Adult congenital heart disease: left-sided obstructive lesions

### Learning objectives Congenital obstruction of the left heart encompasses a range of stenotic lesions that can occur in isolation or as a series of multilevel obstructions. Left ventricular outflow tract (LVOT) defects typically include subaortic stenosis (SubAS), valvular aortic stenosis, supravalvular aortic stenosis (SupAS) and coarctation of the aorta (CoA). They are often associated with other congenital anomalies, including left-sided obstruction due to left atrial obstruction or congenital mitral stenosis. The constellation of a series of left-sided obstructive lesions, including supravalvular mitral ring (SVMR), parachute mitral valve, SubAS, CoA, and bicuspid aortic valve (BAV), is known as the Shone syndrome. Shone syndrome is rare, with only case reports and small case series published. This article is intended as a contemporary review of the causes, manifestations, treatments and outcomes of left-sided obstruction in the context of a patient with adult congenital heart disease (ACHD). Obstruction to left ventricular inflow leads to higher atrial filling pressures and can predispose to pulmonary oedema. Chronic elevation in atrial filling pressures leads to elevated pulmonary venous pressures. Over time, chronic pulmonary venous hypertension results in pulmonary vascular remodelling, and pulmonary arterial hypertension can develop (WHO group II pulmonary hypertension). Obstruction to left ventricular outflow causes a pressure load on the left ventricle, leading to adverse remodelling and hypertrophy as compensation. However, the increase in ventricular mass over time may be insufficient to offset wall stress, resulting in left ventricular systolic dysfunction and decreased cardiac output.1 Chronic pressure load also causes diastolic dysfunction and myocardial damage. Some studies suggest that the proximity of the obstruction to …