EKG
Meaning of EKG: Quick, painless and available almost anywhere, it is usually the first test reached for when the heart is the question.
Definition of EKG
An EKG is a recording of the electrical activity that drives each heartbeat, captured through electrodes placed on the skin and drawn as a tracing of voltage against time. The signal spreading through heart muscle before it contracts produces a repeating pattern of waves, and the shape, timing and spacing of those waves carry the diagnostic information.
What do the waves mean?
| Part of the tracing | What it represents |
|---|---|
| P wave | The signal spreading across the upper chambers, the atria |
| PR interval | The pause at the junction between upper and lower chambers |
| QRS complex | The signal spreading across the lower chambers, the ventricles |
| T wave | The ventricles recovering electrically before the next beat |
| QT interval | The whole span from ventricular activation to recovery |
A standard recording views this activity from twelve directions at once, using electrodes on the limbs and across the chest. Each view looks at the same electrical event from a different angle, so a change confined to particular views points to the region of heart muscle involved.
What can it show?
Abnormal rhythms are the most direct finding, since the tracing shows exactly where each signal starts and how it travels. It also shows delays or blocks in the conducting pathways, thickening or enlargement of a chamber, patterns indicating reduced blood flow to cardiac muscle or a heart attack in progress, and the scar left by an old one. Some electrolyte disturbances, especially of potassium and calcium, alter wave shape in recognizable ways, as do certain medicines and inherited conditions that lengthen the QT interval.
What can it not show?
It records electricity, not mechanics. Pumping strength, valve function and blood flow do not appear on it, so a tracing can look entirely normal in someone with severe congestive heart failure or a leaking valve; those questions need an ultrasound of the heart. A routine recording also captures only a few seconds, so a rhythm disturbance that comes and goes is easily missed, which is why longer monitoring over hours or days exists. And a normal tracing does not exclude narrowed coronary arteries when the heart is at rest.
Also known as
Used in a sentence
An EKG was obtained to evaluate the patient's reported chest pain and irregular heartbeat.
Good to know
EKG and ECG name the same test and are used interchangeably, with EKG reflecting the German spelling elektrokardiogramm that shaped the original abbreviation.
Word origin
Where “EKG” comes from
The abbreviation follows the German Elektrokardiogramm, built from Greek kardia, meaning heart, and gramma, meaning something written.