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MODULE TWO: QTc Risk - A Primer for
Healthcare Providers

Detecting Proarrhythmic ECG Changes

QTc Risk Clinical Decision Support: A Primer For Healthcare Providers

SECTION 1: Detecting Proarrhythmic ECG Changes

The first education module in a series of four — QTc Risk Clinical Decision Support: A Primer For Healthcare Providers — will focus on specific changes that occur within cardiac myocytes that lead to changes on the electrocardiogram. The information in this module is important to learn in order to recognize when patients are at risk for an arrhythmic event. 

At the conclusion of this module, you will be invited to take a short knowledge test to give you immediate feedback regarding your understanding of the provided material.




Electrophysiological Principles Review:

This module begins with a short review of the electrophysiological principles required to understand the requirements for capturing a precise reading of the heart’s electrical activity, including:

  • Examining the ionic currents that flow across the heart cell membrane during a heart beat.
  • How those currents affect the action potential of a myocyte
  • How these processes determine the waveform of an electrocardiogram recording from electrodes on the skin.
  • A discussion of the QRS caused by the depolarization of the ventricle followed by the T-wave which represents the movement of ions through potassium channels.

Major ECG Intervals/QT Intervals:

The second portion of this module delves deeper into the QT interval which represents the time taken for depolarization and complete repolarization for a heartbeat. This is followed by a review of the formulas traditionally used to correct the QT and their individual strengths and weaknesses.

Normal Range For a QT Interval

This section of the module will discuss the normal range of QTc intervals and examine variances in age and gender concerning longer QTc and how this contributes to greater incidences of torsades de pointes.

Torsades de Pointes

Following this discussion of QT intervals, the module will further explore torsades de pointes, what torsades de pointes looks like on a rhythm strip, and how to interpret torsades de pointes on a normal electrocardiogram.

Calculating QTc using the Bazett’s Formula

Finally, this module concludes with a review of the required formula for calculating QTc using Bazett’s formula and the advantages of using a web calculator to perform the calculation.

Coming Soon

Module 1: Cardiac Electrophysiology and Torsades de Pointes Knowledge Evaluation

Please enter the correct answer for each question:


1. Using the figure below, identify the beginning of the Q wave on the electrocardiogram.

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2. What is the duration of the uncorrected QT interval in terms of milliseconds for this patient?

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3. What duration is considered a prolonged QTc interval?

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4. Women have a significantly longer QT than men at most times throughout their lives.

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5. When correcting the QT based on the heart rate in order to normalize it to a common rate, we use a common rate of ?

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This project was supported by grant R18HS026662 from the Agency for Healthcare Research and Quality. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Agency for Healthcare Research and Quality.