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

Abstract

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 T30_HRR 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, T30_HRR 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 T30_HRR (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.

Keywords: CPET; Diabetes; Heart rate recovery; Neuropathy; Parasympathetic reactivation; T30HRR.

Fig. 1

An example of the fitted monoexponential function over the recovery period (panel a) and the steepest slope for the T30_HRR parameter in the first 40-seconds of the recovery period (panel b).

Fig. 2

HRR parameters on individual level for control (CON) and T1D (DM) subjects. HRR parameters are presented on separate panels: T30 (a), T30_HRR (b), HRR₁₀ (c), HRR₂₀ (d), HRR₃₀ (e), HRR₆₀ (f), HRR₁₂₀ (g), HRR₃₀₀ (h), and HR_decay (i).