1. What is QTc Calculation?

QTc (Corrected QT interval) calculation adjusts the measured QT interval for heart rate using Bazett's formula. This is particularly important in pediatric patients to assess cardiac repolarization and identify potential arrhythmia risks.

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: The formula corrects the QT interval for heart rate variations, providing a standardized measure of ventricular repolarization.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for detecting prolonged QT syndrome, assessing arrhythmia risk, and monitoring medication effects on cardiac repolarization in pediatric patients.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and heart rate in beats per minute. Normal QTc is typically <440 ms in children. Values ≥440 ms may indicate abnormal cardiac repolarization.

5. Frequently Asked Questions (FAQ)

Q1: Why use Bazett's formula for children?
A: Bazett's formula is widely accepted and validated for pediatric QTc correction, though it may overcorrect at extreme heart rates.

Q2: What are normal QTc values in children?
A: Normal QTc is generally <440 ms. Values between 440-460 ms are borderline, and >460 ms are considered prolonged in most pediatric guidelines.

Q3: When should QTc be measured?
A: QTc should be measured during routine ECG screening, before starting medications that affect QT interval, and in patients with syncope or family history of sudden cardiac death.

Q4: Are there limitations to Bazett's formula?
A: Yes, it tends to overcorrect at high heart rates and undercorrect at low heart rates. Alternative formulas (Fridericia, Hodges) may be used in specific situations.

Q5: What factors can affect QTc measurement?
A: Electrolyte imbalances, medications, autonomic nervous system activity, and measurement technique can all affect QTc values.