1. Fast & Easy ECGs – A Self-Paced Learning Program9
Atrial Dysrhythmias
Fast & Easy ECGs – A Self-Paced Learning Program Q I A

2. Atrial Dysrhythmias
Originate in the atrial tissue or in the internodal pathways
Question to ask “What is the normal pacemaker site which initiates the heartbeat?” Q

3. Atrial Dysrhythmias Believed to be caused by three mechanisms:
Automaticity
Triggered activity
Reentry
Instructional point:
Increased automaticity and triggered activity are disorders of impulse formation. Reentry is a problem with impulse conduction. In increased automaticity, the atrial cells spontaneously depolarize and initiate impulses before the SA node has a chance to generate a normal impulse. Injured cells sometimes only partially repolarize. Partial repolarization can lead to a repetitive ectopic firing called triggered activity. Reentry occurs when an impulse is delayed along a slow conduction pathway and the impulse is able to remain active long enough to produce another impulse in the atria while the ventricles are repolarizing. I

4. Atrial Dysrhythmias
Can affect ventricular filling time and diminish the strength of the atrial contraction
This can lead to decreased cardiac output and ultimately decreased tissue perfusion
Instructional point:
The atrial contraction is called the atrial “kick” and normally supplies the ventricles with about 30% of their blood. I

5. Atrial Dysrhythmias Key characteristics include:
P’ waves (if present) that differ in appearance from normal sinus P waves
Abnormal, shortened, or prolonged P’R intervals
QRS complexes that appear narrow and normal
Instructional point:
With atrial dysrhythmias the QRS complexes may be wider than normal if there is intraventricular conduction defect, aberrancy or preexcitation. I

6. Wandering Atrial Pacemaker
Pacemaker site shifts between the SA node, atria and/or AV junction
This produces its most characteristic feature – P’ waves that change in appearance
Instructional point:
With wandering atrial pacemaker the regularity of the rhythm also varies slightly. I

7. Wandering Atrial Pacemaker

8. Wandering Atrial Pacemaker
Generally caused by the inhibitory vagal effect of respiration on the SA node and AV junction
Normal finding in children, older adults, and well-conditioned athletes
Not usually of any clinical significance
May be related to some types of organic heart disease and drug toxicity, specifically digitalis
Instructional point:
At least three different P wave configurations (seen in the same lead) are needed to diagnose a dysrhythmia as wandering atrial pacemaker. I

9. Premature Atrial Complexes (PACs)
Early ectopic beats that originate outside the SA node

10. Premature Atrial Complexes (PACs)
Produce an irregularity in the rhythm
P’-P and R’-R intervals are shorter than the P-P and R-R intervals of underlying rhythm
Have P’ waves that are upright (in lead II) preceding each QRS complex but have a different morphology (appearance) than the P waves of underlying rhythm
Followed by a noncompensatory pause

11. Premature Atrial Complexes

12. Noncompensatory Pause
A pause where there are less than two full R-R intervals between the R wave of the normal beat which precedes the PAC and the R wave of the first normal beat which follows it.

13. Noncompensatory Pause
Play the noncompensatory pause video clip from the student DVD. A

14. Premature Atrial Complexes
Instructional point:
In some cases there is no apparent cause. I

15. Premature Atrial Complexes
Isolated PACs seen in patients with healthy hearts are considered insignificant
Asymptomatic patients usually only require observation
Instructional points:
PACs commonly cause no symptoms and can go unrecognized for years.
The patient may perceive PACs as “palpitations” or skipped beats. I

16. Premature Atrial Complexes
May predispose patient with heart disease to more serious atrial dysrhythmias:
atrial tachycardia
atrial flutter
atrial fibrillation
Can serve as an early indicator of an electrolyte imbalance or congestive heart failure in patients experiencing an acute myocardial infarction

17. Premature Atrial Complexes
Bigeminal
Trigeminal
Ask question – “What do bigeminal, trigeminal and quadrigeminal mean?”
Quadrigeminal Q

