there is a tear in the intimal layer of an artery, allowing blood to flow between the layers of the arterial wall. This condition is often associated with underlying hypertension because the increased blood pressure can cause stress on the vessel walls, leading to damage and subsequent dissection.

Chronic hypertension is particularly damaging as it can lead to changes in the structure of the arterial wall, including cystic medial degeneration and weakening of the layers, which facilitate the development of a dissection. In untreated or poorly controlled hypertension, these changes can occur more rapidly, increasing the risk of a dissecting aneurysm.

While genetic disorders, atherosclerosis, and infections can contribute to vascular diseases, they are not the most common causes of dissecting aneurysms. Specifically, atherosclerosis primarily affects the larger arteries and is more associated with true aneurysms rather than dissections. Infections are rare causes of arterial dissection and do not have a significant role in the vast majority of cases. Thus, hypertension remains the predominant risk factor and cause for this life-threatening condition.