QTc Interval Calculator

QTc is the heart rate-corrected QT interval on an electrocardiogram (ECG). The QT interval represents the time for ventricular depolarization and repolarization. Since the QT interval shortens with increasing heart rate, correction formulas normalize it to a rate of 60 bpm for proper comparison.

Bazett is the most commonly used and widely recognized formula, but it overestimates QTc at higher heart rates. Fridericia is considered more accurate across a wider range of heart rates and is preferred by the FDA for drug safety studies. Framingham and Hodges are linear corrections that avoid the over-correction issue.

Prolonged QT can be congenital (Long QT Syndrome types 1-17) or acquired. Common acquired causes include medications (antiarrhythmics, antibiotics like azithromycin/fluoroquinolones, antipsychotics, methadone), electrolyte abnormalities (hypokalemia, hypomagnesemia, hypocalcemia), bradycardia, and structural heart disease.

Torsades de Pointes (TdP) is a life-threatening polymorphic ventricular tachycardia associated with prolonged QT intervals. It can degenerate into ventricular fibrillation and cause sudden cardiac death. Treatment includes IV magnesium, overdrive pacing, and stopping offending medications.