1. What is QTc?

The QTc interval is the QT interval corrected for heart rate using Bazett's formula. It's used to assess ventricular repolarization and identify potential arrhythmia risks.

2. How Does the Calculator Work?

The calculator uses Bazett's formula:

Where:

• \( QT \) — Measured QT interval in milliseconds
• \( RR \) — RR interval in seconds

Explanation: The formula accounts for the inverse relationship between heart rate and QT interval duration.

3. Importance of QTc Calculation

Details: Corrected QT interval is crucial for diagnosing long QT syndrome, assessing drug-induced QT prolongation, and evaluating arrhythmia risk.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and RR interval in seconds. Both values must be positive numbers.

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 >500 ms are associated with high arrhythmia risk.

Q2: How do I measure RR interval?
A: RR interval can be calculated as 60/heart rate (for HR in bpm) or measured directly from ECG as the distance between R waves.

Q3: Are there limitations to Bazett's formula?
A: Yes, it tends to overcorrect at high heart rates and undercorrect at low heart rates. Alternative formulas (Fridericia, Hodges) may be better in these cases.

Q4: When should QTc be measured?
A: QTc should be assessed before starting medications that may prolong QT interval, in syncope evaluation, and in family history of sudden cardiac death.

Q5: What causes prolonged QTc?
A: Causes include congenital long QT syndrome, medications, electrolyte abnormalities (hypokalemia, hypomagnesemia), and myocardial ischemia.