1. What is QTc Calculation?

The QTc (corrected QT interval) calculation adjusts the measured QT interval for heart rate using Bazett's formula. This is particularly important in infants and children, where normal QTc should be less than 440 ms.

2. How Does the Calculator Work?

The calculator uses Bazett's formula:

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: This formula corrects the QT interval for heart rate variations, providing a standardized measure that can be compared across different heart rates.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for detecting prolonged QT intervals, which may indicate increased risk of life-threatening arrhythmias such as torsades de pointes, especially in pediatric populations.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and heart rate in beats per minute. Both values must be positive numbers. Normal QTc in children is typically less than 440 ms.

5. Frequently Asked Questions (FAQ)

Q1: Why use Bazett's formula for children?
A: Bazett's formula is recommended for infants and children as it has been extensively validated in pediatric populations and accounts for the physiological variations in heart rate common in this age group.

Q2: What is considered a normal QTc in children?
A: A QTc less than 440 ms is generally considered normal in children. Values between 440-460 ms may indicate borderline prolongation, while values above 460 ms are considered abnormal.

Q3: When should QTc be measured?
A: QTc should be measured in standard ECG recordings, preferably in lead II or V5 where the T wave is most clearly defined. Multiple measurements should be averaged for accuracy.

Q4: Are there limitations to Bazett's formula?
A: Bazett's formula may overcorrect at very high heart rates and undercorrect at very low heart rates. Alternative formulas (Fridericia, Hodges) may be considered in extreme cases.

Q5: What conditions can cause prolonged QTc?
A: Prolonged QTc can be caused by congenital long QT syndrome, electrolyte imbalances, certain medications, myocardial ischemia, and various neurological disorders.