1. What is QTc Calculation?

The QTc (Corrected QT Interval) calculation adjusts the measured QT interval for heart rate using Bazett's formula. This provides a standardized measure of ventricular repolarization that can be compared across different heart rates.

2. How Does the Calculator Work?

The calculator uses Bazett's formula:

Where:

• \( QT \) — QT interval in milliseconds (each little box = 40 ms)
• \( RR \) — RR interval in seconds (calculated as 60/HR)
• \( HR \) — Heart rate in beats per minute (bpm)

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

3. Importance of QTc Calculation

Details: QTc calculation is essential for assessing cardiac repolarization abnormalities. Prolonged QTc intervals may indicate increased risk of life-threatening arrhythmias, particularly torsades de pointes.

4. Using the Calculator

Tips: Count the number of little boxes for the QT interval (each box = 40 ms), enter the heart rate in bpm. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal QTc value?
A: Normal QTc is typically <440 ms for men and <460 ms for women. Values above these may indicate prolonged QT syndrome.

Q2: Why use little boxes for measurement?
A: Standard ECG paper has small boxes representing 40 ms and large boxes representing 200 ms, making visual measurement convenient.

Q3: What are the limitations of 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.

Q4: When should QTc be measured?
A: QTc should be measured in leads where the T wave is clearly defined, typically lead II or V5. The longest QT interval across leads should be used.

Q5: What factors can affect QTc?
A: Medications, electrolyte imbalances, genetic factors, and various medical conditions can prolong QTc interval.