QTc Calculator Paeds

Bazett's Formula:

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

Corrected QT (QTc):

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1. What is Bazett's Formula?

Bazett's formula is used to calculate the corrected QT interval (QTc) by accounting for heart rate variations. It is particularly important in pediatric cardiology to assess the risk of arrhythmias.

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 (s)
\( HR \) — Heart rate (bpm)

Explanation: The formula corrects the QT interval for heart rate, providing a standardized measure 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, and monitoring medication effects on cardiac repolarization in children.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and heart rate in beats per minute. Normal QTc is <440 ms in children. All values must be valid (QT > 0, HR > 0).

5. Frequently Asked Questions (FAQ)

Q1: Why is QTc important in pediatric patients?
A: QTc helps identify children at risk for life-threatening arrhythmias, particularly those with congenital long QT syndrome or on medications that prolong QT interval.

Q2: What is considered a normal QTc in children?
A: Normal QTc is generally <440 ms in children. Values between 440-460 ms are borderline, and >460 ms are considered prolonged.

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: Bazett's formula may overcorrect at high heart rates and undercorrect at low heart rates. Alternative formulas (Fridericia, Hodges) may be used in certain situations.

Q5: When should QTc monitoring be performed?
A: QTc should be monitored in children taking medications known to prolong QT interval, those with syncope or family history of sudden cardiac death, and in suspected congenital long QT syndrome.