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:

• \( QT \) — Measured QT interval from start of Q wave to end of T wave (ms)
• \( RR \) — RR interval = 60 / HR (seconds)
• \( HR \) — Heart rate (beats per minute)

Explanation: The formula corrects the QT interval for heart rate variations, allowing for standardized assessment of cardiac repolarization across different heart rates.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing risk of arrhythmias, monitoring drug effects on cardiac repolarization, and evaluating patients with potential Long QT Syndrome.

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 <450 ms for men and <460 ms for women. Values above these may indicate prolonged QT interval.

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

Q3: When should QTc be measured?
A: QTc should be measured in patients taking medications that affect QT interval, those with syncope or arrhythmias, and in screening for congenital Long QT Syndrome.

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 may be used in these cases.

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