A tear in the aorta, the heart condition that killed actor John Ritter, is a rare medical disaster that can strike without warning.
The condition, called an aortic dissection, is a break in the main artery that carries blood from the heart. The lining of the aorta tears, separating - or dissecting - the middle layer of the vessel wall from the still intact outer layer.
About three-quarters of these occur in people age 40 to 70, and the peak years are 50 to 65. Ritter was 54.
About one-third of patients die within the first 24 hours, and half die within two days.
Typically doctors treat patients in intensive care with drugs to reduce heartbeat and blood pressure. Surgery can sometimes repair the tear, although the risk is substantial.
A variety of medical conditions can cause the artery wall to deteriorate, leading to the tear. The most common is high blood pressure. Others include inherited connective tissue disorders and birth defects.
Symptoms usually begin with sudden severe chest pain. As the tear progresses, it can block off the points at which other arteries branch away from the aorta, stopping blood flow. This can trigger a stroke or heart attack, among other things, depending on which arteries are affected.
Evidence of aortic dissection is found in between 1 percent and 3 percent of all autopsies.