1. What Is QTc Correction?

QTc correction adjusts the measured QT interval for heart rate, allowing comparison across different heart rates. Various formulas exist, with Bazett's being the most commonly used.

2. How Does The Calculator Work?

The calculator uses the selected 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: Different formulas account for heart rate effects on QT interval in varying ways, with Bazett being the standard but others providing alternatives.

3. Importance Of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing risk of arrhythmias, particularly torsades de pointes, and for monitoring drug effects on cardiac repolarization.

4. Using The Calculator

Tips: Enter QT in milliseconds, HR in beats per minute, and select the desired correction formula. All values must be valid (QT > 0, HR > 0).

5. Frequently Asked Questions (FAQ)

Q1: Why use different QTc formulas?
A: Different formulas may be more accurate in specific populations or heart rate ranges. Bazett tends to overcorrect at high heart rates.

Q2: What are normal QTc values?
A: Normal QTc is typically <450 ms for men and <460 ms for women. Values >500 ms indicate high risk for arrhythmias.

Q3: When should QTc be measured?
A: QTc should be measured in patients on QT-prolonging drugs, with electrolyte abnormalities, or with symptoms suggesting arrhythmia.

Q4: Are there limitations to QTc calculation?
A: Yes, all formulas have limitations, particularly at extreme heart rates. Manual measurement of QT interval can also vary between observers.

Q5: Should QTc be used for clinical decision making?
A: QTc should be interpreted in clinical context and confirmed with repeated measurements when abnormal.