Biopsied myocardial tissue was obtained from 24 patients electing coronary arterial bypass surgery who were divided into three groups: chemical diabetics (CD) with normal fasting blood sugar levels and incidentally encountered elevated glucose levels after sugar loading; overt diabetics (OD) requiring insulin treatment; and euglycemic, nondiabetic patients (ND) serving as a control group. Specimens from the left anterior apical segment of the heart were processed for ultrastructural examination, with special emphasis on determining capillary basal laminar thickness with the aid of morphometric techniques.

Results of this study indicate that (1) a statistically significant increase in basal laminar thickness is evident in myocardial tissue of OD patients; (2) incipient alterations in laminar width are demonstrable in the CD group; (3) the predominant morphologic abnormalities, which we have examined in the parenchymal tissue of the biopsied hearts, namely myocardial hypertrophy and interstitial fibrosis, are present to a comparable degree in all three groups of patients; and (4) the average thickness of basal laminae around myocardial capillaries tends to be narrower compared with measurements reported in other tissue compartments.

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