electrocardiograph

An electrocardiograph is a medical device that records the electrical activity of the heart over time. The recorded signal is called an electrocardiogram. The term ECG is commonly used, especially in modern practice, while EKG reflects the German Elektrokardiogramm. The electrocardiograph is distinct from electrocardiography, the procedure of obtaining an ECG trace.

Electrodes are placed on the skin at standardized locations and connected to the instrument by leads. The heart’s electrical impulses generate voltages that are measured, amplified, and displayed as a tracing on paper or a digital screen. The typical waveform includes a P wave, QRS complex, and T wave, which relate to atrial depolarization, ventricular depolarization, and ventricular repolarization.

Modern electrocardiographs are digital, often part of multiparameter monitors. They can record a single-lead trace or a 12-lead ECG, which uses multiple electrode placements to provide different perspectives on cardiac electrical activity. Some devices store traces, print them on sheets, or transmit data to electronic health records.

Clinical use: The ECG is a routine test for evaluating chest pain, suspected arrhythmias, monitoring during surgery, preoperative screening, and routine health checks. It helps diagnose conditions such as myocardial infarction, atrial fibrillation, conduction blocks, and electrolyte disturbances that affect cardiac conduction.

Limitations and interpretation: The ECG reflects electrical activity, not direct mechanical function, and artefacts from movement or poor electrode contact can affect results. A tracing must be interpreted in conjunction with symptoms, history, and other tests. The instrument itself is a diagnostic tool, while clinical judgment determines management.

History: Early ECGs were recorded with a string galvanometer developed by Willem Einthoven in the early 20th century. The technology evolved from paper records to digital displays, and 12-lead systems became standard in many settings.