1. What is QTc Interval?

The QTc interval is the heart rate-corrected QT interval measured from the start of the Q wave to the end of the T wave in the heart's electrical cycle. It provides a standardized measure of ventricular repolarization that accounts for variations in heart rate.

2. How Does the Calculator Work?

The calculator uses the 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 measured 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 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. Both values must be valid positive numbers.

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 is QTc correction important?
A: The QT interval naturally shortens with faster heart rates. QTc correction allows comparison of QT intervals across different heart rates.

Q3: When should QTc be measured?
A: QTc should be measured when evaluating patients for arrhythmia risk, before starting medications that affect QT interval, and in patients with syncope or family history of sudden cardiac death.

Q4: Are there limitations to Bazett's formula?
A: Bazett's formula may overcorrect at very high heart rates and undercorrect at very low heart rates. Other formulas like Fridericia's may be used in specific situations.

Q5: What factors can affect QTc interval?
A: Medications, electrolyte imbalances, cardiac conditions, and genetic factors can all affect QTc interval duration.