1. What is the Corrected QTc Interval?

The corrected QTc interval is a heart rate-adjusted QT interval that helps identify abnormal cardiac repolarization. It's commonly calculated using Bazett's formula to account for variations in heart rate.

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 (s)
• \( HR \) — Heart rate (bpm)

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

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for detecting long QT syndrome, assessing arrhythmia risk, and monitoring drug effects on cardiac repolarization.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and heart rate in beats per minute. All values must be valid (QT > 0, HR > 0).

5. Frequently Asked Questions (FAQ)

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

Q2: Why use Bazett's formula?
A: Bazett's formula is the most widely used method for QT correction, though it may overcorrect at high heart rates and undercorrect at low heart rates.

Q3: When should QTc be measured?
A: QTc should be measured in standard ECG leads, preferably lead II or V5, and averaged over multiple beats for accuracy.

Q4: Are there alternative correction formulas?
A: Yes, other formulas include Fridericia's (QTc = QT/RR^1/3) and Framingham's (QTc = QT + 0.154*(1-RR)) corrections.

Q5: What clinical conditions affect QTc?
A: Many medications, electrolyte imbalances, and cardiac conditions can prolong QTc and increase risk of torsades de pointes.