Abstract
Abnormal heart function in diabetics and diabetic cardiomyopathy have recently been described but their pathogenesis and relationship to microangiopathy have not yet been clarified. In order to determine the cause of abnormal heart function in diabetics, studies on ultrasonic and pathologic changes were made.
A Toshiba Sonolayer 11 A with a 2.25 MHz focused transducer and strip chart recorder were used for ultrasonic cardiography (UCG) to measure the interventricular septal thickness (IVST), posterior wall thickness (PWT), ejection fraction (E.F.) and stroke index (S.I.). Autopsied hearts after formalin fixation were subjected to IVST/PWT measurements and histologic studies. High contrast pictures of the H.E.-stained heart septum and anterior wall were analyzed using a Quantimet 720 Image Analyzing Computer (Cambrige Instruments). The diameters of the heart muscle fibers were also estimated.
The UCG studies revealed that the ratio of the interventricular septal thickness (IVST) to posterior wall thickness (PWT) in diabetics was significantly larger than that in controls (p<0.005), and that of diabetics with microangiopathy (1.10 ± 0.04) was significantly larger than that of those without microangiopathy (0.94 ± 0.04), (p<0.01). The E.F. and S.I. were significantly decreased in the diabetes-with-microangiopathy group, suggesting decreased heart function.
Postmortem studies confirmed the above findings and the diameters of the muscle fibers in diabetics (12.9 ± 0.1 μm) were significantly smaller than those in controls (14.4 ± 0.1μm), (p<0.005).
Gradual narrowing of the small coronary vessels (e.g. diffuse coronary microangiopathy) is thougtht to cause a mild degree of diffuse myocardial ischemia, which tends to induce cardiac dilatation and hypertrophy. Increase in the interstitial space and atrophy of myocardial fibers may derive from chronic myocardial ischemia and a decrease in the excretion of metabolites.
The present ultrasonic and pathologic studies suggest that the thickness of the septum is increased in diabetics and this might be related to microangiopathic changes.
