Corrected QTC Calculator

QT:

 

QTc Bazett:
QTc Fredericia:
QTc Framingham
QTc Hodges:

 

QTc Calculator – Estimate Corrected QT Interval

The QTc Calculator is a powerful tool used by healthcare professionals to determine the corrected QT interval on an ECG (electrocardiogram). It adjusts the QT interval based on the heart rate, allowing for a more accurate assessment of cardiac repolarization. Abnormal QTc intervals can signal a risk of life-threatening arrhythmias.

What is QTc?

QTc stands for Corrected QT Interval. The QT interval represents the time taken for the ventricles of the heart to depolarize and repolarize, and it varies with heart rate. The QTc corrects this value to eliminate the effect of heart rate fluctuations, offering a standardized measure. It is especially critical when diagnosing Long QT Syndrome and monitoring medications that can prolong QT interval.

How to Use the QTc Calculator

  1. Enter the QT interval (in milliseconds) from the ECG.
  2. Input the heart rate (in beats per minute).
  3. Select the correction formula: Bazett's, Fridericia's, or Framingham.
  4. Click "Calculate" to get the QTc value.

QTc Formulas

The QTc is calculated using different formulas. Below are the most commonly used:

  • Bazett’s Formula: QTc = QT / √RR
  • Fridericia’s Formula: QTc = QT / ∛RR
  • Framingham’s Formula: QTc = QT + 0.154 × (1 − RR)

Note: RR interval = 60 / Heart Rate (in seconds)

Example Calculation

Suppose a patient has a QT interval of 400 ms and a heart rate of 75 bpm. Using Bazett’s Formula:

RR = 60 / 75 = 0.8 seconds  
QTc = 400 / √0.8 = 400 / 0.8944 ≈ 447 ms

Why Use the QTc Calculator?

  • Quick and accurate assessment of heart health.
  • Helps identify risk for ventricular arrhythmias.
  • Vital in pre-surgical evaluation and drug monitoring.
  • Used in cardiology, emergency medicine, and primary care.

Who Should Use This Tool?

  • Cardiologists
  • Emergency room doctors
  • Nurses and technicians conducting ECGs
  • Pharmacologists monitoring QT-prolonging drugs
  • Medical students and interns

Related Calculators

FAQs About QTc Calculator

1. What is a normal QTc value?

Normal QTc values are typically less than 440 ms for men and less than 460 ms for women. Values above this may indicate prolonged QT syndrome.

2. Which QTc formula is best?

Bazett’s formula is widely used, but Fridericia’s is often more accurate at higher heart rates. The choice depends on the clinical scenario.

3. Can QTc vary with medication?

Yes, many medications can prolong the QT interval. It’s crucial to monitor QTc in patients taking drugs known to affect heart rhythm.

4. Is this tool suitable for children?

QTc interpretation in children can differ. Use pediatric-specific QTc norms and consult a specialist when necessary.

5. What happens if QTc is too long?

Prolonged QTc increases the risk of Torsades de Pointes and sudden cardiac death. It requires prompt clinical evaluation.