Electrocardiogram (Ecg)
An electrocardiogram (ECG) is a graphic representation of electrical activity in the heart that conveys information related to cardiac rhythms and the pumping of blood through the chambers of the heart. Electrocardiograms are also termed EKGs. The electrical activity measured relates to changes in electrical potentials during the cardiac cycle.
ECG tracing can provide information related to heart ventricle size, position, and capacity to pump blood. This information is vital to clinicians attempting to assess damage to cardiac tissue and function. Variance in electrical conduction patterns can also provide information regarding conductive patterns in the heart and can be related to abnormalities in electrically conductive concentrations of salt and mineral ions.
The heart produces weak electrical currents that can be detected by electrodes that are attached by leads to strategic monitoring locations on the surface of the body. The ECG is a passive test and the electrodes are often cleaned and the area of attachment covered with a conductive gel to improve reception. In order to provide the graphical tracing caused by the movement of a stylus pen over specially lined moving paper, the current received from the heart is amplified thousands of times.
Normal tracings or waves are divided into components termed, in order that they occur, the P, Q, R, S, and T waves. The QRS waves are often described as the QRS complex. The P wave corresponds with the start of atrial contraction and the QRS complex corresponds to the initiation of ventricular contractions. The T wave corresponds to the refractory period and recovery period following ventricular contraction.
In the normal healthy individual, there are approximately 60-100 P waves (corresponding to heartbeats) per minute. Bradycardia describes a rate of less that 60 P waves per minute and tachycardia is a condition where there are in excess of 100 P waves per minute in a resting subject. When there is a great variability (usually greater than ten percent) in P waves from one tracing to the next--or within one tracing--this indicates an arrhythmia in sinus rhythm.
Careful measurement of the heights of waves and intervals between particular wave components can often yield important diagnostic insights into abnormal ventricular rhythms, ventricular hypertrophy, myocardial infarction, myocarditis, and other pathological conditions. For example, enlargements in the atrium (hypertrophy) or in abnormal atrial rhythm are often reflected in P wave abnormalities. Conduction abnormalities (e.g., bundle branch blocks) often result in abnormal QRS complex patterns.
Holter monitors are portable ECG units that can be used to monitor long-term cardiac function. The patient carries the portable unit during normal activities.
This is the complete article, containing 421 words
(approx. 1 page at 300 words per page).
