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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...

Instrumentation Amplifier

Instrumentation Amplifier

An electrocardiography (ECG) machine is an essential piece of medical equipment used to monitor the electrical activity of the heart. It operates by detecting small electrical changes on the skin that result from the depolarization of the heart muscle during each heartbeat. However, these signals are in the microvolt range and can be easily overwhelmed by noise or interference.
To overcome this challenge, an ECG machine utilizes an instrumentation amplifier. This specialized amplifier is...

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...

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....

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...

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Electrocardiographs before 1910: Manufacturers and surviving instruments.

Olle Pahlm¹, Bengt Uvelius¹, Anders Widell²

¹Department of clinical sciences Lund, Lund University, Sweden.

Journal of Electrocardiology

|December 22, 2025

Summary

The Lund string galvanometer electrocardiograph, a rare and well-preserved device from 1909, highlights the importance of conserving early electrocardiography technology. This early diagnostic tool predates modern amplification methods.

Keywords:

ECG Einthoven History String galvanometer

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Area of Science:

Biomedical Engineering
Medical History
Instrumentation Science

Background:

Early electrocardiographs required highly sensitive instrumentation due to the absence of electronic amplification.
Willem Einthoven's 1903 string galvanometer revolutionized electrocardiography, enabling clinical diagnosis.

Purpose of the Study:

To detail the history and technical aspects of a complete string galvanometer system in Lund, Sweden.
To review the early commercial production and survival of string galvanometers made before 1910.

Main Methods:

The Lund electrocardiograph was analyzed and compared to historical records and Einthoven's laboratory documentation.
A survey of museum collections and manufacturers' archives was conducted to identify surviving early instruments.

Main Results:

The 1909 Lund string galvanometer, built from Einthoven's designs, retains its core components.
Commercial production was limited to Edelmann and Cambridge Scientific Instrument Company, with few surviving examples.

Conclusions:

Complete early electrocardiographs are exceptionally rare.
The Lund instrument is a significant surviving example, emphasizing the need for conservation of early biomedical technology.