EXERCISE RESPONSES IN PATIENTS WITH IDDM

OBJECTIVE - The hemodynamic, respiratory, and metabolic responses to e xercise were studied in IDDM patients and control subjects to detect d iabetic cardiomyopathy. RESEARCH DESIGN AND METHODS - Eight subjects a ged 25-40 years with diabetes of at least. 10 years' duration were com pared with eight control subjects aged 21-46 years. All subjects under went a progressive incremental bicycle exercise test with measurement of gas exchange, blood glucose, lactate, fat metabolite, and catechola mine levels and two steady-slate exercise tests with measurement of ca rdiac output by a CO2 rebreathing method. A new first-pass radionuclid e method was used to measure cardiac ejection fractions (EFs) at rest, peak exercise, and steady-state exercise. RESULTS - The peak achieved oxygen consumption was similar in the diabetic and control subjects ( 29.9 [25.1-34.6] and 31.4 [26.9-35.9] ml . min(-1) . kg(-1), respectiv ely; mean [95% Cl). There were no significant differences in heart rat e, double product, ventilation, respiratory exchange ratio, or ventila tory equivalents for oxygen and CO2 during the incremental test. Gluco se levels were higher in the diabetic subjects, but there were no sign ificant differences in levels of lactate, catecholamines, free fatty a cids, glycerol, or beta-hydroxybutyrate. Left ventricular EF fell from rest to peak exercise within the diabetic group (66.0% [59.6-72.4] at rest; 53.6% [45.6-61.6] at peak; P < 0.05) but this did not differ si gnificantly from the control group (58.7% [52.3-65.1] at rest; 60.3% [ 48.9-71.7] at peak). Right ventricular EFs were similar in each group, and there was no reduction in peak filling rate to suggest diastolic dysfunction. The cardiac output responses to exercise were also simila r in the two groups. CONCLUSIONS - There is no evidence of impairment of the exercise response in subjects with long-standing diabetes, and the apparent fall in left ventricular EF at peak exercise could be rel ated to hemodynamic adaptation.