In phase 3 of the action potentialThe electrical activities of a cell from depolarization to repolarization; 5 phases (0-4) take place largely involving the sodium, potassium and calcium ions. Action Potential and the ECG 1. Six Second ECG Guidebook (2012), T Barill, p. 189, once the cell repolarizes to threshold potentialThe electrical potential point across the cell membrane where the cell’s channels open to cause depolarization; for example, in the heart’s myocardial cells, the fast sodium channels open if the electrical potential across the cell’s membrane is –60 to –70... to –90 mVmilliVolt; the ECG is usually calibrated to display 1mV = 10mm of amplitude. 1. Six Second ECG Guidebook (2012), T Barill, p. 200, the cell’s ion channels are once again receptive to depolarizationThe rapid influx of positive ions (sodium and/or calcium) into a cell – depolarization is necessary for contraction to occur. A depolarizing wave moves through the myocardium on average along a trajectory or vector. A vector is a force moving...; this period is also called the supernormal period – minimal impulse energy is required to stimulate sufficient ion transfer to reach thresholdThe minimum level of electrical current necessary for an artificial pacemaker to stimulate depolarization of the heart. 1. Six Second ECG Guidebook (2012), T Barill, p. 207 potential once again and cause depolarization.
1. Six Second ECG GuidebookA Practice Guide to Basic and 12 Lead ECG Interpretation, written by Tracy Barill, 2012 Introduction The ability to correctly interpret an electrocardiogram (ECG), be it a simple six second strip or a 12 lead ECG, is a vital skill... (2012), T Barill, p. 204