1. What is the Mayo Clinic QT Calculator?

The Mayo Clinic QT Calculator uses Bazett's formula to calculate the corrected QT interval (QTc), adjusted for rhythm, gender, and age-specific normals. It provides a standardized measurement of ventricular repolarization.

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

Explanation: The formula corrects the measured QT interval for heart rate, providing a standardized QTc value that accounts for variations in cardiac cycle length.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing cardiac repolarization abnormalities, identifying risk of arrhythmias, and monitoring drug effects on cardiac conduction.

4. Using the Calculator

Tips: Enter QT interval in milliseconds, heart rate in beats per minute, select gender and enter age. All values must be valid (QT > 0, HR > 0, age between 1-120).

5. Frequently Asked Questions (FAQ)

Q1: Why use Bazett's formula for QTc calculation?
A: Bazett's formula is the most widely used and clinically validated method for heart rate correction of the QT interval.

Q2: What are normal QTc values?
A: Normal QTc is generally <440 ms for men and <460 ms for women. Values above these may indicate prolonged QT syndrome.

Q3: When should QT measurement be performed?
A: QT measurement should be done on resting ECGs, avoiding periods of tachycardia or bradycardia that may affect accuracy.

Q4: Are there limitations to Bazett's formula?
A: The formula may overcorrect at high heart rates and undercorrect at low heart rates. Other formulas (Fridericia, Framingham) may be used in specific situations.

Q5: Why are gender and age adjustments important?
A: Women typically have longer QTc intervals than men, and QTc may vary with age. These adjustments provide more accurate reference ranges.