Heart rate variablity indices are poor predictors of exercise capacity in healthy type 1 diabetics (LB664)

Abstract

People with diabetes often have chronotropic incompetence and reduced exercise tolerance. Chronotropic incompetence has been associated with autonomic dysfunction, thus we determined the ability of resting heart rate variability (HRV) to predict an altered exercise response in healthy individuals with type 1 diabetes (T1D). Baseline measures were taken followed by quantification of HRV with power spectral analysis during controlled breathing (15 breaths·min‐1) in 20 T1D (10 male & 10 female) screened for ischaemic cardiac disease and 12 age‐, weight‐, and training‐matched non‐diabetics (CON: 7 male & 5 female). These measurements were followed by a VO2max test (with ECG). Resting HR (73 ± 10 vs. 64 ± 10 beats·min‐1; P = 0.01) was higher and mean arterial blood pressure (92 ± 12 vs. 90 ± 11 mm Hg; P = 0.68) was not different between T1D and CON respectively. HR reserve (104 ± 17 vs. 121 ± 11 beats·min‐1; P < 0.001), VO2max (31 ± 9 vs. 41 ± 9 mL·min‐1·Kg‐1; P =0.005), HRV total power (1317 ± 1146 vs. 7493 ± 15080 ms2; P = 0.024), and HRV high frequency power (441 ± 491 vs. 3840 ± 9883 ms2; P = 0.029) were lower in T1D vs. CON respectively. Absolute max HR (177 ± 15 vs. 185 ± 10 beats·min‐1; P = 0.09), % of age predicted max HR (95 ± 6 vs. 97 ± 2 %; P = 0.07), and HRV low frequency power (328 ± 279 vs. 1672 ± 3433 ms2; P = 0.09) were not different in T1D vs. CON respectively. Despite group differences in HRV, linear correlations showed that resting HRV total, high frequency, and low frequency power accounted for < 20% of the variability in resting HR, HR reserve, max HR, and VO2max in T1D. Resting HRV indices are poor predictors of cardiovascular exercise response in healthy T1D.Grant Funding Source: Supported by Anderson's trust