This document provides an overview of cardiac conduction systems, electrocardiograms, arrhythmias, and how to interpret ECG readings. It defines common arrhythmias like sinus tachycardia, atrial fibrillation, ventricular tachycardia and discusses how to identify them using a 6-step approach examining rate, rhythm, P-waves, P-R interval, QRS complex and the relationship between P-waves and QRS. Examples are given of normal sinus rhythm and various arrhythmias with their characteristic ECG patterns. Special situations and normal variants are also addressed.

1. BY
Rizk Elazhary
MD, Anesthesiology
Benha University

2. Introduction

3. Anatomy of Cardiac Conduction System

4. Physiology of the heart

5. Electrocardiogram  Action potentials
through myocardium
during cardiac cycle
produces electric
currents than can be
measured
 Pattern
 P wave
 Atria depolarization
 QRS complex
 Ventricle depolarization
 Atria repolarization
 T wave:
 Ventricle repolarization

8. What is Arrhythmias?

9. Classification of Cardiac Arrhythmias
 Tachy arrhythmias(Fast).
 Brady arrhythmias(Slow).
 Regular-arrhythmias.
 Irregular-arrhythmias.
 Other arrhythmias.

10. Approach to Arrhythmias

11. The Six Step Approach
 What is the Rate?
 Is the Rhythm Regular?
 Are there P-Waves?
 Is the P-R Interval Normal?
 Is the QRS Complex Normal?
 Is There a P-Wave for Every QRS?

12. Normal Sinus Rhythm
 Rate: 60 - 100
 Regularity: Very
 P-Waves: Present and Normal
 P-R I: 0.12-0.20 sec
 QRS: 0.04-0.12 sec and Normal
 1 P: 1 QRS, no extras or shortages

13. Sinus Tachycardia
 Rate: Over 100
 Regularity: Regular
 P-Waves: Present and Normal
 P-R I: 0.12-0.20 sec
 QRS: 0.04-0.12 sec and Normal
 1 P: 1 QRS, no extras or shortages

14. Sinus Bradycardia
 Rate: Less than 60
 Regularity: Regular
 P-Waves: Present and Normal
 P-R I: 0.12-0.20 sec
 QRS: 0.04-0.12 sec and Normal
 1 P: 1 QRS, no extras or shortages

15. Atrial Fibrillation
 Rate: Usually tachy
 Regularity: Irregular (Irregularly irregular)
 P-Waves: Not Discernible
 P-R I: Undeterminable
 QRS: 0.04-0.12 sec
 P-QRS : Undeterminable

16. Atrial Flutter
 Rate: Usually tachy
 Regularity: Atria Regular
• Ventricles May be Irregular
 P-Waves: Saw tooth Pattern 2:1, 3:1, 4:1...
 P-R I: 0.12-0.20 sec on conducting beat
 QRS: 0.04-0.12 sec
 P-waves outnumber QRS

17. (Paroxysmal) Supra Ventricular Tach
 Rate: 140-220
 Regularity: Regular
 P-Waves: Usually falls within the QRS-T complex (
sometimes not visible)
 P-R I: Shorter than 0.12, or absent
 QRS: 0.04-0.12 sec and Normal
 P-QRS :Undeterminable

18. SVT
 WPW
 Usually based on Hx.
 Delta wave on Q
 Shortened PR-I
 No Verapamil – Accessory Path use increase

19. 1st Degree Heart Block
 Rate: 60 - 100
 Regularity: Very
 P-Waves: Present and Normal
 P-R I: Longer than 0.20 sec
 QRS: 0.04-0.12 sec and Normal
 1 P: 1 QRS, no extras or shortages

20. 2nd Degree Heart Block (Type 1) Wenkebach
 Rate: Can be Normal, or usually brady
 Regularity: Irregular
 P-Waves: Present and Normal
 P-R I: Lengthens until beat is dropped
 QRS: 0.04-0.12 sec and Normal
 P-wave present on conducting beats, increased delay
causes missed QRS

21. 2nd Degree Heart Block (Type 2) Mobitz II
 Rate: Less than 60
 Regularity: Irregular
 P-Waves: Present, 2:1, 3:1, 4:1
 P-R I: 0.12-0.20 sec on conducting beat
 QRS: 0.04-0.12 sec, may begin to widen
 P-wave for every QRS and extras depending on conduction
ratio

22. 3rd Degree Heart Block (CHB)Complete Heart Block
 Rate: Ventricular Rate 40-60
 Regularity: Atria-Regular
• Vent-Regular
 P-Waves: Present and Normal
 P-R I: Atria independent of Ventricles
 QRS: Usually greater than 0.12 sec
 P-waves completely unrelated to QRS Complexes.

