1. What is 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)

Normal Range: 350-440 ms for men, 350-460 ms for women

3. Importance of QTc Calculation

Details: QTc measurement is crucial for assessing cardiac repolarization abnormalities. Prolonged QTc intervals may indicate increased risk of ventricular arrhythmias and sudden cardiac death.

4. Using the Calculator

Tips: Enter 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: Why is QTc correction necessary?
A: The QT interval naturally varies with heart rate. QTc correction standardizes the measurement to a heart rate of 60 bpm for meaningful comparison.

Q2: What are the clinical implications of prolonged QTc?
A: QTc > 440-460 ms (depending on gender) may indicate increased risk of torsades de pointes and other ventricular arrhythmias.

Q3: Are there limitations to Bazett's formula?
A: Bazett's formula may overcorrect at high heart rates and undercorrect at 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 affect cardiac repolarization, those with electrolyte imbalances, or with personal/family history of arrhythmias.

Q5: How is the QT interval measured on ECG?
A: The QT interval is measured from the beginning of the QRS complex to the end of the T wave, typically in lead II or V5 where the T wave is most clearly defined.