1. What Is The QTc Calculation?

The QTc (Corrected QT Interval) calculation adjusts the measured QT interval for heart rate using Bazett's formula. This provides a standardized measure of ventricular repolarization that can be compared across different heart rates.

2. How Does The Calculator Work?

The calculator uses Bazett's formula:

Where:

• \( QT \) — Measured QT interval from start of Q wave to end of T wave (ms)
• \( RR \) — RR interval = 60 / HR (seconds)
• \( HR \) — Heart rate (beats per minute)

Example: QT = 420 ms, RR = 0.9 s (HR = 67 bpm), QTc = 443 ms

3. Importance Of QTc Calculation

Details: QTc calculation is essential for assessing cardiac repolarization abnormalities. Prolonged QTc intervals are associated with increased risk of life-threatening arrhythmias, particularly torsades de pointes.

4. Using The Calculator

Tips: Enter the measured QT interval in milliseconds and heart rate in beats per minute. Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal QTc value?
A: Normal QTc values are typically <440 ms for men and <460 ms for women. Values above these thresholds may indicate prolonged QT syndrome.

Q2: Why is QTc correction important?
A: The QT interval naturally shortens with faster heart rates. QTc correction allows comparison of QT intervals across different heart rates.

Q3: Are there limitations to Bazett's formula?
A: Bazett's formula may overcorrect at very high heart rates and undercorrect at very low heart rates. Other formulas (Fridericia, Framingham) may be used in specific situations.

Q4: When should QTc be measured?
A: QTc should be measured in patients taking medications that may prolong QT interval, in those with syncope or family history of sudden cardiac death, and in routine cardiac assessments.

Q5: How is QTc measurement performed clinically?
A: QTc is typically measured from a 12-lead ECG, averaging measurements from multiple leads for accuracy, preferably lead II or V5.