Covid QT Calculator

Fridericia Formula:

\[ QTc = \frac{QT}{\sqrt[3]{RR}} \]

Corrected QT Interval (QTc):

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1. What is the Fridericia Formula?

The Fridericia formula is used to calculate the corrected QT interval (QTc) by accounting for heart rate variations. It is particularly important in COVID monitoring as certain treatments may affect cardiac repolarization.

2. How Does the Calculator Work?

The calculator uses the Fridericia formula:

\[ QTc = \frac{QT}{\sqrt[3]{RR}} \]

Where:

\( QT \) — Measured QT interval 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 QT interval for heart rate using a cube root correction, providing a more accurate assessment of ventricular repolarization.

3. Importance of QTc Calculation in COVID Monitoring

Details: Accurate QTc monitoring is crucial during COVID treatment as certain medications used (such as hydroxychloroquine, azithromycin) can prolong QT interval and increase risk of torsades de pointes.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and heart rate in beats per minute. Both values must be valid (QT > 0, HR > 0).

5. Frequently Asked Questions (FAQ)

Q1: Why use Fridericia formula for QT correction?
A: Fridericia formula provides a more accurate correction than Bazett's formula, especially at extreme heart rates, making it suitable for COVID monitoring.

Q2: What are normal QTc values?
A: Normal QTc is typically <440 ms for men and <460 ms for women. Values >500 ms indicate high risk for arrhythmias.

Q3: When should QTc be monitored during COVID treatment?
A: QTc should be monitored before starting treatment, during treatment, and after completion, especially when using QT-prolonging medications.

Q4: Are there limitations to Fridericia formula?
A: While more accurate than Bazett's, all QT correction formulas have limitations in certain populations and should be interpreted in clinical context.

Q5: What actions should be taken if QTc is prolonged?
A: If QTc exceeds 500 ms or increases by >60 ms from baseline, consider dose reduction, alternative therapy, or closer monitoring.