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Harrison's Principles of Internal Medicine, 18e
| Part 10. Disorders of the Cardiovascular System > Section 2. Diagnosis of Cardiovascular Disorders > |
Chapter 228. Electrocardiography
Sections: Electrocardiography: Introduction, Genesis of the Normal ECG, Major ECG Abnormalities, Further Readings.
Topics Discussed: cardiovascular testing; electrocardiogram; electrocardiography and ecg abnormalities.
Excerpt:"An electrocardiogram (ECG or EKG) is a graphic recording of electric potentials generated by the heart. The signals are detected by means of metal electrodes attached to the extremities and chest wall and then are amplified and recorded by the electrocardiograph. ECG leads actually display the instantaneous differences in potential between the electrodes.(See also Chaps.232 and 233) Depolarization of the heart is the initiating event for cardiac contraction. The electric currents that spread through the heart are produced by three components: cardiac pacemaker cells, specialized conduction tissue, and the heart muscle itself. The ECG, however, records only the depolarization (stimulation) and repolarization (recovery) potentials generated by the atrial and ventricular myocardium...."
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