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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...

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

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...

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Related Experiment Video

Updated: Apr 18, 2026

Noninvasive Electrocardiography in the Perinatal Mouse

Noninvasive Electrocardiography in the Perinatal Mouse

Published on: June 12, 2020

Electrocardiographic intervals in foetuses with CHD.

Betul Yilmaz¹, Hari K Narayan¹, Abigail Wilpers²

¹1Department of Pediatrics,Division of Pediatric Cardiology,Morgan Stanley Children's Hospital,Columbia University Medical Center,New York,United States of America.

Cardiology in the Young

|January 21, 2015

Summary

Fetal electrocardiographic intervals, including PR and QRS, lengthen with gestational age in healthy fetuses. Congenital heart disease fetuses show significantly longer QRS intervals from 20 weeks gestation.

Keywords:

Foetal electrocardiography congenital heart disease electrocardiographic intervals

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Last Updated: Apr 18, 2026

Noninvasive Electrocardiography in the Perinatal Mouse

Noninvasive Electrocardiography in the Perinatal Mouse

Published on: June 12, 2020

Fetal Mouse Cardiovascular Imaging Using a High-frequency Ultrasound 30/45MHZ System

Fetal Mouse Cardiovascular Imaging Using a High-frequency Ultrasound 30/45MHZ System

Published on: May 5, 2018

Murine Fetal Echocardiography

Murine Fetal Echocardiography

Published on: February 15, 2013

Area of Science:

Cardiology
Prenatal Diagnosis
Fetal Medicine

Background:

Congenital heart disease (CHD) is a significant concern in prenatal diagnostics.
Understanding fetal electrocardiographic (FECG) intervals can aid in early detection.
Gestational age-specific norms for FECG intervals are crucial for interpretation.

Purpose of the Study:

To evaluate fetal electrocardiographic intervals (PR, QRS, QT) across gestational ages in fetuses with and without CHD.
To identify differences in these intervals between fetuses with and without CHD.
To establish if FECG intervals can differentiate between normal and CHD fetuses early in gestation.

Main Methods:

A prospective observational cohort study included 92 participants (41 controls, 51 with CHD).
FECG was serially obtained using maternal abdominal monitoring at 20-24, 28-32, and 34-38 weeks gestation.
Signal-averaged waveforms were analyzed to measure PR, QRS, and QT intervals, with statistical comparisons between groups.

Main Results:

PR and QRS intervals correlated with gestational age in control fetuses (p<0.05).
QRS intervals were significantly longer in fetuses with CHD compared to controls at all measured gestational ages (p<0.001 at 20-24 weeks).
Differences in QRS intervals were detectable as early as 20 weeks gestation.

Conclusions:

Fetal PR and QRS intervals normally lengthen with advancing gestational age.
Fetuses with CHD exhibit prolonged QRS intervals compared to controls.
FECG analysis can identify fetuses with CHD as early as 20 weeks gestation, aiding in prenatal diagnosis.