Electrocardiogram

Lore & Background

Electrocardiography began in the late 19th century with the discovery of the heart's electrical activity. Willem Einthoven's 1903 string galvanometer enabled precise measurement of these signals, revolutionizing cardiography; he received the 1924 Nobel Prize for this work. Early ECG machines used analog electronics to print signals onto paper, while modern machines use analog-to-digital converters and often include automated interpretation algorithms, though computer misinterpretation remains a significant problem.

Reader's Guide

The electrocardiogram is a cornerstone of cardiac diagnosis, providing information about heart rate, rhythm, chamber size, muscle damage, drug effects, and pacemaker function. It is used in settings ranging from emergency evaluation of chest pain to perioperative monitoring and cardiac stress testing. Continuous monitoring via Holter monitors or implantable devices captures infrequent arrhythmias. Despite its utility, screening asymptomatic adults is not supported due to risks of false positives and overtreatment. The ECG remains essential for detecting conditions like atrial fibrillation, myocardial infarction, and electrolyte disturbances, and its interpretation requires expert verification of automated results.

Did You Know?

• A conventional 12-lead ECG uses ten electrodes placed on the limbs and chest to measure the heart's electrical potential from twelve angles over about ten seconds.
• The three main components of an ECG are the P wave (atrial depolarization), QRS complex (ventricular depolarization), and T wave (ventricular repolarization).
• ECG machines include defibrillation protection and electrostatic discharge protection up to 18,000 volts.
• Portable ECG devices, such as Holter monitors and smartwatches, can record heart activity using as few as two electrodes.