Prolongation of the QT interval

In recent years in clinical cardiology, the problem of prolonging the QT interval has attracted close attention of domestic and foreign researchers as a factor leading to sudden death. It has been established that both congenital and acquired forms of QT interval prolongation are predictors of fatal rhythm disturbances, which, in turn, lead to sudden death of patients.

The QT prolongation syndrome is a combination of an extended QT interval of the standard ECG and life-threatening polymorphic ventricular tachycardia (torsade de pointes). Paroxysms of ventricular tachycardias such as pirouettes are clinically manifested in the form of episodes of loss of consciousness and often end with fibrillation of the ventricles, which are dopartic to sudden death.

The duration of the QT interval depends on the heart rate and the patient's sex. Therefore, use is not absolute, but the corrected QT interval (QTc), which depends on the heart rate, and also on the pacemaker.

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The classification of the long QT syndrome is based on an analysis of the molecular-genetic and clinical features of the disease and currently includes 15 molecular-genetic variants.

Several variants of the syndrome are phenotypically distinguished: the most common Romano-Ward syndrome, less common, but more malignant Jervell-Lange-Nielsen syndrome, and Timothy syndrome, as well as the Andersen-Tavil syndrome.

Syncopal states can manifest at any age. Prognostically unfavorable is the age of the first syncope manifestation earlier than 6 years. The risk of developing life-threatening events, such as syncope, sudden stop of blood circulation and sudden cardiac death, depends to a large extent on age and sex. In the vast majority of cases, syncopal conditions develop against a background of stressful situations (physical activity, emotional arousal).

Molecular-genetic analysis is recommended to verify the diagnosis, determine the prognosis of the disease.

Therapy of patients with long QT syndrome includes lifestyle adjustments; drug and non-drug prophylaxis of sudden cardiac death, as well as emergency therapy of ventricular tachycardia.

First of all, all patients are recommended to exclude the use of drugs that extend the QT interval. Occupations of professional sports are contraindicated in patients with syncopal form of long QT syndrome and patients from the high-risk group. In the absence of clinical manifestations and genetically confirmed by long QT syndrome, the decision is made by the medical commission on an individual basis. The most effective method of preventing sudden cardiac death is implantation of a cardioverter-defibrillator, which is mandatory for all patients who underwent a sudden stop of blood circulation, and also in the presence of spontaneous stable ventricular tachycardia with or without syncope.