1. What is Bazett's Formula?

Bazett's formula is used to calculate the corrected QT interval (QTc) which accounts for heart rate variations. It provides 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 (seconds)
• \( HR \) — Heart rate (beats per minute)

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

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing cardiac repolarization abnormalities, identifying risk of arrhythmias, and monitoring drug effects 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: 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 important in clinical practice?
A: Prolonged QTc is associated with increased risk of life-threatening ventricular arrhythmias, particularly torsades de pointes.

Q3: Are there limitations to Bazett's formula?
A: Bazett's formula may overcorrect at high heart rates and undercorrect at low heart rates. Other formulas (Fridericia, Framingham) may be used in specific situations.

Q4: When should QTc be measured?
A: QTc should be measured in patients taking medications known to prolong QT interval, those with syncope, or with family history of sudden cardiac death.

Q5: How should QTc 401 ms be interpreted?
A: A QTc of 401 ms is generally within normal limits for most adults, but interpretation should consider patient's age, sex, and clinical context.