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Related Concept Videos

Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

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Arrhythmia or dysrhythmia refers to an abnormal heart rhythm caused by a defect in the heart's conduction system. It can cause the heart to beat irregularly, too quickly, or too slowly, leading to symptoms like chest pain, shortness of breath, and fainting. Factors such as stress, caffeine, alcohol, nicotine, cocaine, certain drugs, congenital defects, diseases, and electrolyte abnormalities can trigger arrhythmias.
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
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Dysrhythmias V: Evaluating Dysrhythmias01:30

Dysrhythmias V: Evaluating Dysrhythmias

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Dysrhythmias, also known as arrhythmias, are disturbances in the heart's rhythm that range from benign to life-threatening. A thorough evaluation is crucial for appropriate management and involves a comprehensive medical history, physical examination, and various diagnostic tests.Medical HistorySymptoms: Collect detailed information on palpitations, dizziness, syncope, chest pain, and fatigue. Note their onset, frequency, and triggers.Previous Cardiac Issues: Document any history of heart...
239
Dysrhythmias III: Characteristics of Dysrhythmias01:29

Dysrhythmias III: Characteristics of Dysrhythmias

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Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:Sinus Tachycardia:Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per...
306
Dysrhythmias II: Classification of Tachyarrhythmias01:28

Dysrhythmias II: Classification of Tachyarrhythmias

381
Tachyarrhythmias are a type of dysrhythmia where the heart rate exceeds 100 beats per minute. Here are some common types of tachyarrhythmias:Sinus TachycardiaSinus tachycardia originates from increased impulses from the sinus node, leading to an elevated heart rate. It is often triggered by stress, fever, or exercise.Patients may experience palpitations, a sensation of a racing heart, dizziness, and chest discomfort.Causes and Risk Factors: Common causes include physical exertion, emotional...
381
ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias

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Arrhythmia is a condition characterized by an irregular heart rhythm, with ECG changes that differ based on its origin and nature. The types of arrhythmias discussed below include atrial, junctional, and ventricular arrhythmias.Atrial ArrhythmiasPremature Atrial Complexes (PACs): PACs are early atrial beats caused by stress, caffeine, alcohol, electrolyte imbalances, hypoxia, hyperthyroidism, or certain medications (e.g., bronchodilators and decongestants). The ECG shows early P waves with an...
349
Electrocardiogram01:29

Electrocardiogram

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An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...
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Related Experiment Video

Updated: Dec 22, 2025

Measurement of Heart Contractility in Isolated Adult Human Primary Cardiomyocytes
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T-wave alternans testing for ventricular arrhythmias.

Sanjiv M Narayan1

  • 1University of California and VA Medical Center, La Jolla, CA, USA. snarayan@ucsd.edu

Progress in Cardiovascular Diseases
|September 9, 2008
PubMed
Summary

T-wave alternans (TWA) predicts life-threatening ventricular arrhythmias by measuring ECG T-wave fluctuations. Integrating TWA with existing risk factors improves sudden cardiac arrest risk stratification.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Medical Technology

Background:

  • T-wave alternans (TWA) quantifies beat-to-beat variations in the electrocardiogram (ECG) T-wave.
  • TWA has shown potential in predicting ventricular arrhythmias across diverse patient groups.
  • Understanding repolarization alternans at cellular and tissue levels is crucial for clinical application.

Purpose of the Study:

  • To review the literature connecting cellular and tissue-level repolarization alternans with clinical TWA findings.
  • To evaluate TWA's additive value to existing risk factors for predicting ventricular arrhythmias.
  • To propose an evidence-based framework for integrating TWA into sudden cardiac arrest risk stratification.

Main Methods:

  • Literature review of cellular, tissue, and clinical studies on T-wave alternans.

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  • Analysis of TWA's predictive performance in conjunction with established clinical risk factors.
  • Development of a framework for integrating TWA into risk stratification models.

    • Main Results:

    • TWA successfully adds predictive value to existing clinical risk factors for ventricular arrhythmias.
    • Evidence supports the link between cellular/tissue-level alternans and clinical TWA observations.
    • The reviewed literature demonstrates TWA's utility in risk assessment.

    Conclusions:

    • T-wave alternans is a valuable biomarker for predicting ventricular arrhythmias.
    • Integrating TWA into risk stratification models can enhance the prediction of sudden cardiac arrest.
    • Further research can refine the clinical application of TWA for improved patient outcomes.