The electrical potential point across the cell membrane where the cell’s channels open to cause 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...; 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 mVmilliVolt; the ECG is usually calibrated to display 1mV = 10mm of amplitude. 1. Six Second ECG Guidebook (2012), T Barill, p. 200 (note polarized state = -90 mV) – the fast sodium channels opening leads to depolarization; in the SA and AV nodes, the 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 is approximately –40 mV.
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. 207