1. What is the Mayo QTc Correction?

The Mayo QTc Correction uses Bazett's formula to adjust the QT interval for heart rate, providing a standardized measure (QTc) that accounts for variations in cardiac cycle length.

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 (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, providing a rate-independent measure of ventricular repolarization.

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

5. Frequently Asked Questions (FAQ)

Q1: Why use Bazett's formula for QTc correction?
A: Bazett's formula is widely used and clinically validated for heart rate correction of QT interval, though it may overcorrect at extreme heart rates.

Q2: What are normal QTc values?
A: Normal QTc is generally <450 ms for men and <460 ms for women. Prolonged QTc increases risk of torsades de pointes.

Q3: 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.

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

Q5: Should QTc monitoring be done for drug therapy?
A: Yes, many drugs (especially antiarrhythmics and psychotropics) require regular QTc monitoring to assess risk of arrhythmogenicity.