This calculator employs advanced AI algorithms to adjust the QT interval based on the patient's heart rate, providing a more accurate QTc value. The QTc is crucial for identifying potential risks of arrhythmias and other cardiac issues. By utilizing this tool, clinicians can streamline their assessment processes, improve patient safety, and make informed decisions regarding treatment options.
Patient Data Entry Guide
Step 1: Input ECG Values
- QT Interval: Enter value + unit (ms).
- Example:
400 ms
- Example:
- Heart Rate (HR): Enter value in beats per minute (bpm).
- Example:
80 bpm
- Example:
Step 2: Input Demographic Data
- Age: Enter age in years.
- Example:
45
- Example:
- Sex: Specify Male/Female/Other.
- Example:
Female
- Example:
Step 3: Select Formula
- Equation: Choose a correction formula:
- Bazett (1920)
- Fridericia (1920)
- Framingham (1992)
- Hodges (1983)
- Rautaharju (2009)
Step 4: Input Symptoms
- Symptoms: Describe symptoms or clinical concerns.
- Example:
Palpitations, syncope, dizziness
- Example:
Sample Diagnostic Report
QTc Calculation
- QT Interval: 400 ms
- Heart Rate: 80 bpm
- Age: 45 years
- Sex: Female
- Selected Formula: Bazett
Interpretation
- QTc Classification: Prolonged (Female: Normal ≤460 ms).
- Arrhythmia Risk: Increased risk for torsades de pointes.
Symptom Correlation
- Syncope and palpitations may indicate arrhythmic events.
Recommendations
- Repeat ECG: Confirm QTc prolongation.
- Discontinue QT-Prolonging Drugs: Review medications (e.g., antibiotics, antipsychotics).
- Electrolyte Assessment: Check potassium, magnesium, and calcium levels.
- Cardiology Referral: For Holter monitoring or genetic testing if congenital long QT syndrome is suspected.
Key Considerations
- Formula Selection:
- Bazett: Overcorrects at high HR, undercorrects at low HR.
- Fridericia: Better accuracy for HR extremes (QTc = QT / RR<sup>1/3</sup>).
- Hodges: Adjusts for HR using linear regression (QTc = QT + 105*(1 - HR/60)).
- Rautaharju: Incorporates age/sex (preferred for automated ECG machines).
- Normal Ranges:
- Male: ≤450 ms | Female: ≤460 ms.
- Prolonged: >450 ms (Male), >460 ms (Female).
- Unit Conversions:
- HR to RR Interval: RR (seconds) = 60 / HR.
- Limitations:
- Formulas assume sinus rhythm; not valid for atrial fibrillation.
- Bazett: Avoid if HR <50 or >120 bpm.
Equations
Bazett Formula:
Fridericia Formula:
Hodges Formula:
Hodges Formula:
Rautaharju Formula:
QTc Classification
| QTc (ms) | Category | Clinical Action |
|---|---|---|
| ≤450 (M), ≤460 (F) | Normal | Monitor if symptomatic |
| 451–470 (M), 461–480 (F) | Borderline | Review medications, electrolytes |
| >470 (M), >480 (F) | Prolonged | Discontinue QT-prolonging drugs, urgent referral |
Final Diagnosis: Combines QTc, symptoms, and demographics to guide arrhythmia risk management (e.g., drug cessation in prolonged QTc with syncope).
✅ Formula Verification:
- Bazett Example: QT=400 ms, HR=80 → QTc=400 / √(0.75) ≈ 462 ms
- Hodges Example: QT=400 ms, HR=100 → QTc=400 + 105*(1 - 100/60) = 400 - 70 = 330 ms