Clinical significance of heart rate variability and Q-T interval duration during Holter monitoring of ECG in patients with essential hypertension

The clinical significance of heart rate variability and Q-T interval duration during 24-hour bifunctional monitoring of ECG and blood pressure (BP) was studied in 81 patients aged 22-58 years (mean 41,40±0,72 years) who had Stages I-III essential hypertension (EH). A comparison group included 20 healthy individuals. Temporary and spectral methods were used to assess the parameters of heart rate variability; 24-hour Q-Tand O-Tk intervals, as well as echocardiographic data were analyzed. Patients with Stages I-III EH were ascertained to have a progressive decrease in diurnal heart rate variability along with a reduction in the total power of the spectrum, in the power of low-frequency constituents, and in their ratio. EH progression was found to be associated with an increase in the duration of the Q-T interval, its corrected values during daylight hours and with the degree of heart rate variability without circadian changes. The degree of autonomous cardiac control was statistically significantly related to heart rate variability and a risk for ventricular repolarization disorders.