Electrocardiography

Electrocardiography (ECG or EKG) is the process of recording the electrical activity of the heart over a period of time using electrodes placed on the skin. These electrodes detect the tiny electrical changes on the skin that arise from the heart muscle's electrophysiologic pattern of depolarizing and repolarizing during each heartbeat. It is a commonly performed cardiology test.

History

The development of electrocardiography is attributed to several key figures. Willem Einthoven, a Dutch physiologist, is often credited with inventing the first practical electrocardiogram in 1903. He introduced the term "electrocardiogram" and developed the Einthoven's triangle, which is a theoretical construct used to understand the electrical activity of the heart.

Principles

Electrocardiography works on the principle that the heart generates electrical impulses that spread throughout the body. These impulses can be detected by electrodes placed on the skin. The standard ECG uses 12 leads, which provide different views of the heart's electrical activity. The leads are placed on the limbs and the chest.

Components of an ECG

An ECG tracing consists of several key components:

• P wave: Represents atrial depolarization.
• QRS complex: Represents ventricular depolarization.
• T wave: Represents ventricular repolarization.
• U wave: Sometimes seen following the T wave, its origin is not well understood.

Clinical Uses

Electrocardiography is used to diagnose a variety of heart conditions, including:

• Arrhythmia
• Myocardial infarction
• Pericarditis
• Cardiomyopathy
• Electrolyte imbalance

Procedure

The procedure for performing an ECG is straightforward. The patient is asked to lie down, and electrodes are attached to the skin at specific locations. The machine then records the electrical activity of the heart, which is displayed as a series of waves on a monitor or printed on paper.

Interpretation

Interpreting an ECG requires understanding the normal patterns of the heart's electrical activity and recognizing deviations from these patterns. This includes analyzing the rate, rhythm, and morphology of the waves and complexes.

Limitations

While ECG is a valuable diagnostic tool, it has limitations. It may not detect all heart conditions, and some abnormalities may require further testing, such as an echocardiogram or stress test.

See Also

• Cardiology
• Heart
• Arrhythmia
• Myocardial infarction
• Echocardiogram
• Stress test