EXERCISE ELECTROCARDIOGRAPHY AND AORTIC DOPPLER VELOCIMETRY IN ASYMPTOMATIC IDENTICAL-TWINS DISCORDANT FOR TYPE-1 (INSULIN-DEPENDENT) DIABETES

Objective-To determine the influence of insulin dependent diabetes on the prevalence of myocardial ischaemia and on global left ventricular systolic performance. Design-Stress treadmill electrocardiograms and s imultaneous Doppler measurement of aortic maximum acceleration were ob tained during exercise on symptom free subjects. The electrocardiogram s were scored blindly according to the Minnesota code. Participants-39 identical twin pairs (22 male) discordant for insulin dependent diabe tes and 39 non-diabetic controls of similar age and sex were examined. The twins and controls had a mean age of 37 (range 25-69) with a mean (SD) duration of diabetes in the diabetic twin of 17 (7) years. Those selected were normotensive and had no renal impairment. Results-Systo lic blood pressure was significantly higher in the diabetic twins than in their non-diabetic cotwins both at rest (p < 0.05) and at peak exe rcise (p < 0.01). Electrocardiographic evidence of ischaemia was not c orrelated within twin pairs and was found in similar numbers of diabet ic twins, their non-diabetic cotwins, and control subjects. Abnormal e lectrocardiograms were found in a similar number of diabetic twins (23 %), non-diabetic cotwins (18%), and controls (15%). There was a signif icant correlation in Doppler measurements of global left ventricular s ystolic function within the identical twins; no significant difference was found for these Doppler measurements in the diabetic twins, non-d iabetic cotwins, or controls. Conclusion-Exercise characteristics and cardiac function seem to be subject to shared genetic or shared enviro nmental influences or both, whereas electrocardiographic features of i schaemia seem to be environmentally determined. In a selected cohort o f diabetic identical twins without evidence of nephropathy there was n o evidence that diabetes influenced the prevalence of myocardial ischa emia or global left ventricular systolic function.