Heart rate turbulence in patients with poorly controlled diabetes mellitus type 2

Cardiac autonomic neuropathy (CAN) causes substantial morbidity and increased mortality in patients with diabetes mellitus (DM). Besides heart rate variability (HRV), heart rate turbulence (HRT) is an important method of assessment of cardiac autonomic regulation. The aim of the study was to assess the correlation between HRT and diabetic control.

Fifty-nine patients met the inclusion criteria - 38 males and 21 females, age 64.4 ±7.6. The patients included had inadequately controlled DM type 2 defined as glycated haemoglobin (HbA1c) > 9% (mean 11.8 ±2.7%). In all patients, intensive insulin treatment had been applied for 6 months. After 6 months, HbA1c was measured. ECG Holter monitoring was performed before and after insulin treatment to evaluate the time domain HRV and HRT parameters (turbulence onset (TO) and turbulence slope (TS)).

After 6 months of intensive insulin treatment, HbA1c concentrations ranged from 6.3% (45 mmol/mol) to 11.2% (99 mmol/mol) - mean 8.5 ±3.8% (69 ±18 mmol/mol). Significant improvement of TO, TS and SDNN was observed. The TO and TS significantly correlated with HbA1c (r = 0.35, p = 0.006 and r = -0.31, p = 0.02 respectively). Among analyzed HRV time domain parameters such as SDNN, rMSSD and pNN50, only SDNN correlated with HbA1c (r = -0.41, p = 0.001). It was further concluded that intensive insulin therapy led to better glycemic control, resulting in improvement of HRT.

Heart rate turbulence may be useful in monitoring changes of the autonomic nervous system functions in patients with DM, similarly to HRV parameters.