1. What is the Fridericia QTc Formula?

The Fridericia formula is one of several methods used to correct the QT interval for heart rate. It provides a rate-corrected QT interval (QTc) that allows for comparison of QT values across different heart rates.

2. How Does the Calculator Work?

The calculator uses the Fridericia formula:

Where:

• \( QT \) — Measured QT interval from start of Q wave to end of T wave (ms)
• \( RR \) — RR interval calculated as \( RR = \frac{60}{HR} \) (s)
• \( HR \) — Heart rate (bpm)

Explanation: The formula corrects the measured QT interval for heart rate using a cube root correction, providing a standardized QTc value.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing cardiac repolarization, 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, and select gender. All values must be valid (QT > 0, HR > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the normal range for QTc?
A: Normal range is 350-440 ms for adults; prolonged if >440 ms for men, >460 ms for women.

Q2: Why use Fridericia instead of Bazett?
A: Fridericia formula is generally more accurate at extreme heart rates and less likely to overcorrect compared to Bazett formula.

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: What causes prolonged QTc?
A: Prolonged QTc can be caused by medications, electrolyte imbalances, congenital syndromes, or myocardial ischemia.

Q5: Is short QTc concerning?
A: Short QTc (<350 ms) may be associated with increased risk of arrhythmias and should be evaluated clinically.