QTIntervall
QTintervall, denoted as the QT interval in English, is the portion of the electrocardiogram (ECG) from the onset of the Q wave to the end of the T wave. It represents the total time for ventricular depolarization and repolarization. The QT interval shortens and lengthens with heart rate, so a heart-rate–corrected value, QTc, is commonly used to compare intervals across different rates. Common correction methods include Bazett’s formula (QTc = QT / sqrt(RR)) and Fridericia’s (QTc = QT / RR^(1/3)); several other formulas exist, each with limitations.
Normal QT and QTc values depend on sex and age. Typical upper limits are around 440 ms
Prolonged QT can be congenital (long QT syndromes) or acquired. Congenital forms arise from mutations in cardiac
Measurement should be performed on a stable rhythm, with careful identification of the Q wave onset and