Bicuspid aortic stenosis pathophysiology


 * Associate Editor-In-Chief:

Overview
A congenital bicuspid aortic valve may be associated with the development of either progressive clacific stenosis or regurgitation. What differentiates the pathophysiology of bicuspid aortic stenosis from other forms of aortic stenosis such as the degenerative aortic stenosis is the presence of concomitant valve disease, aortic root disease, and an increased incidence of coarctation of the aorta.

Pathophysiology of Aortic Stenosis
The pathophysiology of aortic stenosis is described in the main chapter on the pathophysiology of aortic stenosis here. What differentiates the pathophysiology of bicuspid aortic stenosis from other forms of aortic stenosis such as the degenerative aortic stenosis is the presence of concomitant valve disease, aortic root disease, and an increased incidence of coarctation of the aorta.

Incidence of Concomitant Valve Disease

 * Only 25% of patients with congenital aortic stenosis (AS) have aortic insufficiency (AI) compared with 75% of cases with acquired AS.
 * In 75% of those with acquired AS, there is associated mitral valve disease. This association is rare in congenital AS.

Concomitant Disease of the Aorta
The aorta of patients with bicuspid aortic valve does not have the same histological characteristics of a normal aorta. The tensile strength is reduced. These patients are at a higher risk for aortic dissection and aneurysm formation of the ascending aorta. The size of the proximal aorta should be evaluated carefully during the evaluation of the patient for aortic stenosis surgery. The initial diameter of the aorta should be noted and periodic evaluation with CT scan (every year or sooner if there is a change in aortic diameter) should be recommended. Therefore, if the patient needs surgery, the size of the aorta will determine what type of surgery should be offered to the patient.

Associated Congenital Heart Disease
Patients with bicuspid aortic valve are also at higher risk of aortic coarctation, an abnormal narrowing of the thoracic aorta.

Gross Pathology
Gross pathologic evaluation in patients with bicuspid aortic stenosis demonstrates fusion of one of the three commisures which results in two functional leaflets instead of the usual three aortic leaflets. Left ventricular hypertrophy is present in bicuspid aortic stenosis.

Pathological Findings
Images shown below are courtesy of Professor Peter Anderson DVM PhD and published with permission.