The great circulatory paradox.

A review of the relationship between infarction and arterial obstruction in four major vascular territories--brain, gut, leg, and heart--shows that infarction without demonstrable arterial stenosis is common in the brain and gut though rare in the heart and leg. The converse--arterial occlusion without infarction--is common in all four territories. Three factors are recognised as important causes of infarction without demonstrable arterial stenosis--embolism (with rapid disintegration of the clot), spasm, and acute circulatory failure. The importance of cerebral embolism and coronary spasm has only recently been established. An appreciation of the role of factors other than atheroma in the aetiology of infarction is essential for rational prevention and treatment.