1. What is QTc Interval?

The QTc (corrected QT) interval represents the QT interval adjusted for heart rate using Bazett's formula. It provides a standardized measure of ventricular repolarization that accounts for variations in heart rate.

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)

Example: QT=360 ms, RR=0.8 s (HR=75), QTc=403 ms.

3. Importance of QTc Calculation

Details: Accurate QTc measurement is crucial for assessing cardiac repolarization abnormalities, identifying risk of arrhythmias, and monitoring drug effects on cardiac conduction.

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 is typically <440 ms for men and <460 ms for women. Values above these may indicate prolonged QT syndrome.

Q2: Why correct QT for heart rate?
A: The QT interval naturally shortens with increasing heart rate. Correction allows comparison of QT values across different heart rates.

Q3: Are there alternative correction formulas?
A: Yes, other formulas include Fridericia's (QTc = QT/RR^1/3) and Framingham (QTc = QT + 0.154(1-RR)) corrections.

Q4: When is QTc measurement most important?
A: Particularly important when prescribing medications known to prolong QT interval, in patients with cardiac conditions, or when evaluating syncope.

Q5: What factors can affect QTc measurement?
A: Electrolyte imbalances, medications, cardiac disease, autonomic nervous system activity, and measurement technique can all affect QTc values.