1. What Is QTc Calculation?

QTc calculation corrects the QT interval for heart rate, allowing for standardized assessment of cardiac repolarization across different heart rates. MDCalc uses Bazett's formula by default but also supports Fridericia, Framingham, and Hodges formulas for QT correction.

2. How Does The Calculator Work?

The calculator uses different formulas based on selection:

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)

3. Importance Of QTc Calculation

Details: QTc is crucial for assessing risk of arrhythmias, particularly torsades de pointes. Prolonged QTc may indicate increased risk and requires clinical evaluation.

4. Using The Calculator

Tips: Enter QT interval in milliseconds, heart rate in beats per minute, and select the desired correction formula. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why are there different QT correction formulas?
A: Different formulas have varying accuracy across heart rate ranges. Bazett tends to overcorrect at high heart rates, while other formulas may provide better correction in specific scenarios.

Q2: What is a normal QTc value?
A: Normal QTc is typically <450 ms for men and <470 ms for women. Values above these may indicate prolonged QT interval.

Q3: When should QTc be measured?
A: QTc should be measured in patients taking medications that may prolong QT interval, or when assessing risk of arrhythmias.

Q4: Are there limitations to QT correction?
A: Yes, all formulas have limitations, especially at extreme heart rates. Clinical judgment should always accompany automated calculations.

Q5: Which formula is most accurate?
A: No single formula is perfect for all situations. Bazett is most commonly used, but Fridericia or Hodges may be preferred in specific clinical contexts.