QTc interval
Pronunciation: Q-T-C interval
Also written as: QTc — corrected QT interval
Heart rate-corrected QT interval on ECG, representing ventricular depolarization and repolarization time.
Full Definition
The QTc interval is the QT interval corrected for heart rate, typically calculated using Bazett's formula (QT/√RR). It represents the duration of ventricular electrical activity from the beginning of ventricular depolarization to the end of repolarization. Normal QTc values are generally less than 440 ms in men and 460 ms in women. QTc prolongation can predispose patients to torsades de pointes, a potentially fatal ventricular arrhythmia. Many medications can prolong the QTc interval, making monitoring essential in clinical practice, particularly when prescribing antiarrhythmic drugs, antibiotics, or psychiatric medications.
Usage
Usage note: Always specify the correction formula used; Bazett's formula is most common but may overcorrect at high heart rates.
In Context
- "The patient's QTc interval was prolonged at 485 ms, prompting discontinuation of the antiarrhythmic medication." — ECG interpretation
- "Serial ECGs were ordered to monitor QTc interval changes during amiodarone therapy." — medication monitoring protocol