Extrinsic compression of the left main coronary artery by a dilated pulmonary artery: Clinical, angiographic, and hemodynamic determinants

Extrinsic compression of the left main coronary artery (LMC) by the pulmona ry artery (PA) is a very unusual and poorly understood entity, usually asso ciated with the presence of adult congenital heart disease. We identified 1 2 patients (age range, 6 months to 55 years) with LMC stenosis (greater tha n or equal to 50%) presumably secondary to compression by a dilated main PA and related to various forms of heart disease (11 congenital, 1 pulmonary hypertension). In all cases, the main PA was dilated with the main PA/aorti c root diameter increased (mean, 2.0; normal value, less than or equal to 1 .0), and in all but two, PA pressures were increased (> 30 mm Hg systolic). Left coronary trunk stenosis was usually visualized in only one angiograph ic view (best seen in 45 degrees left anterior oblique, 30 degrees cranial projection). The LMC also appeared to be inferiorly displaced and in close contact with the left aortic sinus (mean angle between sinus and LMC was 23 degrees +/- 13 degrees, a control group was 70 degrees +/- 15 degrees). In one patient, surgical correction of the dilated PA was associated with a r eduction in LMC stenosis from 85% to < 50% and less inferior left main disp lacement (from 25<degrees> to 50 degrees). Patients with a dilated main PA may exhibit extrinsic LMC compression leading to significant eccentric narr owing and downward displacement of the LMC. In the presence of significant dilatation of the main PA from any etiology, functional and/or anatomic stu dies should be performed to exclude significant LM obstruction. Cathet Card iovasc Intervent 2001;52:49-54. (C) 2001 Wiley-Liss, Inc.