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Left ventricular outflow tract (LVOT) obstruction (LVOTO): The Role of CT in TAVR and in TMVR

Reporter: Aviva Lev-Ari, PhD, RN

Left ventricular outflow tract obstruction (LVOTO) is a recognised feature of this condition which arises when blood leaving the outflow tract is impeded by systolic anterior motion of the mitral valve. LVOT obstruction was defined as a resting LVOT gradient of ≥30 mm Hg, with severe obstruction defined as ≥50 mm Hg (15).

Left ventricular outflow tract (LVOT) obstruction can occur at the valvular, subvalvular, or supravalvular level. In general, there is an obstruction to forward flow which increases afterload, and if untreated, can result in hypertrophy, dilatation, and eventual failure of the left ventricle. In the United States, most cases of LVOT obstruction are congenital in individuals younger than 50 years of age.

Watch the VIDEO “What to Look for in CT Structural Heart Planning Software.”

Issues of Concern

Common Causes of Left Ventricular Outflow Tract Obstruction

Subaortic Stenosis (SAS)

Subaortic stenosis is narrowing at the level of the aortic valve. It may be due to a discrete ridge or fibrous ring encircling the LVOT. This fibrous membrane may extend onto the aortic valve cusps and make contact with the ventricular side of the anterior mitral leaflet. The obstruction may be focal or more diffuse, resulting in a tunnel leading out of the left ventricle. The discrete form is most common. Complex subaortic stenosis can also be seen which leads to abnormal adherence to the anterior leaflet of the mitral valve to the septum and the presence of endocardial tissue in the LVOT. These type of obstructions are commonly seen in patients with ventral septal defects (VSDs).

Clinical Significance

Left ventricular outflow tract obstructions involve stenotic lesions starting in the anatomic left ventricular outflow tract and stretching to the descending portion of the aortic arch.

Obstruction can be valvar, subvalvar, or supravalvar. Obstructions to forward flow can present alone or in concert. All of these lesions result in increased afterload on the left ventricle and if severe, result in hypertrophy and eventual dilatation and failure of the left ventricle. These lesions are usually congenital in the vast majority of individuals younger than 50 years. All patients with left ventricular outflow tract obstruction at a high risk for developing infective endocarditis and prophylaxis should be instituted.

Bicuspid Aortic Valve (BAV)

Bicuspid aortic valve is one of the most common congenital cardiovascular malformations, present in about 1% to 2% of the population and more common in males. BAV can be inherited, and family clusters have been documented. In those cases, inheritance patterns are usually autosomal dominant with variable penetrance. A mutation in the NOTCH1 gene has also been described.

BAVs arise from abnormal vasculogenesis and cusp formation, resulting in the formation of 1 smaller cusp and one larger cusp. More commonly, the right and left coronary cusps are fused. BAV is usually progressive, and most valves function normally until later in life. The abnormal valve formation leads to increased leaflet stress, more turbulent flow and restricted motion which leads to accelerated valve changes including scarring, calcification, aortic stenosis, and regurgitation. BAV is associated with dilation of the ascending aorta and increased risk of aortic dissection.

Clinical Features

The most common complication of BAV is aortic stenosis.

SOURCE

Left Ventricular Outflow Tract Obstruction

Viliane Vilcant; Ofek Hai.

https://www.ncbi.nlm.nih.gov/books/NBK470446/