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Unformatted text preview: 1 The Electrocardiogram Bekah Gensure firstname.lastname@example.org M.D. / Ph.D. Candidate ECG Lecture Overview Fundamentals of heart electrical activity History of electrocardiogram Cardiac anatomy Cardiac physiology (action potentials) ECG timing and amplitudes Clinical correlations Summary The Heart Is a pump Has electrical activity (action potentials) Generates electrical current that can be measured on the skin surface E LECTRO C ARDIO G RAM (ECG / EKG) 2 Cells of the heart Cardiac myocytes (muscle cells) Contractile machinery Pacemaker cells Electrical power source of heart Spontaneously depolarize Electrical conducting cells Rapid conduction system (hard wiring) Myocyte AP Pacemaker AP Currents and Voltages At rest, V m is constant No current flowing Inside of cell is at constant potential Outside of cell is at constant potential + + + + + + + + + + + + A piece of cardiac muscle outside inside 0 mV + Depolarization During AP upstroke, V m is NOT constant Current IS flowing Inside of cell is NOT at constant potential Outside of cell is NOT at constant potential + + + + + + + + + + + + + A piece of cardiac muscle outside inside Some positive potential + current AP An action potential propagating toward the positive ECG lead produces a positive signal 3...
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This document was uploaded on 02/09/2012.
- Spring '09