A wave generated from the 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... of the atriaRight and left atria (1/3 volume and muscle mass of the ventricles) pump blood to the ventricles. Chambers and Layers of the Heart 1. Six Second ECG Guidebook (2012), T Barill, p. 190; the P wave is upright when originating from the SA nodeThe SA node, usually the dominant pacemaker, is located in the right atrium at the opening of the superior vena cava. The SA (sinoatrial) node is a clump of hundreds of specialized cardiac cells that have the ability to self-initiate....
The P wave represents the depolarization of the right and left atria. The P wave begins with the first deviation from baselineThe baseline or isoelectric line is a reference point for the waves, intervals and segments. While the PR segment is often used as the baseline, the TP segment - between the end of the T wave and the beginning of... and finishes when the wave meets the baseline once again. While the P wave is an electrical representation and not mechanical, a P wave strongly suggests that the atria have followed through with a contraction.
In Figure 4.12, several ECG componentsAn ECG is composed of a series of waves and lines usually ordered into some repeatable pattern. The waves and lines are displayed on either a two dimensional screen or on ECG paper. The height of the tracing represents millivolts... are labelled. Note that a waveformA wave of an ECG. 1. Six Second ECG Guidebook (2012), T Barill, p. 209 is produced when the electrical potential of cardiac cell membranes change. During atrial depolarization, the atrial cell membranes quickly become more positive producing a P wave. The baseline or isoelectric lineAlso called the baseline, the straight line that is present when no electrical activity is present. The baseline or isoelectric line is a reference point for the waves, intervals and segments.While the PR segment is often used as the baseline,... represents nothing more than an absence of voltage change to the cardiac cells.
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. 81, 103, 110-112, 201