1. DIAGNOSIS OF CARDIAC RHYTHMS
Lecture #2

2. I. Common Terminology Supraventricular vs. Ventricular Rhythms
• The differential is made on the basis of QRS duration
• If the QRS complex is narrow (< 0.12 sec):
– The ventricular myocardium is depolarized rapidly
– The rhythm is supraventricular in origin
• If the QRS complex is wide (> 0.12 sec):
– There is a delay in the spread of the electrical activation throughout the ventricles
– The origin of the rhythm may be in the ventricle itself

3. Premature Atrial Contraction (PAC)
• P-waves differ from normal
• P-waves appear early
• P-waves are followed by a normal-appearing QRS complex

4. MECHANISM PVC PAC

5. Premature Ventricular Contraction (PVC)
• NO P-waves present
• QRS complex is wide
• Ventricular Tachycardia (VT)
 3 consecutive PVC’s, at a rate  100 bpm
(Non-sustained VT - <30 sec)

6. I. Common Terminology (cont’d)
Arrhythmia
• Generally referred to as any rhythm other than normal sinus rhythm
3 general mechanisms that can cause arrhythmias:
Disorders of impulse formation:
Altered Automaticity
Triggered activity
Disorders of impulse conduction:
Re-entry

7. Mechanism of Arrhythmias:
Re-entrant Tachycardia
• Rhythm is secondary to a “loop” in the electrical circuitry (the re-entry pathway) resulting in tachycardia
Requires:
Unidirectional block (with recovery)
Slowed conduction through loop
• It may occur within the SA node, the AV node, or actually any ectopic foci in the atria or ventricles

8. MECHANISM: Re-entry Tachycardia

9. II. Diagnosing Cardiac Rhythms

10. A. Regular Supraventricular Rhythms

11. 1. Sinus Rhythm Normal Sinus Rhythm • Rate = 60 – 99 bpm
Sinus Bradycardia
• Rate  59 bpm
Sinus Tachycardia
• Rate  100 bpm

12. Sinus Rhythm Criteria:
1. Every QRS complex is preceded by a P-wave
2. P-waves appear normal, that is they are of sinus node origin:
A. Normal Morphology:
1. P-wave duration < 0.12 sec (< 3 boxes)
2. P-wave height < 2.5 mm (< 2.5 boxes)
B. Normal Axis:
1. P-waves is upright in leads II, III & aVF
2. P-waves is negative in lead aVR

13. 2. Paroxysmal Atrial Tachycardia (PAT)
Re-entrant tachycardia of supraventricular origin,
with a rate of 120 – 180 bpm (narrow complex)
P-waves may or may not be visible, depending on
the rate
If present, P-waves are usually regular and
inverted in lead II (they may be seen before,
during, or after the QRS complexes)
Usually idiopathic, but can also be seen in RHD,
COPD, MVP & digitalis toxicity

14. Paroxysmal Atrial Tachycardia

15. Paroxysmal Atrial Tachycardia

16. 3. Atrial Flutter A. Atrial rate ~ 250 – 350 bpm
B. Characterized by rapid, undulating“flutter-waves”:
1. Are best seen in leads aVF & V1
2. Have a longer duration & a greater amplitude than a normal P-wave
3. Have a saw-toothed appearance
C. There is always some degree of AV-block present (2:1, 3:1 or variable), which is why the atrial rate is always much greater than the ventricular rate

17. Atrial Flutter

18. Atrial Flutter (cont’d)
D. Carotid sinus massage – may exaggerate the
degree of AV-block & consequently slow down the QRS rate, to assist with the diagnosis
– This makes the flutter-waves more obvious!

19. 4. Junctional Rhythm
A. Impulses originate in the AV node with retrograde & antegrade conduction
B. QRS complexes are narrow & regular (this is still considered supraventricular!)
C. P-waves may be inverted in leads II, III & aVF & may occur before, during or after the QRS complexes
D. Junctional Rate = 40 – 55 bpm
E. This is usually an escape rhythm due to SA node dysfunction or digitalis toxicity!

20. Junctional Rhythm

21. Junctional Rhythm

22. AV-Nodal Re-entrant Tachycardia (AVNRT)
One of the most common causes of PSVT
P-waves may not be visible or may occur before, during or after the QRS complexes
Two pathways usually exist: slow (anterograde conduction) & fast (retrograde conduction)
D. More common in younger patients
E. Abrupt onset & offset

23. 6. AV Re-entrant Tachycardia (AVRT)
Another common cause of PSVT
Involves an “accessory pathway” (1:1500)
Usually utilizes the AV node as the anterograde & the accessory pathway as the retrograde limbs (Orthodromic AVRT) – accessory pathway may be “concealed”
In 10%, impulse travels retrograde across AVN, and anterograde over accessory pathway (Antidromic AVRT) – “pre-excitation” present

24. Pre-excitation
Pre-excitation: Impulse travels anterogradely th’ AV node + accessory pathway to ventricles
Examples include pre-excitation syndromes:
– Wolff–Parkinson–White syndrome
(pre-excitation + tacchycardia)
– Lown-Ganong-Levine (LGL) syndrome
– “Mahaim fiber tachycardias”

25. Wolff–Parkinson–White (WPW)
A. A supraventricular rhythm originating in the SA node with normal & regular P-waves
B. PR interval is abnormally short (< 0.12 sec)
C. QRS is wide with a “slurred upstroke” (AKA the delta-wave)
Delta-waves are due to the accessory conduction pathway (bundle of Kent) from the atria to the ventricles, that bypasses the AV node
Must manifest a tacchycardia at some point in time
E. Rx: Procainamide

