What is Aortic Disease?

Excerpt from "Thoracic Aortic Aneurysms and Aortic Dissections"

Dianna M Milewicz, MD, PhD
Division of Medical Genetics
Department of Internal Medicine
University of Texas Medical School at Houston

and 

Van Tran-Fadulu, MS, CGC
Division of Medical Genetics
Department of Internal Medicine
University of Texas Medical School at Houston

Overview

Cardiovascular manifestations of familial thoracic aortic aneurysms and aortic dissections (TAAD) include: (1) dilatation of the aorta at the level of either the ascending aorta or the sinuses of Valsalva; and (2) aneurysms and dissections of the thoracic aorta involving either the ascending or descending aorta. Cardiovascular manifestations are usually the only findings. Affected individuals typically have progressive enlargement of the ascending aorta leading to either aortic dissection involving the ascending aorta (type A dissection) or consequent tear or rupture. The onset and rate of progression of aortic dilatation is highly variable.

Diagnosis/testing

TAAD is diagnosed based on the presence of dilatation and/or dissection of the thoracic aorta, absence of Marfan syndrome and other connective tissue abnormalities, and presence of a positive family history.

The primary manifestations of familial TAAD are either (1) dilatation of the ascending aorta at the level of the ascending aorta or at the level of the sinuses of Valsalva or (2) dissection of the ascending aorta or (3) both. Affected individuals typically have progressive enlargement of the ascending aorta leading to either an aortic dissection involving the ascending aorta (type A dissection) or rupture.

An aortic dissection is a tear in the inner layer (intimal layer) of the aortic wall that allows blood to enter and separate the inner and outer layers of the vessel in the media. This produces a false lumen or double-barreled aorta, which can reduce blood flow to the major arteries arising from the aorta. Dissections can weaken the outer wall, resulting in rupture or formation of an aneurysm. Dissections can occur with or without previous aortic aneurysm formation, but in the majority of individuals with familial TAAD, enlargement of the aorta typically precedes dissection [Milewicz et al 1998]. As an aneurysm enlarges, the aortic annulus can become stretched, leading to secondary aortic regurgitation.

Clinical features of aortic aneurysms and dissections are similar in males and females. The primary symptom of an aortic dissection is severe pain usually in the chest (front, back, or both), but occasionally in the abdomen when the tear involves the abdominal aorta. Dissections can also cause other signs and symptoms including pallor, pulselessness, paresthesiae, and paralysis.

The onset and rate of progression of aortic dilatation is highly variable even within families. The variable expression of the disorder means that one individual in the family may present with an aneurysm at a young age, whereas another individual may present at an elderly age. The mean age of presentation of individuals with familial TAAD is younger than that of individuals with non-familial TAAD but older than mean age of presentation of individuals with Marfan syndrome [Coady et al 1999]. Aortic dissection is exceedingly rare in early childhood but aortic dilatation may be present in childhood.

In most adults, the risk of aortic dissection or rupture becomes significant when the maximal aortic dimension reaches about 5.5 centimeters; individuals with TGFBR2 mutations may dissect prior to enlargement to 5.0 cm [Loeys et al 2005; Milewicz, unpublished data].

A minority of affected family members present with dissections of the descending aorta. It does not appear that enlargement of the descending aorta precedes these descending aorta dissections.

Life expectancy

With proper management, including medical therapy and prophylactic repair of aneurysmal dilatation, the life expectancy of an individual with a thoracic aortic aneurysm should approach that of the general population. It is assumed that those family members who are screened because of family history will have a better prognosis than relatives ascertained as a result of dissection.

References