1. What is QTc Calculation?

The QTc (Corrected QT Interval) calculation adjusts the measured QT interval for heart rate using Bazett's formula. This correction is essential for accurate assessment of cardiac repolarization and detection of potential arrhythmia risks.

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, providing a standardized measure of ventricular repolarization.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing risk of torsades de pointes, monitoring drug effects on cardiac repolarization, and evaluating patients with congenital long QT syndrome.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and heart rate in beats per minute. Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal QTc value?
A: Normal QTc values are typically <440 ms for men and <460 ms for women. Values above these thresholds 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 cardiac repolarization, those with electrolyte imbalances, or when evaluating syncope and 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 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 for consistency.