The time and intervalA period measured on rhythm strip paper that measures a wave and a segment; the distance measured is equal to time taken as an ECG is voltage over time; a PR interval for example is measured from the beginning of... measured from the beginning of the 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... 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 P wave to the start of the QRS complexThe electrical representation of ventricular depolarization; the atrial repolarization is also a part of the QRS. ECG interpretation relies heavily on the QRS complex. The QRS complex represents the depolarization of the ventricles. The repolarization of the atria is also.... While it might appear obvious that this is indeed a PQ interval, a Q waveA Q wave is the first negative deflection of the QRS complex that is not preceded by a R wave. A normal Q wave is narrow and small in amplitude. Note that a wide and/or deep Q wave may signify... is not always present on an ECGElectrocardiogram; also called an EKG; a representation of electrical voltage measured across the chest over a period of time. 1. Six Second ECG Guidebook (2012), T Barill, p. 196 tracing. For consistency, the term PR interval has been adopted whether a Q wave exists or not.
The PR interval can provide clues to both the location of the originating impulse and the integrity of the conduction pathways of the heart. A PR interval longer than normal (greater then 0.2 seconds) suggests that conduction is abnormally slow through 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.... This phenomenon is called first degree AV blockThe PR interval is the time from the beginning of the atrial wave to the beginning of myocardial depolarization of the ventricles. Normally this takes 0.12 - 0.20 seconds. When the time taken is over 0.20 seconds, this is called.... A PR interval 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 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...) 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 junction – is bypassed and thus shortened.
The PR interval covers the time taken for the impulse to travel 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... through the atria and the AV junction through to the Purkinje networkA matrix of fibres located throughout the myocardium that connects the impulse from the bundle branches to the myocardial tissue. The bundle branches and the Purkinje network facilitate rapid depolarization throughout the ventricles. The Purkinje network also creates a typical.... Most of the PR interval is taken by the slow conducting AV junction. Changes to the PR interval often points to the AV junction. A normal PR interval is 0.12-0.20 seconds, which is the equivalent to 3-5 small squares (3-5 mm) on ECG paperAn ECG is a graphical display of electrical energy generated by the heart over time. ECG graph paper records this cardiac electrical activity, printing at a rate of 25 mm/second. The paper graph is divided into small 1 mm squares....
If an ECG shows P wave, QRS complexA collection of waveforms (i.e. QRS complex and the ECG complex). 1. Six Second ECG Guidebook (2012), T Barill, p. 194 – P wave, QRS complex – P wave, QRS complex – 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..., ventricular depolarizationThe depolarization of the myocardium is represented on an ECG by a series of waveforms, one for atrial depolarization and soon after a larger waveform for ventricular depolarization. Normal ventricular depolarization begins with the septal fascicle of the left bundle... until the cows come home, a rather important relationship between the atria and the ventricle is revealed. If the P wave is consistently followed by a QRS complex across a consistent PR interval, this is strong evidence that the originating impulse is supraventricularLocated above the ventricle – includes the bundle of His, AV node, atria and the SA node. 1. Six Second ECG Guidebook (2012), T Barill, p. 206. A consistent PR interval is often sufficient to declare that this is a supraventricular rhythmIf the QRS is narrow, the rhythm originates from a supraventricular site. Otherwise, if the QRS is wide, chances are, the rhythm is a ventricular rhythm. Remember that the ECG is a two dimensional plotting of voltage (height or amplitude)....
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 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. 80-82, 112, 201