Vol 7, No 6 (2006): Practical Diabetology
Research paper
Published online: 2006-10-18
The relation between time- and frequency-domain measures of heart rate variability, QT interval and dispersion, JT interval and corrected JT in patients with type 1 diabetes
Diabetologia Praktyczna 2006;7(6):382-389.
Abstract
BACKGROUND. Patients with diabetes complicated by cardiovascular autonomic neuropathy (CAN) are at risk of cardiac arrest as the result of life-threatening cardiac arrhythmia. In CAN, due to sympathetic and parasympathetic imbalance, heart rate variability
(HRV) and electrical stability of the heart are reduced.
AIM OF THE STUDY. The aim of the study was to analyze time- and frequency-domain HRV in patients with type 1 diabetes and their relation with ventricular repolarization parameters: QT and JT, corrected QT and JT, and dispersion of the parameters.
MATERIAL AND METHODS. We studied 17 patients with CAN based on at least two Ewing tests and 17 patients without CAN (age: 37.76 ± 11.78 and 31.65 ± 7.98, diabetes duration 22.06 ± 10.26 and 11.94 ± 10.36 years). In all subjects we measured time- and frequency-domain components of HRV; QT and JT intervals in the 12-lead ECG, corrected QT and JT (QTc, JTc) using Bazett formula, and dispersion.
RESULTS. In patients with CAN time- and frequency-domain HRV were decreased in the entire 24 hours, indicating parasympathetic dysfunction: rMSSD (13.7 ± 4.28 vs. 27.12 ± 12.7 ms, p < 0.001) and high frequency (HF) power (3.67 ± 0.81 vs. 5.19 ± 0.69 lnms2, p < 0.001), as well as combined sympathetic and parasympathetic impairment: SDNN (72.41 ± 31.43 vs. 95.0 ± 27.65 ms, p < 0.05), SDNNindex (24.76 ± 9.95 vs. 48.23 ± 15.26 ms, p < 0.001), total power (Tpower) (6.23 ± 0.87 vs. 7.55 ± 0.57 lnms2,
p < 0.001) and low frequency (LF) power (4.49 ± 1.02 vs. 6.31 ± 0.57 lnms2, p < 0.001). HRV measures were also impaired at daytime and nighttime. In patients with CAN JTc on the 12-lead ECG was longer than in patients without CAN (310 ± 36 vs. 286 ± 27 ms, p < 0.05). There was a significant correlation between mean QT and very low frequency (VLF) (r = 0.50, p < 0.01), and between mean QT and LF (r = 0.35, p < 0.05). The correlation between mean QT and LF/HF ratio was of borderline significance (r = 0.32, p = 0.06). Mean QTc was correlated significantly with maximal LF/HF ratio (r = 0.39, p < 0.05). There was a correlation between mean JT and VLF (r = 0.37, p < 0.05). Mean JTc was correlated significantly with the LF/HF ratio (r = 0.34, p < 0.05), JTc dispersion was negatively correlated with minimal SDNN (r = –0.36, p < 0.05), whereas QTc dispersion with pNN50 (r = -0.34, p < 0.05).
CONCLUSIONS. Changes in time- and frequency-domain measures of HRV reflect parasympathetic dysfunction, combined sympathetic and parasympathetic impairment and impaired autonomic regulation of the heart rate. HRV parameters have been found to correlate with markers of heterogeneous ventricular repolarization. Autonomic dysfunction and impaired repolarization may provide a substrate for severe cardiac arrhythmia in patients with type 1 diabetes and CAN.
AIM OF THE STUDY. The aim of the study was to analyze time- and frequency-domain HRV in patients with type 1 diabetes and their relation with ventricular repolarization parameters: QT and JT, corrected QT and JT, and dispersion of the parameters.
MATERIAL AND METHODS. We studied 17 patients with CAN based on at least two Ewing tests and 17 patients without CAN (age: 37.76 ± 11.78 and 31.65 ± 7.98, diabetes duration 22.06 ± 10.26 and 11.94 ± 10.36 years). In all subjects we measured time- and frequency-domain components of HRV; QT and JT intervals in the 12-lead ECG, corrected QT and JT (QTc, JTc) using Bazett formula, and dispersion.
RESULTS. In patients with CAN time- and frequency-domain HRV were decreased in the entire 24 hours, indicating parasympathetic dysfunction: rMSSD (13.7 ± 4.28 vs. 27.12 ± 12.7 ms, p < 0.001) and high frequency (HF) power (3.67 ± 0.81 vs. 5.19 ± 0.69 lnms2, p < 0.001), as well as combined sympathetic and parasympathetic impairment: SDNN (72.41 ± 31.43 vs. 95.0 ± 27.65 ms, p < 0.05), SDNNindex (24.76 ± 9.95 vs. 48.23 ± 15.26 ms, p < 0.001), total power (Tpower) (6.23 ± 0.87 vs. 7.55 ± 0.57 lnms2,
p < 0.001) and low frequency (LF) power (4.49 ± 1.02 vs. 6.31 ± 0.57 lnms2, p < 0.001). HRV measures were also impaired at daytime and nighttime. In patients with CAN JTc on the 12-lead ECG was longer than in patients without CAN (310 ± 36 vs. 286 ± 27 ms, p < 0.05). There was a significant correlation between mean QT and very low frequency (VLF) (r = 0.50, p < 0.01), and between mean QT and LF (r = 0.35, p < 0.05). The correlation between mean QT and LF/HF ratio was of borderline significance (r = 0.32, p = 0.06). Mean QTc was correlated significantly with maximal LF/HF ratio (r = 0.39, p < 0.05). There was a correlation between mean JT and VLF (r = 0.37, p < 0.05). Mean JTc was correlated significantly with the LF/HF ratio (r = 0.34, p < 0.05), JTc dispersion was negatively correlated with minimal SDNN (r = –0.36, p < 0.05), whereas QTc dispersion with pNN50 (r = -0.34, p < 0.05).
CONCLUSIONS. Changes in time- and frequency-domain measures of HRV reflect parasympathetic dysfunction, combined sympathetic and parasympathetic impairment and impaired autonomic regulation of the heart rate. HRV parameters have been found to correlate with markers of heterogeneous ventricular repolarization. Autonomic dysfunction and impaired repolarization may provide a substrate for severe cardiac arrhythmia in patients with type 1 diabetes and CAN.
Keywords: diabetes mellitusheart rate variabilityventricular repolarization