ECG Lecture

1. Electrocardiography
Rigil Kent A. Franco, RN, MD
1st Year Resident
Emergency Medicine
Fatima University Medical Center

2. Electrocardiography
▲ Graphic recording of electric potentials produced
by the heart.
▲ Signals detected by metal electrodes attached to
extremities and chest wall and recorded by the
ECG machine.
▲ Noninvasive, inexpensive and readily available.

3. Unipolar Precordial Leads
V1 - 4th ICS right sternal margin
V2 - 4th ICS left sternal margin
V3 - midway between V2 and V4
V4 - 5th ICS MCL
V5 - AAL same level as V4
V6 - MAL same level as V4

5. Leads
LI
LII
LIII
AVR
AVL
AVF
V1
V2
V3
V4
V5
V6
View of Heart
Lateral wall
Inferior wall
Inferior wall
No specific view
Lateral wall
Interior wall
Anteroseptal wall
Anteroseptal wall
Anterior wall
Anterior wall
Anterolateral wall
Anterolateral wall

9. P wave
● represents atrial depolarization
● atrial conduction time
● normal amplitude is 0.5 to 2.5 mm
● normal duration is up to 0.10s in adults
● usually biphasic in V1

10. P-R Interval
● represents time interval for impulse to reach
ventricles from SA node
● measured in limb lead with longest PR interval
● normal is 0.12-.20s in adults (HR = 70-90/min)

12. QRS Complex
Q wave - initial downward deflection
R wave - first upward deflection whether preceded by a
Q wave or not
S wave - downward deflection following the R wave
QS wave - single negative deflection representing entire QRS
R’ wave - second upward deflection
S’ wave – downward deflection following the R’ wave

15. ST Segment
● represents period from end of ventricular depolarization
to start of ventricular repolarization
● between end of QRS and start of T wave
● clinically important if elevated or depressed as it
may represent infarction or ischemia
● usually isoelectric but may be depressed –0.5 mm
or elevated by 1mm.

21. S-T depression

22. T wave
● represents ventricular repolarization
● usually upright in LI, LII and diphasic
or inverted in LIII, V1
● maybe inverted up to V3 in young adults
● T wave in V6 usually > V1
● physiologic T wave changes maybe seen in
body position, fever, skeletal abnormalities,
hyperventilation , fever, etc.

23. Q-T Interval
● represents electrical systole
● time required for ventricular depolarization
and repolarization
● varies with age sex and heart rate
● normal QT is 0.35-0.44s in adults
● Corrected QT or QTc
Q-Tc = Q-Ts
● Prolonged QTc > 0.425s
R-R interval (s)

25. U wave
● small deflection after the T wave
● represents repolarization of the Purkinje fibers
● tallest in V2 & V3
● usually does not exceed >1mm in amplitude
● same as T wave polarity
● increased amplitude in LVH, hypokalemia, drugs etc.
● negative U wave specific for heart disease

27. STEPS IN BASIC ECG
READING
1. Determine Rate
2. Determine Rhythm
3. Measure Intervals
4. Determine QRS electrical axis
5. Check for chamber enlargements
6. Inspect QRS complexes for bundle branch block or fascicular block
7. Check for ST and T wave changes
8. Check for miscellaneous ECG findings

28. • In determining the heart rate in regular rhythm,
• count the number of small squares between two successive QRS
complexes.
• The numerator (1500) is a constant, and when divided by 20
(number of small squares between successive QRS complexes),
yields a heart rate of 75 beats per minute.
DETERMINING THE RATE

29. • In determining the heart rate in an irregular rhythm,
• count the number of QRS complexes within the 6 second strip.
• This value should be multiplied by 10 in order to yield the heart rate
in 1 minute.
DETERMINING THE RATE

30. DETERMINING THE RHYTHM

31. DETERMINING THE RHYTHM

32. DETERMINING THE RHYTHM

33. DETERMINING THE RHYTHM

34. Electrical Axis

35. Electrical Axis

36. CHAMBER ENLARGEMENTS

37. Left Atrial Hypertrophy
● P wave duration > 0.12s
● Biphasic P wave in V1 & V2 with negative
terminal portion having depth of >0.1 mV

38. V1
LII

40. Right Atrial Enlargement
● P waves tall (> 0.25mV) & peaked
in inferior leads
● Biphasic P wave in V1 with first component
larger than the second

41. Right Atrial Enlargement

42. Right Atrial Enlargement

43. Right Ventricular Hypertrophy
● R/S ratio in V1 > 1
● S in V1 < 2mm
● RAD > 110 degrees

44. Right Ventricular Hypertrophy

45. Left Ventricular Hypertrophy
Sum of R wave in V5 or V6 + S wave in V1 or V2
> 35mm in > 30 year olds
>40 mm in 20-30 year olds
>60 mm in 6-20 year olds

