Title: Abnormal QT interval syndromes
- Marlena Olszak, Gabriela Parol-Baran, Mirosław Dziuk, Tomasz Słelmaszuk
- Review articles
- Polish Journal of Cardiology
- Start page:
- Final page:
- long and short QT interval, ion channels, arrhythmia, sudden cardiac death
Malignant ventricular heart ratę abnormalities frequently cause sudden cardiac death. Understading the me-chanisms underlying of life-threatening arrhythmias allows to evaluate the risk of sudden cardiac death and to undertake the adequate treatment early on. The QT interval measurement on an ECG print-out is an ea-sy and noninvasive way allowing for an identification of patients threatened by malignant ventricular arrhythmias. The QT interval has been mainly attributed to ventricular repolarization. Proper repolarization requires the balance between the inward ionic celi currents (sodium and calcium) and outward potassium celi cur-rents. Any causes, either inherited or acquired, that impede a proper functioning of ionic channels through their intensified activation or inactivation, result in the prolongation or shortening of the QT interval, increa-sed risk of life-threatening ventricular arrhythmias and sudden cardiac death. The prolongation of the corrected QT interval (QTc) is an independent risk factor for SCD (1, 2). In subjects who do not suffer from an organie cardiac pathology the QTc interval above 440 ms is related to a two- or threefold greater risk of sudden cardiac death (3). Correlations between the prolonged QT interval and the sudden cardiac death are considered valid but on the other hand there exists Iittie information concerning the prognostic significan-ce of short QT interval. It seems that the shortening of QT interval under the value of 300 ms may also be related to an inereased risk of sudden cardiac death (4).