Holter monitoring in the long QT syndrome of children and adolescents.

Results of Holter monitoring (HM) of ECG in 45 patients with long QT syndrome (LOTS) and 26 healthy control children are presented. 15 patients had a history of syncopal attacks (group I), other patients were symptomless (group II). Heart rate-corrected QT interval (QTc) on standard resting ECG exceeded 460 ms in 73.3% of patients in group I and in 44.8% of group II patients. On Holter monitoring, it was present in 100% of group I and 83.9% of group II patients. T wave alternation was registered in 66.6% of group I and 56.7% of group II patients. Ventricular arrhythmia was not found on standard resting ECG in any of the examined children, whereas Holter monitoring revealed ventricular extrasystoles in 53.3% of group I and 6.7% of group II patients (p less than 0.05). In one case early ventricular extrasystoles accompanied an attack of ventricular tachycardia. Mathematical analysis of 24-h extracardial heart rhythm regulation revealed its disturbance in LQTS patients compared to healthy children, as well as asthenic signs in the sympathetic nervous system. These changes were more pronounced in patients with a more severe course of the disease (group I).

[Ultrastructure of the sinoatrial area of the heart during the long Q-T syndrome]. / Ul'trastruktura sinoaurikuliarnoi oblasti serdtsa pri sindrome udlinennogo intervala Q-T.

The conducting myocardia of the sinus node and prenodal working ones of the right atrium, which had been dissected from 6 patients aged 10-40 years with the prolonged Q-T interval syndrome during an operation on implantation of an artificial pacemaker were examined. Acute and chronic destructive changes were found in the conducting and working myocytes of the sinoauricular region in the heart. Some cases displayed abnormal contact interrelationships of myocytes. Destructive changes were observed in non-myelinated and myelinated nerve fibers, microcirculatory bed, and the connective tissue component of the conducting and working myocardium. The abnormalities found in the cardiac sinoauricular region are discussed to be a possible substrate for the development of life-threatening arrhythmias in patients with the prolonged Q-T interval syndrome.