BackgroundEvaluation of heart rate variability (HRV) detects the early subclinical
alterations of the autonomic nervous system. Thus, impaired HRV is the earliest subclinical
marker of cardiac autonomic neuropathy (CAN) in type 1 diabetes mellitus (T1DM).ObjectivesWe
aimed to explore the HRV parameters in asymptomatic T1DM patients and compare them
with the results obtained in healthy subjects. Potential associations between HRV
parameters and the established risk factors for CAN and cardiovascular diseases were
also investigated.MethodsSeventy T1DM patients (38 ± 12 years, 46 females)
and 30 healthy subjects were enrolled into the study. For HRV analysis, beat-to-beat
heart rate was recorded for 30 min. The less noisy 5-min segment of the recording
was analyzed by Bittium Cardiac Navigator HRV analysis software. Time domain, frequency
domain, and nonlinear indices were calculated.ResultsRegarding ratio of
low to high frequency component (LF/HF), no differences were found between the two
populations (p = 0.227). All the further, time domain, frequency domain, and nonlinear
HRV indices were significantly lower in T1DM patients (each p < 0.001). In multiple
linear models, disease duration remained the only independent predictor of LF/HF ratio
(p = 0.019). HbA1c was found to be significant independent predictor of all further
time domain (SDNN, p < 0.001; rMSSD, p < 0.001), frequency domain (VLF, p < 0.001;
LF, p = 0.002; HF, p = 0.006; Total Power, p = 0.002), and nonlinear indices (SD1,
p = 0.006; SD2, p = 0.007), alone, or in combination with other factors, such as age
or body mass index.ConclusionAsymptomatic T1DM patients have significantly
reduced overall HRV as compared with healthy subjects, indicating subclinical CAN.
Quality of the glycemic control is important determinant of HRV among T1DM patients.
This relationship is independent of other risk factors for CAN or cardiovascular diseases.
