Impaired cardiac parasympathetic control in healthy young people with type 1 diabetes (LB658)

Diabetes reduces heart rate (HR) reserve during maximal exercise. We measured HR during a low- and high-dose (0.1 and 0.4 mg·kg-1) atropine bolus followed by incremental dobutamine infusions (5 - 40 μg·kg-1·min-1) up to 85% maximal HR to determine the roles of the parasympathetic and sympathetic nervous system in the diabetic HR response. Five 18 – 30 year old individuals with type 1 diabetes (T1D), but without cardiovascular disease or hypertension and four age-, sex- and training-matched non-diabetic subjects (CON) performed a VO2max test (with ECG) on a cycle ergometer. On a second day, parasympathetic control was determined by comparing the change in HR during atropine doses using ANOVA. Sympathetic responsiveness was compared using the slope of the change in HR (after high-dose atropine) across dobutamine infusion rates. VO2max and maximal HR during the exercise test were the same between groups (P > 0.05). Resting HR was greater in the T1D vs. CON (75 ± 4 vs. 62 ± 6 beats·min-1; P < 0.05). Heart rat...