1. What is Fridericia's QTc Formula?

Fridericia's formula corrects the QT interval for heart rate using a cube root correction. It provides better accuracy at heart rate extremes compared to other correction formulas like Bazett's.

2. How Does the Calculator Work?

The calculator uses Fridericia'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 accounts for the non-linear relationship between QT interval and heart rate, providing more accurate correction especially at extreme heart rates.

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 Fridericia's formula instead of Bazett's?
A: Fridericia's cube root correction provides better accuracy at heart rate extremes, while Bazett's tends to overcorrect at high heart rates and undercorrect at low heart rates.

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 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 Fridericia's formula?
A: While better than Bazett's at extremes, no single formula is perfect for all heart rates. Clinical context and multiple measurements should be considered.

Q5: Should QTc be used for medication monitoring?
A: Yes, QTc monitoring is essential for drugs that may prolong QT interval and increase risk of torsades de pointes.