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How can atherosclerosis cause an aneurysm in the aorta or iliac arteries?

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The role of coronary artery disease in heart attack — cardiovascular disease This micrograph shows a cross section of a coronary artery narrowed by an atherosclerotic plaque (purplish matter inside the artery). Most heart attacks are caused by the rupture of an atherosclerotic plaque, which triggers the formation of a clot that abruptly blocks blood flow to part of the heart muscle.

Atherosclerosis contributes to the formation of an aneurysm in the aorta or iliac arteries primarily by compromising the structural integrity of the vessel wall.1

An aneurysm is defined as the widening of an artery resulting from the weakness or destruction of the medial layer (the muscular middle layer) of the blood vessel. In the context of atherosclerosis, the disease process involves the accumulation of fatty plaques that can lead to mechanical instability of the arterial wall. As these changes occur, the artery loses its elasticity and structural strength.231

Under the constant pressure of circulating blood, this weakened arterial wall becomes unable to maintain its normal shape and begins to enlarge or dilate. If left untreated, these aneurysms can lead to severe complications, including the formation of blood clots that may occlude downstream vessels, or a potentially fatal rupture and hemorrhage.21