1. What is the QTc Calculation?

The QTc (Corrected QT Interval) calculation using Bazett's formula adjusts the measured QT interval for heart rate, providing 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 (s)
• \( HR \) — Heart rate (bpm)

Explanation: The formula corrects the QT interval for heart rate by dividing by the square root of the RR interval, providing a heart rate-independent measure of ventricular repolarization.

3. Importance of QTc Calculation

Details: Accurate QTc measurement is crucial for assessing risk of arrhythmias, monitoring drug effects (especially those that prolong QT interval), 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. The calculator will compute the RR interval and apply Bazett's correction.

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 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 known to prolong QT interval, those with syncope or palpitations, 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 (Fridericia, Framingham) 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.