1. What is Bazett's Formula?

Bazett's formula is used to calculate the corrected QT interval (QTc) from the measured QT interval and heart rate. It accounts for the fact that the QT interval normally shortens with increasing heart rate.

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 corrects the QT interval for heart rate by dividing by the square root of the RR interval.

3. Importance of QTc Calculation

Details: QTc calculation is crucial for assessing cardiac repolarization and detecting prolonged QT intervals, which can indicate increased risk of life-threatening arrhythmias.

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: 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 is QTc important?
A: Prolonged QTc intervals are associated with increased risk of torsades de pointes, a potentially fatal ventricular arrhythmia.

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 like Fridericia's may be used in certain situations.

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

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.