Cardiac Autonomic Neuropathy (CAN) is a common underdiagnosed complication of type 2 diabetes (DT2). Heart Rate Variability (HRV) at rest, in the time and frequency-domain, has been shown to effectively diagnose CAN. Post-exercise recovery period is associated with changes in parasympathetic and sympathetic control, allowing potential identification of autonomic alterations that are not evident in resting condition.

To compare resting and post-exercise recovery HRV frequency variables in DT2 patients with and without CAN and control participants.

Thirty-six DT2 patients and 12 control participants (CG) were included. DT2 were divided in DT2 with CAN (CAN+; n=14) and without CAN (CAN-, n=22) based on cardiovascular autonomic reflex tests. All subjects performed the six-minutes walking test (6MWT). HRV analysis was assessed during 5minutes in time and frequency domain (Total Power Spectrum (TP), Low-Frequency (LF), High Frequency (HF), LF/HF ratio) at rest and post-exercise. Statistical comparisons between groups were performed by one-way and repeated measure ANOVA.

CAN+ and CAN- performed lower distance to 6WMT than CG (401±98; 449±76; 541±65m, respectively P<0.001) despite similar exercise intensity. At rest, TP was lower in CAN+ and CAN- than CG (105±75; 407±290 and 1300±1197ms², respectively P<0.001) with lower value in CAN+ than CAN-. No significant differences in normalized LF and HF were noted between groups. During recovery, TP decreased in CG whereas it increased in CAN+ and did not change in CAN-. Normalized LF and LF/HF ratio increased significantly while normalized HF decreased in the three groups with no difference between groups.

The different TP changes from rest to recovery between groups were not associated with different changes in LF and HF components. Further LF and HF post-exercise kinetics analysis will be necessary to explain the underlying mechanisms.