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© Dirk Biddle
An electrocardiogram (ECG or EKG) is used to measure the rate and regularity of heartbeats as well as the size and position of the chambers, the presence of any damage to the heart and the effects of drugs or devices used to regulate the heart (such as a pacemaker). With each beat, an electrical impulse (or “wave”) travels through the heart. This impulse causes the heart muscle to contract and pump blood from the heart.
To administer the test, the patient is asked to lie down, and the areas to which the electrodes are to be fastened are cleaned and shaved if necessary. Several electrodes are secured to the patient's skin and connected to a screen. The patient is asked to lie still and hold his or her breath briefly.
An ECG provides two major kinds of information. First, by measuring time intervals on the ECG, a doctor can determine how long the electrical wave takes to pass through the heart. Finding out how long a wave takes to travel from one part of the heart to the next shows if the electrical activity is normal or slow, fast or irregular. Second, by measuring the amount of electrical activity passing through the heart muscle, a paediatric cardiologist may be able to find out if parts of the heart are too large or are overworked.
The test is sometimes undertaken on patients walking on an indoor running machine, or in some other way made to undergo light physical exertion. This is done to monitor changes in the heart's activity and is sometimes called a “stress test”.
Abnormal ECG results may indicate Myocardial (cardiac muscle) defect
Enlargement of the heart, Congenital defects, Heart valve disease, Arrhythmias (abnormal rhythms), Tachycardia (heart rate too fast) or bradycardia (too slow), Ectopic heartbeat, Coronary artery disease, Inflammation of the heart (myocarditis), Changes in the amount of electrolytes (chemicals in the blood), Past heart attack and Present or impending heart attack. Additional conditions under which the test may be performed include Alcoholic cardiomyopathy, Anorexia nervosa, Aortic dissection, Aortic insufficiency, Aortic stenosis, Atrial fibrillation/flutter, Atrial myxoma; left, Atrial myxoma; right, Atrial septal defect, Cardiac tamponade, Coarctation of the aorta, Complicated alcohol abstinence (delirium tremens), Coronary artery spasm, Digitalis toxicity, Dilated cardiomyopathy, erythematosus, Familial periodic paralysis, Guillain-Barre, Heart failure, Hyperkalaemia, Hypertensive heart disease, Hypertrophic cardiomyopathy, Hypoparathyroidism, Idiopathic cardiomyopathy, Infective endocarditis, Insomnia, Ischemic cardiomyopathy, Left-sided heart failure, Lyme disease, Mitral regurgitation; acute, Mitral regurgitation; chronic, Mitral stenosis, Mitral valve prolapse, Multifocal atrial tachycardia, Narcolepsy, Obstructive sleep apnoea, Paroxysmal supraventricular tachycardia, Patent ductus arteriosus, Pericarditis, Bacterial pericarditis, Constrictive pericarditis, Post-MI pericarditis, Peripartum cardiomyopathy, Primary amyloid, Primary hyperaldosteronism, Primary hyperparathyroidism, Primary pulmonary hypertension, Pulmonary embolus, Pulmonary valve stenosis, Restrictive cardiomyopathy, Right-sided heart failure, Sick sinus syndrome, Stable angina, Stroke, Systemic lupus erythematosus, Tetralogy of Fallot, Thyrotoxic periodic paralysis, Transient ischemic attack (TIA), Transposition of the great vessels, Tricuspid regurgitation, Type 2 diabetes, Unstable angina, Ventricular septal defect, Ventricular tachycardia and Wolff-Parkinson-White syndrome (1).
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1)http://www.nlm.nih.gov/medlineplus/ency/article/003868.htm
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