"Atherosclerotic plaques and the risk factors that cause them, including hypertension, classically have been considered important potential causes of the expansion of the aorta," says Bijoy Khandheria, M.D., a Mayo Clinic cardiologist and study author. "Intuitively, it makes sense that high blood pressure would stretch the vessel walls and make them more likely to become enlarged. This study shows that while these risk factors are highly important in a host of diseases and conditions, they are bit players when it comes to causing the dilatation of the aorta that can lead to aneurysm."
The researchers studied the expansion of the aorta in a sample of 581 Olmsted County, Minn., residents using transesophageal echocardiography (TEE). TEE is similar to fetal ultrasounds used during pregnancy and conventional echocardiographic heart imaging. Instead of coming from outside of the body, however, the ultrasound waves in TEE are emitted from a probe that is inserted down the throat. This eliminates the interference of the breastbone, and makes it possible to obtain much clearer images of the great blood vessels surrounding the heart.
The study found that age, gender and body size together account for one-third or more of the cases of aortic dilatation, while atherosclerosis and related risk factors only explained 3 percent.
"There has been a tendency recently to refer to aneurysms as 'athersclerotic aneurysms,'" explains Dr. Khandheria. "But the fact that plaques -- even complex or severe ones -- are very common, while aneurysms are rare, supports the conclusion that atherosclerosis and its risk factors are not likely to blame for aneurysms in the major blood vessels of the chest. Other factors and processes, including genetic diseases similar to Marfan syndrome, seem to be more important. In addition to providing reference values to physicians on the normal range of aorta measurements in a community, this study should spur further investigation into those other causes."