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 important because the QT interval naturally shortens with increasing heart rate. In children, a QTc value less than 440 ms is considered normal.

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 calculated as 60 / HR (seconds)
• \( HR \) — Heart rate (beats per minute)

Explanation: The formula corrects the QT interval for heart rate by dividing by the square root of the RR interval, providing a rate-independent measure of ventricular repolarization.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for detecting prolonged QT syndrome, which can increase the risk of life-threatening arrhythmias. It's particularly important in pediatric patients where normal values differ from adults.

4. Using the Calculator

Tips: Enter the measured QT interval in milliseconds and heart rate in beats per minute. Both values must be positive numbers. The calculator will automatically compute the RR interval and apply Bazett's correction.

5. Frequently Asked Questions (FAQ)

Q1: Why is QTc important in children?
A: Prolonged QTc in children can indicate congenital long QT syndrome, which increases the risk of sudden cardiac death. Early detection is crucial for management.

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 are borderline, and above 460 ms are abnormal.

Q3: Are there limitations to Bazett's formula?
A: Yes, Bazett's formula tends to overcorrect at high heart rates and undercorrect at low heart rates. Other formulas (Fridericia, Framingham) may be used in specific situations.

Q4: When should QTc be measured?
A: QTc should be measured when there's clinical suspicion of arrhythmia, family history of sudden cardiac death, or before starting medications that may prolong QT interval.

Q5: How should QT interval be measured on ECG?
A: QT interval is measured from the beginning of the QRS complex to the end of the T wave, preferably in lead II or V5 where T waves are most clearly defined.