calculate_qtc: Corrected QT Interval (QTc) Calculator

In cliot: Clinical Indices and Outcomes Tools

Corrected QT Interval (QTc) Calculator

Description

Calculates the Corrected QT Interval (QTc) using four standard formulas: Bazett, Fridericia, Framingham, and Hodges. The QTc adjusts the measured QT interval for heart rate, allowing for the assessment of repolarization abnormalities (e.g., Long QT Syndrome) regardless of the patient's pulse.

Usage

calculate_qtc(qt_interval_msec, heart_rate_bpm)

Arguments

qt_interval_msec	Numeric. The measured QT interval in milliseconds (from the beginning of the Q wave to the end of the T wave).
heart_rate_bpm	Numeric. The patient's heart rate in beats per minute.

Details

Formulas used:

• Bazett: QTc = QT / \sqrt{RR} (Most common, but overcorrects at high heart rates).

• Fridericia: QTc = QT / \sqrt[3]{RR}.

• Framingham: QTc = QT + 154 \times (1 - RR).

• Hodges: QTc = QT + 1.75 \times (HR - 60).

Where RR = 60 / HR.

Value

A list containing:

QTc_Bazett	QTc calculated via Bazett's formula.
QTc_Fridericia	QTc calculated via Fridericia's formula.
QTc_Framingham	QTc calculated via Framingham's formula.
QTc_Hodges	QTc calculated via Hodges' formula.

References

Bazett HC. An analysis of the time-relations of electrocardiograms. Heart. 1920;7:353-370. Fridericia LS. Die Systolendauer im Elektrokardiogramm bei normalen Menschen und bei Herzkranken. Acta Medica Scandinavica. 1920;53:469-486.

Examples

# Example 1: Normal Heart Rate
# QT 400 ms, HR 60 bpm (RR = 1 sec)
# All formulas should yield approx 400 ms
calculate_qtc(400, 60)

# Example 2: Tachycardia
# QT 320 ms, HR 100 bpm
# Bazett overcorrects compared to others
calculate_qtc(320, 100)

cliot documentation built on Dec. 1, 2025, 1:06 a.m.