1. What is QTc Calculation?

The QTc (Corrected QT Interval) calculation adjusts the measured QT interval for heart rate using the RR interval. It provides a standardized measure of ventricular repolarization that accounts for variations in heart rate.

2. How Does the Calculator Work?

The calculator uses the Bazett's formula:

Where:

• \( QT \) — QT interval measured from start of Q wave to end of T wave (ms)
• \( RR \) — RR interval in seconds (s)

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 assessing cardiac repolarization abnormalities, identifying risk of arrhythmias, and monitoring drug effects on cardiac conduction.

4. Using the Calculator

Tips: Enter QT interval in milliseconds (ms) and RR interval in seconds (s). Both values must be positive numbers. The RR interval can be calculated as 60/HR where HR is heart rate in beats per minute.

5. Frequently Asked Questions (FAQ)

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

Q2: Why use RR interval instead of heart rate?
A: The RR interval (in seconds) is the direct measurement needed for the square root calculation in Bazett's formula, providing more precise correction.

Q3: How do I measure QT and RR intervals?
A: QT is measured from the start of the Q wave to the end of the T wave on ECG. RR is the interval between two consecutive R waves.

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 monitored?
A: QTc should be monitored when prescribing medications that affect cardiac repolarization, in patients with cardiac conditions, or when evaluating syncope and arrhythmias.