Corrected QT Interval

The Corrected QT Interval (QTc) adjusts the measured QT interval for heart rate, allowing comparison across different heart rates. A prolonged QTc indicates delayed ventricular repolarization and increased risk of ventricular arrhythmias, particularly torsades de pointes.

• Normal QTc: ≤430 ms (men), ≤450 ms (women)
• QTc >500 ms = HIGH risk of torsades de pointes
• RR interval (seconds) = 60 / heart rate
• Common QT-prolonging drugs: haloperidol, methadone, fluoroquinolones, azithromycin, ondansetron, amiodarone
• Always check K⁺ and Mg²⁺ in patients with prolonged QT

• Drug monitoring: Many drugs prolong QT (antipsychotics, antibiotics, antiarrhythmics)
• Risk stratification: Prolonged QTc increases risk of sudden cardiac death
• Congenital Long QT Syndrome: Diagnosis and management
• Electrolyte monitoring: Hypokalemia, hypomagnesemia, hypocalcemia prolong QT