1. What is the Bazett Formula?

The Bazett formula is a mathematical correction used to adjust the QT interval for heart rate, resulting in the QTc (corrected QT) value. It is one of the most commonly used formulas in clinical practice for assessing cardiac repolarization.

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 = 60 / HR (seconds)
• \( HR \) — Heart rate (beats per minute)

Explanation: The formula corrects the QT interval for heart rate, which is important because QT interval naturally varies with heart rate. However, it may over-correct at high heart rates and under-correct at low heart rates.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing cardiac repolarization abnormalities, identifying risk of arrhythmias, and monitoring drug effects that may prolong QT interval.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why correct QT interval for heart rate?
A: The QT interval naturally shortens with increasing heart rate. Correction allows comparison of QT values across different heart rates.

Q2: What are normal QTc values?
A: Normal QTc is generally <450 ms for men and <470 ms for women. Values above these may indicate prolonged QT syndrome.

Q3: When should QTc be measured?
A: QTc should be measured when assessing for arrhythmia risk, before starting medications that may prolong QT, and in patients with syncope or family history of sudden cardiac death.

Q4: Are there limitations to Bazett's formula?
A: Yes, it may over-correct at high heart rates (>100 bpm) and under-correct at low heart rates (<60 bpm). Other formulas like Fridericia may be more accurate in some cases.

Q5: Should this be used for clinical decision making?
A: While useful for screening, clinical decisions should be based on comprehensive evaluation including medical history, physical examination, and possibly multiple ECG measurements.