1. What Is The Corrected QT Interval?

The corrected QT interval (QTc) is a heart rate-adjusted measure of the QT interval from an electrocardiogram (ECG). It accounts for variations in heart rate to provide a standardized measurement of ventricular repolarization.

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: If QT = 400 ms and HR = 60 bpm (RR = 1 s), then QTc = 400 / √1 = 400 ms.

3. Importance Of QTc Calculation

Details: Accurate QTc measurement is crucial for assessing cardiac repolarization abnormalities, identifying risk of arrhythmias, and monitoring medication effects that may prolong QT interval.

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 may indicate prolonged QT syndrome.

Q2: Why correct QT interval 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 formulas for QTc calculation?
A: Yes, other formulas include Fridericia's (QTc = QT / ∛RR) and Framingham (QTc = QT + 0.154(1-RR)), but Bazett's is most commonly used.

Q4: When should QTc be measured?
A: QTc should be measured during routine ECG interpretation, before starting medications that may prolong QT, and in patients with syncope or family history of sudden cardiac death.

Q5: What factors can affect QT interval?
A: Electrolyte imbalances, medications, genetic factors, heart disease, and autonomic nervous system activity can all affect QT interval duration.