1. What is Bazett's Formula?

Bazett's formula is the most commonly used method for correcting the QT interval for heart rate. It provides a rate-corrected QT (QTc) value that allows comparison of QT intervals 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)

Explanation: The formula corrects the QT interval for heart rate by dividing by the square root of the RR interval (in seconds).

3. Importance of QTc Calculation

Details: QTc calculation is essential for assessing cardiac repolarization and identifying potential arrhythmia risks. A QTc of 418 ms is considered normal, while prolonged QTc may indicate increased risk of torsades de pointes.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is a normal QTc value?
A: Normal QTc values are typically <450 ms for men and <470 ms for women. A value of 418 ms is within normal range.

Q2: Why is QTc correction important?
A: The QT interval naturally shortens with increasing heart rate. Correction allows comparison of QT intervals at 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, Framingham) 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 QT interval measured on ECG?
A: QT interval is measured from the beginning of the QRS complex to the end of the T wave, typically in lead II or V5.