Review for Exam 2 Eall 2017 Exam is on junctional, ventriclar arrhythmias and AV

Question

Review for Exam 2 Eall 2017 Exam is on junctional, ventriclar arrhythmias and AV blocks Know the criteria for junctional arrhythmias (Grid, Powerpoint, and Aeblert) Be able to identify PJC's, junctional rhythm, accelerated junctional rhythm, junctional tachycardia and junctional escape beats. Know the criteria for ventricular arrhythmias (Grid, Powerpoint, and Aeblert) Be able to identify idioventriculac rhythm, accelerated idivnculac rhythm, ventricular tachycardia, ventricular fibrillation, asystole, and pulseless electrical activity Know which type of pause follows a PAC, PJC, and PVC (non-compensatory, compensatory) Know the criteria for AV blocks (Grid, Powerpoint, and Aehlert) Be able to identify first degree block, second degree blocks, and third degree block Know the definitions of terms for arrhythmias that are controlled, uncontrolled, sustained, non- sustained. Know descriptions of patterns in arrhythmias (couplet, run) and unifocal, multifocal, naming them appropriately

Explanation / Answer

Junctional rhythm: An abnormal heart rhythm resulting from impulses coming from a locus of tissue in the area of the atrioventricular node.

Normal condition: The electrical activity of sinus rhythm originates in the sinoatrial node and depolarizes the atria. Current then passes from the atria through the atrioventricular node and into the bundle of His, from which it travels along Purkinje fibers to reach and depolarize the ventricles. This sinus rhythm is important because it ensures that the heart's atria reliably contract before the ventricles.

Junctional rhythm: The sinoatrial node does not control the heart's rhythm – this can happen in the case of a block in conduction somewhere along the pathway described above. When this happens, the heart's atrioventricular node takes over as the pacemaker.In the case of a junctional rhythm, the atria will actually still contract before the ventricles; however, this does not happen by the normal pathway of activation and instead is due to a backwards or retrograde conduction (conduction comes from the AV node into and through the atria). Junctional rhythm can be diagnosed by looking at an ECG: it usually presents without a P wave or with an inverted P wave. Retrograde P waves refers to the depolarization from the AV node back towards the SA node.

Ventricular arrhythmias: Abnormal heart rhythms that originate in the bottom chambers of the heart called the ventricles. These rhythms can occur as a result of damage to the heart muscle from a heart attack or cardiomyopathy – or can occur in patients with hearts that seem structurally normal.

AV blocks:

Atrioventricular (AV) heart block describes impairment of conduction from the atria to the ventricles via the AV junction. This impairment occurs when the atrial impulse is either delayed or does not conduct to the ventricles. The sites of block include the AV node, the bundle of His, and the bundle branches.

The three commonly described types of AV block are 1st degree, 2nd degree and 3rd degree AV block. Second degree block is additionally divided into Mobitz type I and type II AV block. Type I is also known as Wenckebach.

·         First degree AV block: It is not a true block but instead is just a delay in conduction of the atrial impulse, resulting in an increased PR interval of greater than 200 msec.

·         Type I second degree AV block: Involves progressive PR lengthening until the QRS “drops out,” indicating the previous P wave was not conducted to the ventricles. This is typically a nodal block.

·         Type II second degree AV block: occurs in the setting of a constant PR interval with sudden nonconduction of a P wave. Type II second degree AV block may present as a single nonconducted P wave or a repetitive pattern of nonconduction (2:1, 3:1, etc.). This block is commonly infranodal.

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