First application of coronary flow reserve measurement for the assessment of left main compression syndrome in pulmonary hypertension.

Left main compression syndrome (LMCS) refers to extrinsic compression of the left main coronary artery because of a dilated pulmonary artery trunk. The condition represents an unusual cause of angina, left ventricular dysfunction, and sudden cardiac death in patients with pulmonary hypertension. We present 2 patients with the syndrome who were followed with serial assessments of coronary flow reserve by transthoracic echocardiography to screen for LMCS-related ischemia.