[Characteristics of 24-hour ECG and the regulation of cardiac rhythm in adolescents]. / Kharakteristika sutochnoi EKG i reguliatsii serdechnogo ritma u podrostkov.

Holter 24-hour monitoring was performed in 50 healthy subjects aged 11-15 years. Daily changes and standard values of heart rate (HR), P-R and Q-T intervals, P, R, T wave amplitudes, ST segment displacement were determined. All the patients under study exhibited sinus arrhythmia, pacemaker migration periods, short cardiac rhythm pauses (up to 1.5 s). Three adolescents were recorded to have Degree I atrioventricular block at night, 3 presented with rare (up to 2 per min) supraventricular contraction beats, 1 had a nocturnal transient Wolff-Parkinson-White syndrome. Despite HR at night, there were periods of Q-T interval prolongation. Daily changes in the neurohumoral regulation of the heart and its relation to the occurrence of various electrocardiographic events were determined.