1. What is Corrected QT Interval?

The Corrected QT Interval (QTc) is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle, adjusted for heart rate. It helps in assessing the risk of ventricular arrhythmias.

2. How Does the Calculator Work?

The calculator uses the Bazett formula:

Where:

• \( QT \) — QT interval measured from start of Q wave to end of T wave (ms)
• \( RR \) — RR interval = 60 / HR (s)
• \( HR \) — Heart rate (bpm)

Explanation: The formula adjusts the QT interval for heart rate to provide a standardized measure that can be compared across different heart rates.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for diagnosing long QT syndrome, assessing arrhythmia risk, and monitoring effects of medications that may prolong QT interval.

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: Why correct QT interval for heart rate?
A: The QT interval naturally shortens with increasing heart rate. Correction allows comparison of QT values at different heart rates.

Q2: What are normal QTc values?
A: Normal QTc is typically <440 ms for men and <460 ms for women. Values above these may indicate prolonged QT interval.

Q3: When should QTc be measured?
A: QTc should be measured in patients with syncope, family history of sudden death, or when prescribing medications known to prolong QT interval.

Q4: Are there limitations to Bazett formula?
A: Bazett formula may overcorrect at high heart rates and undercorrect at low heart rates. Other formulas like Fridericia may be used in certain cases.

Q5: Should QTc be used alone for diagnosis?
A: QTc should be interpreted in clinical context along with other findings. Repeated measurements and clinical correlation are important.