The purpose of this study was to analyze the cardiac function of diabetic patients. The cardiac index, using the CO2 rebreathing technique, was determined at rest and after exercise in 20 diabetic patients (NIDDM: 17 males and three females) and in five healthy volunteers as a control (five males). No abnomalities on the electrocardiogram were found in any of the patients either at rest or after exercise.
The results were as follows: 1) In comparison with the control group, there was a significant reduction of the increase in the ratio of the cardiac index in diabetics. 2) This reduction of the increase in the ratio of the cardiac index was recognized in diabetics without any other diabetic complications. 3) These phenomena were in accordance with the degree of diabetic retinopathy.
In conclusion, cardiac dysfunction of diabetic patients during exercise was recognized even in the early stage of diabetes mellitus. This was thought to reflect a decrease in cardiac reserve. Cardiac dysfunction is considered to occur as a result of the following factors: a) abnormalities of contractile protein of the heart muscle; b) metabolic disturbance and c) the structural abnormalities of capillaries in the human diabetic heart as we have already reported.
