8 Introducing the Atrial Rhythms 1

Introducing the Sinus Rhythms Objectives Discuss the origin of the atrial rhythms Recall the components of the electrical conduction system of the heart Identify a wandering atrial pacemaker rhythm, including EKG characteristics Describe a premature atrial contraction, including EKG characteristics Identify atrial flutter rhythm, including EKG characteristics

Introducing the Sinus Rhythms Objectives (continued) Describe atrial fibrillation rhythm, including EKG characteristics Describe supraventricular tachycardia, including EKG characteristics Discuss clinical significance of atrial rhythms Describe EKG characteristics of Wolff-Parkinson-White syndrome

Origin of the Atrial Rhythms The rhythms are classified according to the heart structure in which they begin, or their site of origin Sinoatrial (SA) node fails to generate an impulse, atrial tissues, or internodal pathways may initiate an impulse

Origin of the Atrial Rhythms These are Atrial Dysrhythmias Rhythms not considered life-threatening or lethal; They must however, provide continuous assessment

Components of Electrical Conduction System of the Heart Electrical impulse originates in SA node Travels through atria via internodal pathways AV node, brief pause, bundle of His Right and left bundle branches Purkinje fibers into the ventricular musculature

Electrical Conduction System of the Heart

Pacemaker Sites

Wandering Atrial Pacemaker Rhythm They occur when pacemaker sites wander, or travel, from SA node to other pacemaker sites in atria, internodal pathways, or AV Node SA node remains basic pacemaker

Wandering Atrial Pacemaker Rhythm Observation of at least three different P waves required Size and shape of P waves vary according to site of origin The P waves may appear upright, inverted, or absent waveforms

Wandering Atrial Pacemaker Rhythm The absence of P wave may indicate P wave buried in QRS complex PR interval may be regular, vary based on point of origin Produces no symptoms and only recognized by EKG observation

Wandering Atrial Pacemaker

Wandering Atrial Pacemaker Rhythm

Multifocal Atrial Tachycardia (MAT) A variant of wandering atrial pacemaker Occurs when the rate reaches 100 bpm or greater May be confused with atrial fibrillation Observed in patients with advanced chronic obstructive pulmonary disease, digoxin toxicity, and electrolyte imbalances.

Multifocal Atrial Tachycardia (MAT)

Premature Atrial Contractions (Complexes) or PACs A single electrical impulse that originates outside the SA node in the atria Can occur in the atria, AV junction, or in the ventricles The premature beat is a complex that arises earlier than next expected beat

Premature Atrial Contractions (Complexes) or PACs The word contraction commonly used to describe premature beats All complexes represent only electrical activity of the heart Complexes do not show mechanical activity. Should use complexes rather then contraction

Premature Atrial Complexes An incomplete, or noncompensatory, pause often follows a PAC Looks like normal complexes of underlying rhythm Underlying rhythm is interrupted due to PAC After noncompensatory pause, underlying rhythm of heart returns, and continues until next PAC occurs

Premature Atrial Complexes

Figure 8-2 Premature Atrial Complexes

Premature Atrial Complexes Two sequential PACs Occur in pairs Atrial bigeminy Every other beat PAC Atrial trigeminy Every third beat PAC

Premature Atrial Complexes Remember Premature atrial complexes look very much like the normal complexes of the underlying rhythm

Premature Atrial Complexes Causes include Use of stimulants (caffeine, alcohol) hypoxia, increased sympathetic tone, imbalances of electrolytes, digitalis toxicity When any premature beat occurs more than six times per minute it is termed “frequent”

Reentry Dysrhythmias The reactivation of myocardial tissue for a second or subsequent time by the same impulse Short circuit of electrical conduction system Develops when course of electrical impulse is delayed or blocked

Reentry Dysrhythmias Due to this delay, electrical impulse allowed to travel in only one direction The impulse moves in cycle throughout heart tissue A series of fast depolarizations ensues

Reentry Dysrhythmias

Reentry Dysrhythmias Causes of reentry Specific rhythms include Due to conduction delays or blocks include hyperkalemia, myocardial ischemia, and certain antidysrhythmic medications Specific rhythms include Atrial flutter, atrial fibrillation, premature atrial complexes, and paroxysmal supraventricular tachycardia

Atrial Flutter Rhythm Presence of regular atrial activity with a picket fence, or sawtooth pattern Single irritable site in atria initiates many electrical impulses at a rapid rate Normal P wave not produced Electrical impulses conducted throughout atria at fast rate

Atrial Flutter Rhythm Rather than the presence of normally appearing P waves, flutter (or sawtooth) waves, also known as F waves, are patterned AV node becomes “gate keeper” to ventricles Based on number of impulses AV node accepts, ventricular response is established

Atrial Flutter Rhythm Conduction ratio 2:1 Conduction ratio 4:1 Two atrial contractions for each ventricular contraction Conduction ratio 4:1 Four atrial contractions for each ventricular contraction An atrial rate of 300 bpm will parallel a ventricular rate of 75 bpm

Atrial Flutter Rhythm Atrial flutter with a slow ventricular response Ventricular rate of less than 60 bpm Atrial flutter with a rapid ventricular response Ventricular rate of 100-150 bpm

Atrial Flutter

Atrial Flutter