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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...

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...

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....

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...

Holter Monitor: 24-Hour Monitoring

Holter Monitor: 24-Hour Monitoring

Holter monitoring is a continuous electrocardiography (ECG) recording that tracks the heart's electrical activity over an extended period, generally 24 to 48 hours. This noninvasive diagnostic tool detects irregular heart rhythms that may not be captured during a standard ECG performed in a clinical setting.DeviceThe Holter monitor is a portable, small device connected to several electrodes on the patient's chest. These electrodes detect the heart's electrical signals and transmit them to the...

Cardiac Action Potential

Cardiac Action Potential

Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials

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Related Experiment Video

Updated: Dec 27, 2025

Analyzing Long-Term Electrocardiography Recordings to Detect Arrhythmias in Mice

Analyzing Long-Term Electrocardiography Recordings to Detect Arrhythmias in Mice

Published on: May 23, 2021

Long-term ECG recording: findings and implications.

Jarle Jortveit, Trond Helge Lislevand, Lars Rysstad

Tidsskrift for Den Norske Laegeforening : Tidsskrift for Praktisk Medicin, Ny Raekke

|February 28, 2020

Summary

Long-term ECG recordings are frequently used but often yield few therapeutic results. The study suggests using this diagnostic tool more selectively for patients who could benefit from treatment based on findings like atrial fibrillation.

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Area of Science:

Cardiology
Medical Diagnostics

Background:

Long-term electrocardiogram (ECG) recording is a prevalent diagnostic tool.
Current guidelines lack clarity on patient selection for long-term ECG.
There is a need for an overview of test outcomes and their therapeutic impact.

Purpose of the Study:

To evaluate the utilization and clinical implications of long-term ECG recordings.
To assess the diagnostic yield and therapeutic impact of long-term ECG in a real-world setting.

Main Methods:

Retrospective review of 1,262 long-term ECG recordings from Sørlandet Hospital Arendal (2017-18).
Data collected included patient demographics, referral indications, test results, and subsequent management.
Analysis focused on the prevalence of arrhythmias and therapeutic implications of the findings.

Main Results:

20% of recordings detected arrhythmias; 13% led to therapeutic interventions.
In patients without prior heart disease or stroke history (49% of cohort), only 5% of tests had therapeutic implications.
The majority of tests were performed on patients with limited likelihood of significant findings.

Conclusions:

Long-term ECG is often employed in patient groups where positive findings are infrequent and unlikely to alter management.
Findings suggest a need for more targeted application of long-term ECG, particularly in patients with indications for treatment based on potential arrhythmia detection (e.g., atrial fibrillation for stroke prevention).