1. 8
Introducing the Atrial Rhythms 1

2. 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

3. 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

4. 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

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

6. 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

7. Electrical Conduction System of the Heart

8. Pacemaker Sites

9. 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

10. 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

11. 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

12. Wandering Atrial Pacemaker

13. Wandering Atrial Pacemaker Rhythm

14. 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.

15. Multifocal Atrial Tachycardia (MAT)

16. 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

17. 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

18. 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

19. Premature Atrial Complexes

20. Figure 8-2 Premature Atrial Complexes

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

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

23. 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”

24. 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

25. 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

26. Reentry Dysrhythmias

27. 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

28. 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

29. 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

30. 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

31. 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 bpm

32. Atrial Flutter

33. Atrial Flutter