1. What is Bazett's Correction Formula?

Bazett's formula is used to correct the QT interval for heart rate, providing a rate-independent measure of ventricular repolarization. It is commonly used in clinical practice to assess the risk of arrhythmias.

2. How Does the Calculator Work?

The calculator uses Bazett's formula:

Where:

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

Explanation: The formula adjusts the QT interval based on the square root of the RR interval to account for heart rate variations.

3. Importance of QTc Calculation

Details: Corrected QT interval is crucial for identifying prolonged QT syndrome, assessing arrhythmia risk, and monitoring drug effects on cardiac repolarization.

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 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 interval 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 standard ECG leads, preferably lead II or V5, and averaged over multiple beats for accuracy.

Q5: What clinical conditions affect QTc?
A: Various conditions including electrolyte imbalances, medications, congenital syndromes, and myocardial ischemia can prolong QTc interval.