1. What Does QTc Calculation Mean?

The QTc (corrected QT interval) is the heart rate-corrected QT interval, assessing ventricular repolarization. It helps identify abnormal cardiac repolarization that may predispose to arrhythmias.

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

Explanation: The formula corrects the measured QT interval for heart rate, as QT interval naturally shortens with increasing heart rate.

3. Importance of QTc Calculation

Details: QTc calculation is essential for detecting prolonged QT syndrome, assessing drug-induced QT prolongation, and evaluating cardiac repolarization abnormalities that may lead to life-threatening arrhythmias.

4. Using the Calculator

Tips: Enter 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?
A: Normal QTc values are typically <440 ms for men and <460 ms for women. Values above these thresholds may indicate prolonged QT syndrome.

Q2: Why is QTc correction important?
A: QT interval varies with heart rate. Correction allows comparison of QT values across different heart rates and identification of true repolarization abnormalities.

Q3: What are the clinical implications of prolonged QTc?
A: Prolonged QTc increases risk of torsades de pointes, a potentially fatal ventricular arrhythmia. It requires careful monitoring and possible intervention.

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: When should QTc be measured?
A: QTc should be measured in patients taking QT-prolonging medications, with family history of sudden cardiac death, or with symptoms suggesting arrhythmias.