To evaluate lesions of the left main coronary artery (LM) in the aged, a pathologic study was performed on a total of 972 consecutive autopsy cases over 60 years of age. The study population consisted of 503 men and 469 women with an average age at death of 79.0 years. In this study the degree of narrowing and length of the LM were evaluated in all cases (T), and the 141 cases with normal hearts (N) were compared with the 202 cases with myocardial infarction (MI).
The following results were obtained: (1) the average coronary stenotic index (CSI) was 9.1/15 in T, 5.8/15 in N and 11.2/15 in MI (N<MI, p<0.001), (2) the grade of narrowing in the LM (LMG), when 100% obstruction of the LM is counted as 5, was 1.8±0.9 in T, 1.3±0.6 in N and 2.3±1.1 in MI (N<MI, p<0, 001). Cases showing more than 75% narrowing of the LM were found in 58 (6%), of which 35 cases belonged to MI, but development of MI directly due to lesions in the LM was found in only 9 patients (4.5% among MI), (3) the average length of the LM (LML) was 9.4±4.4mm in T, 9.0±4.2mm in N and 9.3±3.8mm in MI (N vs MI; n.s.). Cases presenting left coronary artery dominance (n=82) or a balanced type (n=159) showed shorter LML than those with right coronary artery dominance (n=729) (8.5±4.0mm, 8.8±4.6mm and 9.7±4.4mm, respectively, p<0.05), (4) in T there was a correlation between the LMG and CSI, but not between the LML and CSI. In conclusion, lesions of the LM in the aged were generally mild and the LMG showed a positive correlation with CSI and the narrowing of each coronary branch, while no relationship was noted between the LML and CSI.