A PR intervalThe time and interval measured from the beginning of the P wave to the beginning of the QRS; should be called the PQ interval; normal PR interval is 0.12-0.20 seconds. The PR interval is measured from the start of the... shorter than normal (less than 0.12 seconds) occurs commonly with junctional rhythmsA cardiac rhythm that occurs as a backup pacemaker when the sinus node fails to initiate an impulse; the junction typically fires at 40-60/minute; the P wave is either absent or inverted. A cardiac rhythm is usually named first by... (the impulse begins somewhere in the AV junctionConducts the impulse through the fibrous plate that separates the atria and the ventricles; consists of the AV node and the bundle of His; functions also to slow the conduction speed to allow for atrial conduction prior to ventricular conduction...) because part of the conduction pathway – 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 and part of the AV junctionConnects the atria to the ventricle and slows the impulse conduction speed sufficiently to allow for atrial kick; the junction consists of the AV node and the bundle of His; the junction is a supraventricular structure. 1. Six Second ECG... – is bypassed and thus shortened.
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 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..., the atrial cell membranes quickly become more positive producing a P waveA wave generated from the depolarization of the atria; the P wave is upright when originating from the SA node. The P wave represents the depolarization of the right and left atria. The P wave begins with the first deviation.... The 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... 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. 82