Effect of variation in coronary artery anatomy on distribution of stenotic lesions.

A relation between the proximal or distal localisation ofatherosclerotic lesions and 3 anatomical variables (i) the length of the left main coronary artery, (ii) its angle of bifurcation into anterior descending and circumflex arteries, and (iii) the dominant coronary artery, was sought at coronary angiography. Studies were made on 149 angiograms of which 95 had critical stenoses (>50% of vessel lumen) and the remaining 54 were either normal or contained only minimal disease. The mean left main coronary artery length was shorter in the patients with coronary artery disease (10.6 mm) than in the normals (12.9 mm). Patients with proximal coronary artery disease (9.1 mm) had a much shorter mean left main coronary artery length than those with distal lesions alone (12.9 mm). This finding implies that a short left main coronary artery favours the proximal localisation of atherosclerotic stenoses by increasing the severity of atherogenesis proximally. No significant difference was found between the mean angle of bifurcation of the normals (750) and that of the total coronary artery disease group (810). The patients with proximal disease showed a tendency towards a wider bifurcation angle (850) than the distal disease group (760) but this did not reach significance at the 5 per cent level. When present in combination with a short left main coronary artery, a wide bifurcation angle was associated with a trend towards proximal localisation of stenoses over and above that of a short left main coronary artery alone. Dominant circumflex systems had significantly shorter mean left main coronary artery lengths (9.1 mm) than had dominant right coronary arteries (12-0 mm). No effect of circumflex dominance on localisation of disease was found. These results show that a short left main coronary artery alone constitutes an anatomical factor which favours proximal localisation of stenoses. This effect is further enhanced by its combination with a wide angle of bifurcation.