Exercise testing with myocardial scintigraphy in asymptomatic diabetic males

Abstract

Sixteen diabetic males, 32-60 years old (mean 48.7 ± 8.9 years), without clinical or electrocardiographic evidence of heart disease and 12 normal volunteers, mean age 48.9 ± 8.8 years, participated in maximal exercise testing combined with thallium-201 myocardial scintigraphy. A motorized treadmill was used with the Bruce protocol. A standard 12-lead ECG and systolic blood pressures were recorded every minute during exercise and for at least 8 minutes in the postexercise period. Echocardiograms were obtained at rest for chamber dimensions and myocardial function. At maximal stress the heart rate attained by the normal controls was higher (174.5 ± 17.4 beats/min) than that of the diabetic males (163.1 ± 9.9 beats/min) (p<0.05). Although the maximal systolic blood pressure for both groups was comparable (215.9 ± 32.5 mm Hg for the diabetics vs 209.6 ± 21.6 mm Hg for the normal controls), maximal systolic blood pressures > 210 mm Hg occurred in only three of 12 normal subjects (25%) but was noted in nine of 16 diabetics (56.2%). The duration of exercise was longer in controls (663.0 ± 92.1 seconds) than in the diabetics (519.9 ± 126.2 seconds) (p<0.005). The estimated maximal oxygen consumption was also increased in controls vs diabetics (p<0.005). Functional aerobic impairment was greater in the diabetics (10.4 ± 19.1%) compared with normal controls (-7.8 ± 9.0%). Significant ST-segment changes were present in two diabetics and one control subject. Of the 12 diabetic subjects who underwent exercise testing with thallium-201, five (41.7%) had abnormal perfusion during stress or with both stress and rest. Such abnormalities were present only once in the 11 perfusion studies in healthy subjects. Echocardiographic findings were similar in both groups. However, the percent of myocardial fractional shortening was smaller in diabetics than in controls (p<0.05). Of the 12 subjects who underwent myocardial scintigraphy, an abnormal exercise ECG or a myocardial perfusion defect appeared in seven (58.3%) of the diabetics without overt cardiac disease and in only one normal subject. This suggests that asymptomatic subjects in this high-risk category of middle-aged diabetic males should be under close and repeated surveillance.