Introduction

Localized dilation of an artery secondary to loss of smooth muscle and elastic tissue in the media.

In the elderly, aneurysms are most likely to occur at branching points (eg, the terminal aorta) or at areas of stress (eg, the popliteal artery) and are almost always of atherosclerotic origin. Systemic hypertension is a major risk factor. When a local dilation develops, blood flow velocity decreases, leading to increased pressure against the arterial wall. The increased pressure results in more dilation and release of elastases in the vessel wall, perpetuating a vicious circle that often terminates in rupture of the artery. Saccular aneurysms are more likely to rupture than fusiform aneurysms because the total wall pressure is applied to a smaller area. Clinical findings and prognosis vary with the aneurysm's location and size.