Attenuated fast heart rate recovery suggests delayed parasympathetic reactivation after cessation of exercise in uncomplicated type 1 diabetes patients

Heart rate recovery (HRR) and fast HRR, believed to reflect parasympathetic reactivation, have been recognized as powerful predictors of all-cause mortality. In this study we propose a modified fast HRR parameter T30HRR and investigate if otherwise healthy subjects with type 1 diabetes (T1D) have attenuated HRR. Eighteen T1D subjects (T1D = 15 ± 7 years, HbA1c = 58 ± 0.8 mmol/mol) and thirty-five healthy matched control subjects underwent maximal cardiopulmonary exercise test. After cessation of exercise T30, T30HRR and monoexponential decay as well as HRR at 10, 20, 30, 60, 120 and 300 s were assessed. The T1D subjects had diminished HRR described by T30HRR (12.6 ± 3.9 bpm vs. 16.4 ± 4.3 bpm, p = 0.013), T30 (520 ± 263 s vs. 361 ± 133 s, p = 0.022), HRR20 (9.2 ± 3.5 vs. 11.6 ± 3.1 bpm, p = 0.046), HRR30 (13.0 ± 4.5 bpm vs. 16.3 ± 4.2 bpm, p = 0.035) and HRR60 (23.0 ± 6.8 bpm vs. 28.4 ± 7.1 bpm, p = 0.041) when compared to the control subjects. Subjects with T1D exhibited attenuated fast HRR suggesting that vagal reactivation may be diminished, and exercise may unmask subclinical symptoms in otherwise healthy T1D subjects.