23. Junctional Rhythm
 Rate: 40-60
 Regularity: Regular
 P-Waves: Inverted, Retrograde or Absent
 P-R I: Shortened or absent
 QRS: 0.04-0.12 sec
 P-wave for every QRS, sometimes not visible

24. Ventricular Tachycardia
 Rate: 100-220
 Regularity: Regular
 P-Waves: None
 P-R I: None
 QRS: Greater than 0.12 sec

25. Ventricular Fibrillation
 Rate: No ventricular rate
 Regularity: Irregular
 P-Waves: No
 P-R I: No
 QRS: No, unorganized ventricular baseline

26. Asystole
 Rate: 0
 Regularity: N/A
 P-Waves: None
 P-R I: N/A
 QRS: None
(check another lead)

27. Agonal / Idioventricular
 Rate: 20-40
 Regularity: Irregular
 P-Waves: None
 P-R I: N/A
 QRS: Wider than 0.12 sec
(a dying heart)

28. Other Arrhythmias
 Premature Ventricular Contractions
 Premature Atrial Contractions
 Bundle Branch Blocks
 Pacer Considerations (Atrial, Ventricular or Both)

29. Premature Ventricular Contractions
 Wide, Bizarre QRS Complex
 Always identify the underlying rhythm first
 Can appear in couplets, triplets, short runs of V-Tach,
bigeminy and trigeminy
 Can be uni-focal or multi-focal
 Caused by random firing within the ventricles
 Not accompanied by a P-wave

30. PAC’s
 P-QRS Complex appearing in an unexpected location
 Caused by a stimulus from within the Atria, but not from
the SA Node

31. Bundle Branch Block
 Any rhythm having a BBB will have a widened twin
peaked R-Wave

32. Bundle Branch Block

33. Paced Rhythms Various

34. QT Prolongation
 QT represents the ventricular refractory period
 Normal
 Men 450ms
 Women 460ms
 Corrected QT (QTc)
 QTm/√(R-R)
 Causes
 Drugs (Na channel blockers)
 Hypocalcemia, hypomagnesemia, hypokalemia
 Hypothermia
 AMI
 Congenital
 Increased ICP

35. Torsade de pointes
 Torsades de pointes is a polymorphic ventricular
tachycardia . The phrase “torsades de pointes” means
“twisting on a point” which explains the action of the QRS
complex and how it varies from beat to beat. It is a
shockable rhythm.

36. Normal Variants
 Always normal:
 Sinus Arrhythmia
 Supraventricular Extrasystoles
 Partial RBBB
 Often normal:
 Sinus Bradycardia (and pauses in athletes)
 First Degree Heart Block
 Ventricular Extrasystoles
 Left/Right Axis Deviation
 RBBB

37. Special Situations
 Dextrocardia – reverse precordial leads
 Large breasts – don't place electrodes on top of breast
 Bilateral breast implants you should apply V4, V5, and V6
close to the midaxillary line.
 Note patient abnormalities on ECG
 Do not place electrodes on open wounds, burns, or clear
dressings
 Do not allow electrodes to touch one another

38. References
 Pictures and info from:
 Flip and See ECG, 2nd Edition
 Cohn/Gilroy-Doohan
 A great resource
 Paramedic Paramedic Textbook, Revised 2nd Edition
 Mick J. Sanders, Mosby
 ECG’s Made Easy, 2nd Edition
 Barbara Aehlert, RN, Mosby
 Basic Dysrhythmias, Interpretation and Management,
3rd Edition
 Robert J. Huszar, Mosby