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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...

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 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...

Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias III: Characteristics of Dysrhythmias

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 minute.

Voltammetric Techniques: Pulse Voltammetry

Voltammetric Techniques: Pulse Voltammetry

Differential-pulse voltammetry (DPV) is a type of voltammetry that involves applying a series of voltage pulses to an electrochemical cell while measuring the resulting current. In DPV, the differential pulse or small potential pulses are superimposed on a linear potential sweep. The magnitude of these pulses is typically small, often in the millivolt range. Each voltage pulse lasts a short duration, usually in the order of a few milliseconds, and is applied at regular intervals along the...

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Related Experiment Video

Updated: Jun 8, 2026

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

Published on: April 26, 2015

Comparison between two defibrillation waveforms.

Jecho Kostov¹, Tsvetan Mudrov, Ivan Dotsinsky

¹Centre of Biomedical Engineering Prof. Ivan Daskalov, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.

Journal of Medical Engineering & Technology

|September 23, 2010

Summary

This summary is machine-generated.

Comparing defibrillation waveforms, this study found no single optimal shape. Chopped biphasic pulses offer practical advantages for portable devices, while constant current pulses show higher energy efficiency in specific low-resistance scenarios.

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High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Published on: July 29, 2011

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Last Updated: Jun 8, 2026

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

Published on: April 26, 2015

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Published on: July 29, 2011

Area of Science:

Biomedical Engineering
Electrical Engineering
Cardiology

Background:

Defibrillation waveform selection is critical for effective cardiac resuscitation.
Optimizing energy delivery and device portability are key challenges in defibrillator design.

Purpose of the Study:

To compare the energy efficiency and practical implementation of chopped biphasic and constant current defibrillation waveforms.
To introduce metrics for evaluating waveform performance and capacitor energy utilization.

Main Methods:

Assessment of two defibrillation waveforms: chopped biphasic pulses and constant current pulses.
Introduction of two indices: W/W(0) for delivered energy ratio and η(C) for capacitor energy utilization.
Discussion of design considerations and capacitor selection for pulse generation.

Main Results:

No single defibrillation waveform demonstrated outstanding superiority across all parameters.
Constant current waveforms exhibited a higher W/W(0) ratio, particularly with patient resistance below 80 Ω.
Chopped biphasic waveforms present simpler technical implementation, enabling smaller and lighter portable defibrillators.

Conclusions:

Waveform choice involves a trade-off between energy efficiency and technical feasibility.
Chopped biphasic waveforms are suitable for portable defibrillators due to their simpler design.
Constant current waveforms may offer benefits in specific low-resistance conditions but face implementation challenges.