الفهرس 
Electrophysiology and Normal ECGOnly 14 pages are availabe for public view
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Abstract
The body acts as a giant conductor of electrical current. Electrical activity that originates in the heart can be detected on the body’s surface through an electrocardiogram (ECG). An ECG is a series of waves and deflections recording the heart’s electrical activity.
Although most of the ECG abnormalities detected in patients in the emergency department or ICU are caused by primary cardiac diseases, ECG changes do not invariably imply a cardiac abnormality. A thorough knowledge of the ECG manifestations of noncardiac conditions, commonly seen in critical care settings, may result in rapid diagnosis and correct treatment of potentially life-threatening disorders. Misinterpretation of the ECG may even expose the patient to wrong therapeutic options, with serious risks.
The specific electrocardiographic (ECG) changes caused by electrolyte imbalance are attributed to the effect of the altered concentration of ions on the transmembrane potentials of cardiac cells. For example, the terms hyperkalemia and hypokalemia are commonly used for alterations in serum levels of potassium. Since abnormalities in either of these conditions may be life threatening, an understanding of the ECG changes they produce is important.
QT prolongation has attracted a great deal of attention because of its apparent association with life threatening cardiac arrhythmias such as Torsades de Pointes (TdP). This arrhythmia refers to a rapid and irregular polymorphic ventricular tachycardia.
Both cardiac drugs and other medications can cause ECG changes. Many antiarrhythmic drugs display a proarrhythmic effect. In recent years, reports of TdP and syncope or cardiac arrest during therapy with antihistamines, antibiotics, GI prokinetic drugs, and others have drawn attention to the potential proarrhythmic effects of noncardiovascular drugs.
Cardiac toxicity is a common finding in patients who have been poisoned with a wide variety of chemical agents. Poisons that result in ECG changes include carbon monoxide (CO), cyanide, organophosphates, arsenic, or even specified herbal therapies.
The ECG may also play a role in diagnosis and management for many various noncardiac conditions such as pulmonary embolism, CNS diseases, hypothermia, esophageal disorders, endocrine abnormalities and electrical injury; however, most of this disorders do not produce specific changes on the ECG.