Mayo Clinic QTc Calculator

Bazett's Formula:

\[ QTc = \frac{QT}{\sqrt{RR}} \]

QT Interval (ms):

Heart Rate (HR):

bpm

Gender:

Age:

years

Corrected QT Interval (QTc):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What Is The Mayo Clinic QTc Calculator?

The Mayo Clinic QTc Calculator uses Bazett's formula to calculate the corrected QT interval, adjusted for rhythm, gender, and age-specific normals. It provides a standardized measurement of ventricular repolarization that accounts for heart rate variations.

2. How Does The Calculator Work?

The calculator uses Bazett's formula:

\[ QTc = \frac{QT}{\sqrt{RR}} \]

Where:

\( QT \) — QT interval measured from start of Q wave to end of T wave (ms)
\( RR \) — RR interval calculated as 60 / HR (seconds)
\( HR \) — Heart rate (beats per minute)

Explanation: The formula corrects the measured QT interval for heart rate, providing a standardized QTc value that can be compared across different heart rates and patient populations.

3. Importance Of QTc Calculation

Details: Accurate QTc calculation is crucial for assessing cardiac repolarization abnormalities, identifying patients at risk for arrhythmias, monitoring drug effects on cardiac conduction, and evaluating various cardiac conditions.

4. Using The Calculator

Tips: Enter QT interval in milliseconds, heart rate in beats per minute, select gender and enter age. All values must be valid (QT > 0, HR > 0, age between 0-120).

5. Frequently Asked Questions (FAQ)

Q1: Why Use Bazett's Formula For QTc Calculation?
A: Bazett's formula is the most widely used and clinically validated method for heart rate correction of the QT interval, though it may overcorrect at very high heart rates.

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

Q3: How Should QT Interval Be Measured?
A: QT interval should be measured from the beginning of the QRS complex to the end of the T wave, preferably in lead II or V5, and averaged over multiple beats.

Q4: Are There Limitations To Bazett's Formula?
A: The formula may overcorrect at high heart rates and undercorrect at low heart rates. Alternative formulas like Fridericia's may be used in specific situations.

Q5: Why Consider Gender And Age In QTc Interpretation?
A: Women typically have longer QTc intervals than men, and QTc may vary with age. Gender and age adjustments provide more accurate reference ranges.