LEFT VENTRICULAR OUTFLOW TRACT OBSTRUCTION
Left ventricular outflow tract obstruction can occur at the valvular, subvalvular, or supravalvular levels, isolated or at multiple levels.
VALVULAR AORTIC STENOSIS
The most common cause for congenotal valvular aortic stenosis is bicuspid aortic valve. Mutations in the NOTCH 1 gene have been related to bicuspid aortic valve. Abnormalities of the aortic wall which are associated with bicuspid aortic valve can lead to progressive dilatation, aortic aneurysm, rupture or dissection.
Patient frequently remain asymptomatic for many years. Progression of stenosis varies and depends on initial severity, degree of calcification, age and atherosclerotic risk factors, In bicuspid aortic valve, progression is faster in those patients with greater closure line eccentricity and an anteroposterior-oriented line of closure.
prognosis is good and sudden death is rare in asymptomatic patients with good exercise tolerance, even when stenosis is severe. Once symptoms (angina pectoris, dyspnoea or syncope) occur the prognosis deteriorates rapidly.
Symptomatic patients require urgent surgery. Medical treatment for heart failure is reserved only for non-operable patients. Neither statin treatment nor any other medical treatment has so far been shown to retard progression of aortic stenosis.
SUPRAVALVULAR AORTIC STENOSIS
Supravalvular aortic stenosis can occur either as a localized fibrous diaphragm just distal to the coronary artery ostia or, most commonly, as an external hourglass deformity with a corresponding luminal narrowing of the aorta, or as diffuse stenosis of the ascending aorta. It fequently occurs as part of the Williams-Beuren syndrome, and may be associated with hypoplasia of the entire aorta, involvement of coronary ostia or stenosis of major branches of the aorta or pulmonary arteries.
Patients present with symptoms of either outflow obstruction or myocardial ischaemia. Sudden death occurs rarely, but it is more common in supra aortic stenosis with Williams-Beuren syndrome, with diffuse peripheral pulmonary artery stenosis, or with coronary artery disease. Surgery is the primary treatment.
Subaortic stenosis can occur as an isolated lesion, but is frequently associated with a ventricle septal defect, an atrioventricular septal defect, or Shone complex, or may develop after correction of these lesions. It caused by a fibrous ridges in the left ventricular outflow tract proximal to the aortic valve or as fibromuscular narrowing and has to be differentiated from hypertophic cardiomyopathy.
The clinical course is highly variable. Aortic regurgitation is frequent but rarely haemodynamically significant or progressive.
Surgical treatment involves a circumferential resection of the fibrous ring and parts of the muscular base along the left septal surface.