QTc Correction Calculator Mayo

Mayo Clinic QTc Formula:

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

QT Interval (ms):

Heart Rate (HR):

bpm

Gender:

Age:

years

Corrected QT Interval (QTc):

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1. What is the QTc Correction Calculator?

The QTc Correction Calculator uses Bazett's formula to correct the QT interval for heart rate, providing a standardized measure of ventricular repolarization. This is essential for detecting abnormal cardiac rhythms and assessing arrhythmia risk.

2. How Does the Calculator Work?

The calculator uses Bazett's formula:

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

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 adjusts the QT interval for heart rate variations, providing a standardized QTc value 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, monitoring drug effects on cardiac repolarization, and guiding clinical management of cardiac patients.

4. Using the Calculator

Tips: Enter QT interval in milliseconds, heart rate in bpm, select gender and enter age. All values must be valid (QT > 0, HR > 0, age between 1-120). The calculator provides age and gender-specific normal ranges.

5. Frequently Asked Questions (FAQ)

Q1: Why use Bazett's formula for QTc correction?
A: Bazett's formula is the most widely used and clinically validated method for QT correction, though it may overcorrect at very high 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 standard 12-lead ECGs, preferably during stable heart rates, and repeated if abnormal or borderline.

Q4: Are there limitations to Bazett's formula?
A: The formula may overcorrect at high heart rates (>100 bpm) and undercorrect at low heart rates (<60 bpm). Alternative formulas may be used in these cases.

Q5: Why include gender and age in the calculation?
A: Normal QTc values vary by gender and age. Women typically have slightly longer QTc intervals, and normal ranges may differ in pediatric and elderly populations.