elektrocardiogram

An electrocardiogram, also spelled elektrokardiogram or elektrokardiogramm in some languages, is a noninvasive diagnostic test that records the electrical activity of the heart over time. It provides information about heart rate, rhythm, and the timing of electrical impulses that coordinate heartbeats.

The test is performed by attaching small electrodes to the skin on the chest and limbs. A standard 12-lead electrocardiogram uses 10 electrodes to generate 12 views of the heart’s electrical activity, allowing clinicians to assess atrial and ventricular activity, conduction pathways, and overall cardiac function. The recording shows waveforms, including the P wave (atrial depolarization), the QRS complex (ventricular depolarization), and the T wave (ventricular repolarization). Intervals such as the PR interval and QT interval provide additional timing information.

Typical indications include evaluation of chest pain or shortness of breath, assessment of palpitations or syncope, monitoring of known heart conditions, preoperative risk assessment, and evaluation of drug effects or electrolyte disturbances. In some settings, ambulatory versions are used, such as a Holter monitor (recording over 24–72 hours) or event monitors for intermittent symptoms.

Interpretation requires clinical context. An ECG can suggest arrhythmias, ischemia, infarction, conduction blocks, or electrolyte abnormalities, but a normal ECG does not exclude heart disease. Artifacts from movement, poor electrode contact, or interference can affect results, so proper technique and repeat measurements may be needed.

Historically, the electrocardiogram was developed in the early 20th century by Willem Einthoven, whose work laid the foundation for modern cardiac electrophysiology. The test remains a cornerstone of cardiovascular assessment.