1. What is the Bazett Formula?

The Bazett formula is used to calculate the corrected QT interval (QTc) which accounts for variations in heart rate. It provides a standardized measure of ventricular repolarization that is independent of heart rate.

2. How Does the Calculator Work?

The calculator uses the Bazett formula:

Where:

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

Explanation: The formula corrects the QT interval for heart rate by dividing by the square root of the RR interval, providing a rate-independent measure of ventricular repolarization.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing cardiac repolarization abnormalities, identifying risk of arrhythmias, and monitoring drug effects on cardiac conduction. A QTc of 420 ms is considered the upper limit of normal.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is a normal QTc value?
A: Normal QTc values are typically <420 ms for men and <440 ms for women. Values above these thresholds may indicate prolonged QT syndrome.

Q2: Why is QTc correction important?
A: The QT interval naturally varies with heart rate. Correction allows for comparison of QT intervals at different heart rates and identification of abnormal repolarization.

Q3: When should QTc be measured?
A: QTc should be measured in standard ECG leads, preferably lead II or V5, and should be averaged over multiple beats for accuracy.

Q4: Are there limitations to the Bazett formula?
A: The Bazett formula may overcorrect at high heart rates and undercorrect at low heart rates. Other formulas (Fridericia, Framingham) may be used in specific situations.

Q5: What clinical conditions affect QTc?
A: Prolonged QTc can be caused by medications, electrolyte imbalances, congenital long QT syndrome, myocardial ischemia, and other cardiac conditions.