Electrocardiography

Electrocardiography is one of the most basic noninvasive diagnostic methods in medicine. Graphic record of the electrocardiography is called electrocardiogram (ECG, EKG). It is based on recording of electric potential generated by heart on body surface. This methode is used in diagnostic of heart disease.

Indications
ECG is indicated if there is suspicion on:
 * heat disease: heart attack, arrhythmias, conduction disturbances, myocardial ischemia;
 * metabolic disease: hypocalcemia or hypercalcemia, hypokalemia or hyperkalemia;
 * endocrine disease: diseases of the thyroid gland (hypothyroidism and hyperthyroidism).

Principle
Everything is based on heart depolarization and repolarization. These processes can be presented by vectors of electrical potentials. ECG is recording of summation of electrical potential vectors from multiple myocardial fibers, not only from cardiac conduction system. Every myocardial fiber can generate electrical potential. These electrical potentials are conducted by body fluids (which are very good conductors) to the body surface, where are recorded.

Related articles

 * Action Potential and Autorhythmicity
 * ECG abnormalities