Electrocardiogram

ECG may also refer to the East Coast Greenway.

Lead II

An Electrocardiogram (abbreviated as either ECG or EKG (from German, Elektrokardiogramm)) is a graphic produced by an electrocardiograph, which records the electrical current in the heart in the form of a continuous strip graph. The ECG results provide the follwing:

Determine whether the heart is performing normally or suffering from abnormalities (eg. extra or skipped heartbeats - Cardiac arrhythmia).
May indicate coronary artery blockages (especially when the patient is stressed).
Can be used for detecting calcium, magnesium and other imbalances.
Allows the detection of conduction abnormalities.
Indicates the physical shape of a patient during stress tests.
Can provide information on the physical condition of the heart.

Table of contents

1 Details
2 Notes
3 Related topics

Details

A typical ECG tracing of a normal heartbeat consists of a p wave, a qrs complex and a t wave. The p wave is the electrical signature of the current that causes atrial contraction. Both the left and right atria contract simultaneously. The qrs complex corresponds to the current that causes contraction of the ventricles, which is much more forceful than that of the atria and involves more muscle area, thus resulting in a much greater ECG deflection. The qrs complex contains the atrial repolarization current. The t wave represents the repolarization of the ventricles. Electrically, the cardiac muscle cells are like loaded springs. A small impulse sets them off, they depolarize and contract. Setting the spring up again is repolarization (more at action potential).

Lead I

A typical ECG report shows the cardiac cycle from 12 different vantage points, like viewing the event elecrically from 12 different directions. Understanding the usual and abnormal directions, or vectors, of depolarization and repolarization yields important diagnostic information. The directions, or vectors, are known as leads. The inferior leads are II, III and aVF, the lateral leads are I and aVL. The chest, or anterior leads are V1 through V6. aVR is rarely used for diagnostic information, but indicates if the ECG leads were placed correctly on the patient. Inferior, lateral and anterior refer to portions of the heart. The inferior leads record events from the apex of the left ventricle. The lateral and anterior leads record events from the left wall and front walls of the left ventricle, respectively. The right ventricle has very little muscle mass. It leaves only a small imprint on the ECG, making it more difficult to diagnose than changes in the right ventricle.

Notes

The device has become so familiar with its depiction in various television medical dramas to the point where the reading of no cardiac electrical activity nicknamed flatline is often used as a symbol of death or at least extreme medical peril. This is technically known as asystole.