1. What is QTc?

QTc (Corrected QT Interval) is a heart rate-corrected measurement of the QT interval from an electrocardiogram (ECG). It accounts for variations in heart rate to provide a standardized measure of ventricular repolarization.

2. How Does the Calculator Work?

The calculator uses Bazett's formula:

Where:

• \( QT \) — QT interval measured from start of Q wave to end of T wave (ms)
• \( RR \) — RR interval = 60 / HR (seconds)
• \( HR \) — Heart rate (beats per minute)

Note: For children, normal QTc is generally considered to be less than 440 ms.

3. Importance of QTc Calculation

Details: QTc measurement is crucial for detecting prolonged QT syndrome, which can increase the risk of life-threatening arrhythmias. It's particularly important in pediatric cardiology to identify congenital or acquired long QT syndromes.

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 compute the heart rate-corrected QT interval.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal QTc value for children?
A: For children, normal QTc is generally considered to be less than 440 milliseconds. Values above this may indicate prolonged QT syndrome.

Q2: Why is QTc correction important?
A: The QT interval naturally shortens with faster heart rates and lengthens with slower rates. QTc correction allows for comparison of QT intervals across different heart rates.

Q3: When should QTc be measured?
A: QTc should be measured during routine ECG examinations, especially if there's family history of sudden cardiac death, syncope, or when certain medications are prescribed.

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

Q5: What factors can affect QTc measurement?
A: Electrolyte imbalances, certain medications, congenital syndromes, and myocardial ischemia can all affect QTc duration.