A 38-year-old man symptomatic with exertional dyspnoea (NYHA III) and angina (CCS II) was diagnosed with hypertrophic obstructive cardiomyopathy. Transthoracic echocardiography (Panel A.1. parasternal long-axis view, A.2. short-axis view) demonstrated pronounced asymmetric septal hypertrophy (septal wall thickness 31 mm) with supranormal left ventricle systolic function (ejection fraction 80%), resting systolic anterior motion of mitral valve, left ventricle outflow tract (LVOT) obstruction with a peak rest gradient 19 mmHg and 76 mmHg after provoking test and an unusual finding of the mitral valve resembling a trefoil, which we called "a trefoil sign".
It is caused by a redundant tissue of the anterior leaflet of the mitral valve