47. STEPS IN BASIC ECG
READING
1. Determine Rate
2. Determine Rhythm
3. Measure Intervals
4. Determine QRS electrical axis
5. Check for chamber enlargements
6. Inspect QRS complexes for bundle branch block or fascicular block
7. Check for ST and T wave changes
8. Other ECG tracings

50. PREMATURE ATRIAL CONTRACTIONS
• A longer PR interval
• Premature atrial contractions may occur in a pattern, such as every other beat (atrial bigeminy), every third beat
(atrial trigeminy), and so on.
• Common at all ages and usually do not indicate underlying heart disease.
• Increased rates of premature atrial contractions are seen in patients with chronic heart or lung disease

51. PREMATURE VENTRICULAR
 Many PVCs occurring in a bigeminal or trigeminal pattern have a fixed coupling
interval (within 40 milliseconds) from the preceding sinus beat
 The degree is categorized into:
 Occasional / Isolated
 Multiple of similar morphology / Unifocal
 Multiple with different morphology / Unifocal

52. BRADYDYSRHYTHMIAS

53. JUNCTIONAL RHYTHM
 Usually do not require specific treatment.
 Atropine can be used to accelerate the SA node
discharge rate and enhance AV nodal conduction.
 Accelerated junctional rhythm and junctional
tachycardia are managed by treating the
underlying cause.

54. IDIOVENTRICULAR RHYTHM
 Regular widened QRS complexes without evidence of atrial activity
 Atropine can be tried, although the likelihood of successful treatment is low.
 Cardiac pacing is often needed, starting via the transcutaneous route.

55. SUPRAVENTRICULAR
TACHYDYSRHYTHMIAS

56. ATRIAL FIBRILLATION AND ATRIAL FLUTTER
 Treated with Ventricular Rate Control and/or Synchronized Cardioversion
 Atrial Fibrillation – 150-200J
 Atrial Flutter - May require as little as 25–50 J

57. MULTIFOCAL ATRIAL TACHYCARDIA
 An irregular rhythm resulting from at least three different atrial foci competing to
pace the heart, resulting in distinct P-wave morphologies on the ECG.
 Found most often in elderly patients with decompensated chronic lung disease,
but may also complicate heart failure or sepsis.
 Vagal maneuvers are often effective

58. Paroxysmal supraventricular Tachycardia
 Seen more frequently in females, with a peak in the late teenage and young adult
years.
 Palpitations, lightheadedness, and dyspnea are common symptoms.
 Attention to technique is important to maximize
success rate. If there is no response to vagal
maneuvers, IV adenosine is recommended to
convert to sinus rhythm.

59. ATRIOVENTRICULAR BLOCKS

60. FIRST-DEGREE ATRIOVENTRICULAR BLOCK
 First-degree AV block occasionally is found in normal hearts.
 Patients with first-degree AV block without evidence of organic heart disease
appear to have no difference in mortality compared with matched controls.

61. SECOND-DEGREE MOBITZ TYPE I (WENCKEBACH’S)
ATRIOVENTRICULAR BLOCK
 There is progressive prolongation of AV conduction (and the PR interval) until an
atrial impulse is completely blocked.

62. SECOND-DEGREE MOBITZ TYPE II
ATRIOVENTRICULAR BLOCK
 The PR interval remains constant across the rhythm strip, both before and after
the nonconducted atrial beats.

63. THIRD-DEGREE ATRIOVENTRICULAR
(COMPLETE HEART BLOCK)
 In third-degree AV block, there is no AV conduction.

64. WIDE-COMPLEX TACHYCARDIAS

65. VENTRICULAR TACHYCARDIA
 Ventricular tachycardia is the occurrence of three or more consecutive
depolarizations from a ventricular ectopic pacemaker at a rate faster than 100
beats/min.
 Monomorphic / Polymorphic

66. VENTRICULAR FIBRILLATION
 Ventricular fibrillation is seen most commonly in patients with severe ischemic
heart disease, with or without an acute myocardial infarction.
 Treatment of pulseless ventricular tachycardia or fibrillation is with electrical
defibrillation along with chest compressions and other advanced life support
measures.

67. CONDUCTION AND
ABNORMALITIES

68. WOLFF-PARKINSON-WHITE

69. BRUGADA SYNDROME
 Brugada syndrome is an inherited disorder of myocardial depolarization that
predisposes young individuals to malignant ventricular dysrhythmias and sudden
death.
 The majority of patients with Brugada syndrome are asymptomatic and are only
found via an incidental ECG.

70. LONG QT SYNDROME
 Prolongation of the QT interval.
 Do not use medications that possess channel blockade effects, impair cardiac
repolarization, prolong the QT interval, and provoke tachydysrhythmias.
 Correct underlying electrolyte abnormalities especially K and Mg.

71. SHORT QT SYNDROME
 A rare but highly lethal entity associated with an increased risk of ventricular
tachydysrhythmias
 Primarily recognized by a shortened QT interval without any need to adjust for
heart rate.
 Afflicted patients have otherwise structurally and functionally normal hearts.

72. THANK YOU!