Abstract
It is well recognized that diabetic subjects have a higher incidence of myocardial infarction (MI) than non-diabetic subjects. However, the exact pathogenesis of this finding has not hitherto been described. It has been reported that changes similar to diabetic microangiopathy were found in intramyocardial coronary artery branches (IMCAB). On the other hand, investigations performed in author's laboratory have clarified morphological changes of IMCAB, suggestive of hemodynamic derangement in non-diabetic infarcted hearts, which may indicate the importance of peripheral circulatory disturbance in the development of MI.
In order to discuss the relationship between diabetes mellitus (DM) and MI, histopathological changes of main coronary artery stems (MCAS), IMCAB and myocardium were examined light microscopically in 60 cases and electron microscopically in 10 cases in diabetic autopsied hearts with MI and without MI (30 and 30 cases respectively).
The results obtained are as follows :
1) In diabetics with MI, the findings of MCAS and IMCAB were similar to those previously obtained in non-diabetic patients with MI, and were not specific to DM per se.
2) In diabetics without MI, the MCAS showed severe intimal and medial impairment at the same site as where thrombi had been frequently detected in infarcted heart.
In IMCAB, like those of infarcted hearts, acute changes such as endothelial cell destruction, imbibition of serum components into the subendothelial spaces, and cytolytic changes of medial muscle cells were present, in addition to the remote changes including thickening and fragmentation of subendothelial basement membrane with increase of collagenous fibrils, in spite of the fact that the MCAS remained to be impaired to lesser extent. These acute and old changes of the IMCAB were frequently accompanied with interstitial fibrosis, and justified as the preceding involvement of the MCAS.
In conclusion, these findings obviously suggest the presence of severe repetitive derangement in the intramyocardial peripheral circulation which might be caused by superimposed pathological incidences in DM. The higher incidence of myocardial infarctions in the diabetic subjects may be explained on this theoretical basis.