26. Wolff–Parkinson–White

27. B. Irregular Supraventricular Rhythms

28. 1. Sinus Arrhythmia

29. 2. Wandering Atrial Pacemaker (WAP)
A. Pacing is from various foci within the atria
B. Heart rate <100 bpm
C. Contour or shape of P-waves vary from beat to
beat, in a single lead (always try to look at lead II!)
Associated with variations of P-R & P-P intervals,
resulting in an irregularly irregular rhythm
E. A common cause is rheumatic heart disease
So, Dx Criterion: Three consecutive P-waves with
different morphologies, on a single EKG lead,
with a heart rate <100 bpm

30. Wandering Atrial Pacemaker

31. Wandering Atrial Pacemaker

32. 3. Multifocal Atrial Tachycardia (MAT)
A. Multifocal Atrial Tachycardia (MAT) is similar to
wandering atrial pacemaker, except that the heart
rate 100 bpm
Again, you must have three different consecutive
P-wave morphologies on a given lead (again,
examine lead II!)
C. Irregularly irregular rhythm
D. Usually associated with end-stage COPD
E. Rx: Control the rate & treat the underlying problem

33. Multifocal Atrial Tachycardia

34. 4. Atrial Fibrillation
A. Random chaotic depolarizations of the atria at rates > 300 bpm
B. NO effective pumping of the atria takes place
– You loose ~25% of C.O., AKA the “atrial kick”
C. Irregularly irregular rhythm
May occur in any clinical situation which causes LAE, hyperthyroidism, or also with EtOH use (“holiday heart”)
E. Rx: Rate control & anti-coagulation

35. Atrial Fibrillation

36. Atrial Fibrillation
The ventricular rate can be either rapid or well-controlled, depending on the conduction through the AV node

37. C. Ventricular Rhythms …these are generally regular…!

38. 1. Idioventricular Rhythms
Rhythm originates in the ventricles, giving rise to wide & bizarre QRS complexes
B. The AV node & sometimes the SA node are not functioning normally!
D. The axis of T-waves is in the opposite direction of the QRS complexes
E. Rate = 20 – 40 bpm

39. Idioventricular Rhythms

40. Idioventricular Rhythm

41. 2. Accelerated Idioventricular Rhythm (AIVR)
A. Often develops following an acute MI!
B. Occurs in short bursts & lasts < 20 sec
C. Rate = 40 – 120 bpm

42. Accelerated Idioventricular Rhythm

44. 3. Ventricular Tachycardia (VT)
Once again, you see broad & bizarre QRS
complexes (> 0.12 sec)
B. Often with an abrupt onset
C. Rate  120 – 140 bpm
D. Can be monomorphic or polymorphic (Torsades)
Look for ventricular capture & fusion beats
– Capture beat: a normal atrial beat “breaks through”
BEFORE the ventricular beat has occurred
– Fusion beat: the atrial beat “breaks through” DURING
the ventricular beat

46. Monomorphic Ventricular Tachycardia

47. Polymorphic Ventricular Tachycardia (Torsades de Pointes)

48. Wide complex tacchycardia: SVT v/s VT
QRS duration
<0.14
>0.14
s/o AV dissociation (fusion, capture bts)
absent
may be seen
Response of vagal maneuvers + -
Concordance of QRS complexes in V1-V6
Axis: extreme axis deviation
rare
h/o CAD
uncommon
Usually present

49. 4. Ventricular Fibrillation (VF)
Chaotic depolarization of the ventricles
Loss of organized QRS complexes
Complete loss of the cardiac contractile function
Circulatory arrest comes about within seconds
The most common cause of sudden cardiac
death

50. Ventricular Fibrillation

51. Ventricular Fibrillation

52. General Rule for Arrhythmia Rates
Rhythm Rate (bpm)
• Normal Sinus Rhythm – 100
• Idioventricular “Escape” Rhythm – 40
• Junctional “Escape” Rhythm – 60
• Accelerated Idioventricular (AIVR) – 120
• Sinus Tachycardia (ST) – 150
• *SVT & Ventricular Tach. (VT) – 250
• Atrial Flutter & Torsades de Pointes – 350
• Atrial Fib. & Ventricular Fib – 450
* Excludes ST, atrial fibrillation & atrial flutter

53. D. Arrhythmias: Review!

54. Regular Narrow-Complex Tachycardias
Sinus Tachycardia: Normal P-waves, HR usually <150 bpm
Proxysmal Atrial Tachycardia (PAT): P-waves are different from sinus (may be inverted) or absent
Atrial Flutter: Large “saw-toothed” flutter-waves, +/– variable AV-block
AV-Nodal Re-entrant Tachycardia (AVNRT): Most common form of PSVT, +/– P-waves
AV Re-entrant Tachycardia (AVRT): A common form of PSVT, +/– P-waves, + accessory pathway

55. Irregularly Irregular Narrow-Complex Tachycardias
Atrial Fibrillation: No recognizable P-waves
Multifocal Atrial Tachycardia (MAT): Three (3) consecutive P-waves with different morphologies, usually associated with COPD
3. Any “regular” SVT with variable AV-block: Examples: PAT or a. flutter with variable AV-block

56. Approach to EKG Interpretation
ALWAYS, ALWAYS, ALWAYS:
1. Rate
2. Rhythm (includes analysis of intervals)
3. Axis
4. Hypertrophy
5. Ischemia, Injury, or Infarct

57. Atrial (non-sinus) Rhythm

58. Multifocal Atrial Tachycardia

59. Atrial Flutter with 2:1 Conduction

60. Sinus Rhythm with Unifocal PVC’s

61. Atrial Fibrillation with a Slow Ventricular Response

62. Sinus Rhythm with Bigeminal PVC’s

63. Atrial Fibrillation with RVR

64. Thank you for your attention!
The End
Thank you for your attention!
Questions?