ECG
Meaning of ECG: Ten electrodes produce twelve views of the same heartbeat, each looking at the heart from a different direction.
Definition of ECG
ECG stands for electrocardiogram, a recording of the electrical activity that drives each heartbeat. Adhesive electrodes placed on the chest, arms and legs pick up the tiny voltage changes spreading through the heart muscle, and a machine plots them as a tracing. The test is quick and painless and involves no radiation or injection.
What does the tracing show?
Each beat begins in a small patch of tissue in the upper right chamber that fires on its own, and the resulting wave of electrical activity spreads through the heart in a set order. That order appears on the paper as a repeating shape. A small first bump marks the upper chambers contracting. A tall sharp spike marks the far more muscular lower chambers contracting, which is the beat that can be felt at the wrist. A rounded wave afterward marks the lower chambers resetting electrically before the next beat. Reading an electrocardiogram means checking the rate, the regularity, the shape of each part and the intervals between them, across all twelve views.
What can it detect?
| Pattern on the tracing | What it points toward |
|---|---|
| Irregular rhythm with the first bump absent | Atrial fibrillation and related rhythm disturbances |
| Shifts in the segment and wave that follow the main spike | Heart muscle short of blood, including a heart attack in progress |
| Widened or delayed complexes | A block along the heart's conducting pathways |
| Peaked or flattened resetting waves | Shifts in potassium and other electrolytes |
| Unusually tall complexes | Thickened heart muscle, as develops in long-standing high blood pressure |
Its main limitation is that it captures only the seconds during which it runs. A normal tracing does not rule out coronary artery disease, and an intermittent rhythm problem is easily missed, which is why recordings worn for a day or longer are used when symptoms come and go. Enlargement seen on a tracing is also inferred from voltages rather than measured, so a suspicion of congestive heart failure is confirmed by imaging rather than by the ECG alone.
Why is it sometimes spelled EKG?
EKG comes from the German Elektrokardiogramm, and the spelling entered English along with much of the early work on the technique. Both abbreviations mean exactly the same test. EKG is still widely used in speech in the United States, partly because it is harder to confuse with EEG, the recording of brain activity, when the two are said aloud.
Also known as
Used in a sentence
An ECG was obtained promptly after the patient reported chest pain.
Good to know
An ECG, which records the heart's electrical activity, is a distinct test from an echocardiogram, which uses ultrasound to visualize the heart's structure and pumping function, despite the similar-sounding names.
Word origin
Where “ECG” comes from
Electrocardiogram is built from Greek elektron, meaning amber, the substance that gave electricity its name, with kardia, meaning heart, and gramma, meaning something written.