A cardiac rhythmOften refers to a discernible pattern in time or distance between QRS complexes and/or P waves. that occurs when the 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... (or possibly bilateral bundle branchesThe bundle of His terminates in the right and left bundle branches, insulated rapidly conducting electrical pathways that connect with the Purkinje network and thus begin depolarizing waves across the ventricles; the left bundle branch splits into three smaller branches...) does not conduct the impulse from 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 to the ventriclesThe larger chambers of the heart (3 times the volume and muscle thickness than the atria), responsible for the pumping of blood to the lungs and the rest of the body.; a pacemakerAn electronic pulse generator that stimulates depolarization of the atria and/or the ventricles. 1. Six Second ECG Guidebook (2012), T Barill, p. 201 below the block must then begin firing to sustain cardiac outputWhat is it? Why is it Vital? The amount of blood pumped out of the ventricle in a minute (most often refers to the blood pumped by the left ventricle) What is cardiac output? Simply, cardiac output is the amount...; thus, the atria and the ventricle fire independently.
Atrioventricular blocksAtrioventricular blocks (AV blocks) result from a conduction disturbance at or just below the AV junction. The 3rd step of the 3 step process prompts us to check the P waves and the PR interval. Abnormal PR intervals and lonely... (AV blocks) result from a conduction disturbance at or just below 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.... The 3rd step of the 3 step process prompts us to check the P wavesA 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... and PatternPattern refers to the repeating components of an ECG rhythm in a predicative order. An ECG rhythm that is initiated by one of several intrinsic pacemaker sites of a heart will often generate a regular, even rhythm pattern. This can... with particular attention to the PR 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.... Abnormal PR intervalsThe 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... and lonely ‘P’ waves define the type of AV block.
From a clinical perspective, the severity of a block is similar to the severity of burns. The higher the degree of burn the more aggressive the treatment. Similar escalation in treatment is required for higher levels of AV blocks. The affects of 2nd degree type II and 3rd degree AV blocks on cardiac output can be much more significant than the affects of 2nd degree type I and 1st degree AV blocks.
Third degree AV block (complete heart blockAlso known as complete heart block, the supraventricular impulse is blocked at the junction or high in the bundle branches; as a result, the myocardium above the block depolarizes independently of the myocardium below the block; characteristics of this rhythm...) can occur at any part of the junction or further down in the bundle branches. Instances of third degree heart block occurring high in the AV nodeIs located in the inferior aspect of the right atria; functions to slow the conduction speed to allow for atrial conduction prior to ventricular conduction (atrial kick); also serves as a pacemaker if the SA node fails to fire. The... often have a narrow 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... (pacing below the block is provided by the bundle of HisPart of the AV junction, the bundle of His conducts the impulse through the fibrous plate that separates the atria and the ventricle; the bundle of His is also a pacemaker, firing at 40-60/minute. The bundle of His serves as... producing a narrow QRS complexA collection of waveforms (i.e. QRS complex and the ECG complex). 1. Six Second ECG Guidebook (2012), T Barill, p. 194). Third degree AV block at the bundle of His or the bundle branches, a wide QRS often results (pacing below the block is provided by the ventricles).
Note that third degree AV block with narrow QRS complexes may respond favorably to the use of a vagolytic medication such as Atropine. A third degree AV block with wide QRS complexes, though, is rarely responsive to Atropine. The Vagus nerve lands on the SA and AV node only. For AV blocks that are located below the junction (third degree and second degree type II), Atropine is not the treatment of choice.
With complete heart block, the atria and the ventricles are electrically severed. This is one form of atrioventricular dissociation. Because the atria and the ventricles are beating to two separate drummers, the defining characteristics of third degree AV block are: 1) regular ventricular (and atrial) rhythms; and 2) chaotic PR interval. This dysrhythmiaUsed interchangeably with arrhythmia, refers to any abnormal rhythm – not normal sinus rhythm or sinus tachycardia. 1. Six Second ECG Guidebook (2012), T Barill, p. 196 often requires urgent attention (dependent on ventricular rateHeart Rate; calculated by counting the number of QRS complexes in six seconds and multiplying by 10; rate is also determined by measuring the number of large squares between two R waves; i.e. –1 large square = heart rate of 300/minute.) with treatments that include transcutaneous pacing.”
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. 125, 128, 207