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Electrocardiogram

Electrocardiogram

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 the T...

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

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

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...

ECG Interpretation of Rhythms

ECG Interpretation of Rhythms

An electrocardiogram (ECG)graphically represents the heart's electrical activity on ECG paper or a monitor.
Components of the Electrocardiogram
The primary components of a normal ECG waveform in Normal sinus rhythm(NSR) include the P wave, PR interval, QRS complex, ST segment, T wave, and occasionally a U wave.
ECG waveforms are divided by vertical and horizontal lines at standard intervals.
The horizontal axis measures time and rate, and the vertical axis measures amplitude or voltage. When...

Electrocardiogram Fundamentals

Electrocardiogram Fundamentals

Introduction
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
An ECG utilizes electrodes on the skin to...

Dysrhythmias V: Evaluating Dysrhythmias

Dysrhythmias V: Evaluating Dysrhythmias

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...

Correlation between ECG and Cardiac Cycle

Correlation between ECG and Cardiac Cycle

The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...

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Related Experiment Video

Updated: May 31, 2026

Electrocardiogram Recordings in Anesthetized Mice using Lead II

Electrocardiogram Recordings in Anesthetized Mice using Lead II

Published on: June 20, 2020

Electrocardiographic QT interval and mortality: a meta-analysis.

Yiyi Zhang¹, Wendy S Post, Elena Blasco-Colmenares

¹Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA.

Epidemiology (Cambridge, Mass.)

|June 29, 2011

Summary

A prolonged electrocardiographic QT interval, even within normal limits, is linked to increased risks of total, cardiovascular, coronary heart disease, and sudden cardiac death in the general population.

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Methods for ECG Evaluation of Indicators of Cardiac Risk, and Susceptibility to Aconitine-induced Arrhythmias in Rats Following Status Epilepticus

Methods for ECG Evaluation of Indicators of Cardiac Risk, and Susceptibility to Aconitine-induced Arrhythmias in Rats Following Status Epilepticus

Published on: April 5, 2011

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Last Updated: May 31, 2026

Electrocardiogram Recordings in Anesthetized Mice using Lead II

Electrocardiogram Recordings in Anesthetized Mice using Lead II

Published on: June 20, 2020

Methods for ECG Evaluation of Indicators of Cardiac Risk, and Susceptibility to Aconitine-induced Arrhythmias in Rats Following Status Epilepticus

Methods for ECG Evaluation of Indicators of Cardiac Risk, and Susceptibility to Aconitine-induced Arrhythmias in Rats Following Status Epilepticus

Published on: April 5, 2011

Area of Science:

Cardiology
Preventive Medicine
Public Health

Background:

Extremely prolonged QT intervals are known risk factors for malignant ventricular arrhythmias and sudden cardiac death.
The impact of normal variations in QT interval length on mortality in the general population remains unclear.

Purpose of the Study:

To investigate the association between QT interval length and mortality endpoints.
To clarify the prognostic value of QT interval variations within the normal range.

Main Methods:

A meta-analysis was conducted, synthesizing data from 23 observational studies.
Inverse-variance weighted random-effects models were employed to pool relative risks.

Main Results:

Higher QT interval length was associated with increased total mortality (RR 1.35), cardiovascular mortality (RR 1.51), coronary heart disease mortality (RR 1.71), and sudden cardiac death (RR 1.44).
A 50 ms increase in QT interval correlated with higher risks for total mortality (RR 1.20), cardiovascular mortality (RR 1.29), and coronary heart disease mortality (RR 1.49).

Conclusions:

Prolonged QT interval is consistently associated with elevated risks of various mortality outcomes.
QT interval length is a significant determinant of mortality in the general population.