18. Premature Atrial Complexes
May have wide QRS complexes when seen with abnormal ventricular conduction
For this reason they can be confused with PVCs
Instructional point:
To tell the difference between PACs and PVCs look for either a compensatory or non-compensatory pause and the presence or absence of P waves. I

19. Atrial Tachycardia
Rapid dysrhythmia (rate of 150 to 250 BPM) that arises from the atria.
Rate is so fast it overrides the SA node
Instructional point:
When the onset of the atrial tachycardia is sudden (and typically witnessed) it is called paroxysmal. I

20. Atrial Tachycardia

21. Atrial Tachycardia

22. Atrial Tachycardia May occur in short bursts or may be sustained
Short bursts are well-tolerated in otherwise normally healthy people
With sustained rapid ventricular rates, ventricular filling may not be complete during diastole

23. Atrial Tachycardia
Can significantly compromise cardiac output in patients with underlying heart disease
Fast heart rates increase oxygen requirements
May increase myocardial ischemia and potentially lead to myocardial infarction
Instructional point:
Atrial tachycardia can cause vertigo (dizziness), lightheadedness, syncope, hypotension and congestive heart failure. I

24. Multifocal Atrial Tachycardia (MAT)
Pathological condition that presents with changing P wave morphology and heart rates of 120 to 150 BPM
Instructional point:
Multifocal atrial tachycardia has the same characteristics (changing P wave morphology) as wandering atrial pacemaker. I

25. Supraventricular Tachycardia (SVT)
Arises from above the ventricles but cannot be definitively identified as atrial or junctional tachycardia because the P’ waves cannot be seen sufficiently
Includes paroxysmal supraventricular tachycardia, (PSVT), nonparoxysmal atrial tachycardia, multifocal atrial tachycardia

26. Atrial Flutter
Rapid depolarization of a single focus in the atria at a rate of 250 to 350 BPM

27. Atrial Flutter
Produces atrial waveforms that have a characteristic saw-tooth appearance
Called flutter waves (F waves)

28. Atrial Flutter

29. Atrial Flutter Often well-tolerated
The number of impulses conducted through the AV node determines the ventricular rate (i.e. 3:1 conduction ratio)
Slower ventricular rates (< 40 BPM) or faster ventricular rates (> 150 BPM) can seriously compromise cardiac output
Instructional point:
Rapid ventricular rates can produce a loss of “atrial kick,” decreased ventricular filling time and decreased coronary artery perfusion. This can lead to angina, heart failure, pulmonary edema, hypotension and syncope. I

30. Atrial Fibrillation
Chaotic, asynchronous firing of multiple areas within the atria
Show animation: “Atrial fibrillation”
Instructional point:
it is believed that atrial fibrillation stems from the rapid firing of ectopic impulses (greater than 350 beats per minute) in circus reentry pathways. I A

31. Atrial Fibrillation
Totally irregular rhythm with no discernible P waves instead there is a chaotic baseline of fibrillatory waves (f waves) representing atrial activity

32. Atrial Fibrillation

33. Atrial Fibrillation
Leads to loss of atrial kick decreasing cardiac output by up to 25%
Patients may develop intra-atrial emboli as the atria are not contracting and blood stagnates in the atrial chambers forming a thrombus (clot)
Predisposes patient to systemic emboli (stroke)

34. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 375 BPM, Ventricular rate 100 BPM, regular rhythm, atrial waveforms have saw-tooth pattern F waves are present, , QRS (more accurately described as RS) complexes at 0.08 seconds, PRI immeasurable, QT immeasurable. Atrial flutter with a 4 to 1 conduction ratio. I

35. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate is greater than 350 BPM, Ventricular rate 100 BPM, totally irregular, P waves are indiscernible f waves are present, QRS (more accurately described as QS) complexes at 0.12 seconds, PRI is immeasurable, QT is immeasurable. Atrial fibrillation. I

36. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 65 BPM, Ventricular rate 65 BPM, occasionally irregular (due to the premature beat), normal and upright P waves in the underlying rhythm, P′ wave of premature beat differs from P waves of underlying rhythm, notched QRS complexes at 0.10 seconds,
PRI 0.16 seconds, QT 0.38 seconds. Normal sinus rhythm with a premature atrial complex (PAC)
(2nd beat). I

37. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 300 BPM, Ventricular rate 70 BPM, variably irregular rhythm, atrial waveforms have sawtooth pattern F waves are present, normal QRS complexes at 0.08 seconds, PRI immeasurable, QT immeasurable. Atrial flutter with a variable conduction ratio. I

38. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 80 BPM, Ventricular rate 80 BPM, regular rhythm, varying P waves, normal QRS complexes at 0.08 seconds, PRI varies, QT seconds, normal. Wandering atrial pacemaker. I

39. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 60 BPM, Ventricular rate 60 BPM, occasionally irregular (due to the premature beat), normal and upright P waves in the underlying rhythm, P′ wave of premature beat differs from P waves of underlying rhythm, normal QRS complexes at 0.10 seconds, PRI 0.16 seconds, QT 0.48 seconds. Normal sinus rhythm with a premature atrial complex (PAC) (2nd beat). I

40. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 214 BPM, Ventricular rate 214 BPM, regular rhythm, P is absent, normal QRS complexes at 0.08 seconds, PRI is immeasurable, QT seconds. Supraventricular tachycardia. I

41. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 58 BPM, Ventricular rate 58 BPM, frequently irregular (for what you see on the tracing), normal and upright P waves (P′ waves of premature beat differ from the P waves of the underlying rhythm, and one is buried in T wave of the preceding beat), QRS (more accurately described as RS) complexes at 0.10 seconds, PRI 0.24 seconds, QT 0.48 seconds. Sinus bradycardia with 2 premature atrial complexes (PACs) (4th and 6th beats). There is also a 1st-degree AV heart block. I

42. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 120 BPM, Ventricular rate 120 BPM, irregular, varying P waves, normal QRS complexes at 0.06 seconds, PRI immeasurable, QT seconds. Multifocal atrial tachycardia. I

43. Practice Makes Perfect
Determine the type of dysrhythmia
Answer: Atrial rate 60 BPM at first then immeasurable, Ventricular rate 60 BPM accelerating to 167 BPM, regular then sudden acceleration in heart rate, normal P waves then absent, normal QRS complexes at 0.10 seconds, PRI seconds, QT seconds. Paroxysmal supraventricular tachycardia. I

44. Summary
Atrial dysrhythmias originate outside the SA node in the atrial tissue or in the internodal pathways.
Three mechanisms responsible for atrial dysrhythmias are increased automaticity, triggered activity and reentry.
Key characteristics for atrial dysrhythmias:
P’ waves (if present) that differ from sinus P waves.
Abnormal, shortened, or prolonged P’R intervals.
QRS complexes that appear narrow and normal (unless there is an intraventricular conduction defect, aberrancy or preexcitation).

45. Summary
With wandering atrial pacemaker the pacemaker site shifts between the SA node, atria and/or AV junction.
Produces its most characteristic feature, P’ waves that change in appearance.
Premature atrial complexes (PACs) are early ectopic beats that originate outside the SA node.
Produce an irregularity in the rhythm.
P’ waves should be an upright (in lead II) preceding the QRS complex but has a different morphology than the P waves in the underlying rhythm.

46. Summary
Atrial tachycardia is a rapid dysrhythmia (rate of 150 to 250 beats per minute) that arises from the atria.
Multifocal atrial tachycardia (MAT) is a pathological condition that presents with the same characteristics as wandering atrial pacemaker but has heart rates of 120 to 150 beats per minute.
Supraventricular tachycardia arises from above the ventricles but cannot be definitively identified as atrial or junctional because the P’ waves cannot be seen with any real degree of certainty.

47. Summary
Atrial flutter is a rapid depolarization of a single focus in the atria at a rate of 250 to 350 beats per minute.
Produces atrial waveforms that have a characteristic saw-tooth or picket fence appearance.
Atrial fibrillation occurs when there is chaotic, asynchronous firing of multiple areas within atria at a rate greater than 350 beats per minute.
Produces a totally irregular rhythm with no discernible P waves.