1. What is Bazett's Formula?

Bazett's formula is used to correct the QT interval for heart rate, providing the QTc (corrected QT) value. This correction is essential for accurate assessment of cardiac repolarization 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 (s)
• \( HR \) — Heart rate (bpm)

Explanation: The formula adjusts the QT interval based on the square root of the RR interval, accounting for the inverse relationship between heart rate and QT duration.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for detecting prolonged QT intervals, which may indicate increased risk of life-threatening arrhythmias such as Torsades de Pointes.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and heart rate in beats per minute. Both values must be valid (QT > 0, HR > 0).

5. Frequently Asked Questions (FAQ)

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

Q2: Why correct QT for heart rate?
A: The QT interval naturally shortens with increasing heart rate. Correction allows comparison of QT values across different heart rates.

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, Hodges) may be used in specific situations.

Q4: When should QTc be measured?
A: QTc should be measured in patients taking medications that prolong QT interval, or when evaluating for congenital long QT syndrome.

Q5: How is the RR interval calculated?
A: RR interval (in seconds) = 60 / heart rate (in beats per minute).