1. What is the QTc Interval?

The QTc (Corrected QT) interval represents the QT interval adjusted for heart rate using Bazett's formula. It provides a standardized measure of ventricular repolarization that accounts for variations in heart rate.

2. How Does the Calculator Work?

The calculator uses Bazett's formula:

Where:

• \( QT \) — Measured QT interval 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 variations, providing a standardized 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 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 <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 due to its simplicity and clinical validation, though it may overcorrect at high heart rates.

Q3: When should QTc be measured?
A: QTc should be measured in patients taking medications that affect cardiac repolarization, those with syncope, or when assessing risk of arrhythmias.

Q4: Are there limitations to Bazett's formula?
A: The formula may overcorrect at high heart rates (>100 bpm) and undercorrect at low heart rates (<60 bpm). Alternative formulas exist for extreme rates.

Q5: How is QT interval measured on ECG?
A: QT interval is measured from the beginning of the QRS complex to the end of the T wave, typically in lead II or V5 for consistency.