1. BASIC ECG INTERPRETATION
2015

2. Conduction System Review

3. CARDIAC CELLS Current Voltage
Electrical charge flow from one point to another
Voltage
Energy measurement between positive and negative points
Measured in millivolts

4. CARDIAC CELLS Action Potential
Five Phase cycle reflecting the difference in concentration of electrolytes (Na+, K+, Ca++, Cl-) which are charged particles across a cell membrane
The imbalance of these charged particles make the cells excitable

5. Cardiac Cell Action Potential
Phase 0
Depolarization
Rapid Na+ entry into cell
Phase 1
Early depolarization
Ca++ slowly enters cell
Phase 2
Plateau-continuation of repolarization
Slow entry of Sodium and Calcium into cell

6. Cardiac Cell Action Potential
Phase 3
Potassium is moved out of the cell
Phase 4
Return to resting membrane potential

7. CARDIAC CELLS
Current (flow of energy) of electrolytes from one side of the cell membrane to the other requires energy (ATP)
Expressed as volts
Measured as ECG

8. CARDIAC CELLS Properties Automaticity Excitability
Cardiac pacemaker cells create an electrical impulse without being stimulated from another source
Excitability
Irritability
Ability of cardiac muscle to respond to an outside stimulus, Chemical, Mechanical, Electrical

9. CARDIAC CELLS 3.Conductivity 4.Contractility
Ability of cardiac cell to receive an electrical impulse and conduct it to an adjoining cardiac cell
4.Contractility
Ability of myocardial cells to shorten in response to an impulse

10. CONDUCTION SYSTEM Sinoatrial Node (SA) Primary pacemaker
Intrinsic rate /min
Located in Rt. Atrium
Supplied by sympathetic and para- sympathetic nerve fibers
Blood from RCA-60% of people

11. CONDUCTION SYSTEM Atrioventricular Junction Internodal pathways merge
AV Node
Non-branching portion of the Bundle of His

12. CONDUCTION SYSTEM AV Node Supplied by RCA – 85%- 90% of people
Left circumflex artery in rest of people
Delay in conduction due to smaller fibers

13. CONDUCTION SYSTEM Bundle of His
Located in upper portion of interventricular septum
Intrinsic rate /min
Blood from LAD and Posterior Descending
Less vulnerable to ischemia

14. CONDUCTION SYSTEM Right & Left Bundle Branches
LBB – Left Bundle Branch
Anterior Fasicle
Anterior portion left ventricle
Posterior Fascicle
Posterior portions of left ventricle
Septal Fasicle
Mid-spetum
RBB – Right Bundle Branch
Right Ventricle

15. CONDUCTION SYSTEM Purkinje Fibers Intrinsic pacemaker rate 20-40/min
Impulse spreads from endocardium to epicardium

16. The ECG

17. ECG Records electrical voltage of heart cells Orientation of heart
Conduction disturbances
Electrical effects of medications and electrolytes
Cardiac muscle mass
Ischemia / Infarction

18. ECG Leads Tracing of electrical activity between 2 electrodes
Records the Average current flow at any specific time in any specific portion of time

19. ECG Types of leads Limb Lead (I, II, III)
Augmented (magnified) Limb Leads (aVR, aVL, aVF)
Chest (Precordial) Leads (V1,V2,V3,V4,V5,V6)
Each lead has Positive electrode

20. ECG Each lead ‘sees’ heart as determined by 2 factors
1. Dominance of left ventricle
2. Position of Positive electrode on body

21. ECG
Lead I
Negative electrode
Right arm
Positive electrode
Left arm

22. ECG
Lead II
Negative Electrode
Right Arm
Positive Electrode
Left Leg

23. ECG
Lead III
Negative Lead
Left Arm
Positive Lead
Left Leg

24. ECG PAPER Graph Paper Small boxes Horizontal axis 1mm wide; 1 mm high
Time in seconds
1 mm box represents seconds
ECG paper speed is 25 mm/second
One large box is 5 small boxes and =.20 seconds (.04sec x5)

26. ECG PAPER Waveforms Movement from baseline Positive (upward)
Negative (downward)
Isoelectric –along baseline
Biphasic - Both upward and downward

27. ECG P Wave First waveform Impulse begins in SA Node in Right Atrium
Downslope of P wave – is stimulation of left atrium
2.5 mm in height (max)
O.11 sec. duration (max)
Positive in Lead II

29. A normal ECG waveform

30. ECG QRS Complex Electrical impulse through ventricules
Larger than P wave due to larger muscle mass of ventricles
Follows P wave
Made up of a
Q wave
R wave
S wave

31. ECG Q wave First negative deflection following P wave
Represents depolarization of the interventricular septum activated from left to right

32. ECG S wave Normal duration of QRS
Negative waveform following the R wave
Normal duration of QRS
0.06 mm – 0.10 mm
Not all QRS Complexes have a Q, R and S

33. ECG T wave Represents ventricular repolarization
Absolute refractory period present during beginning of T wave
Relative refractory period at peak
Usually 0.5 mm or more in height
Slightly rounded

34. ECG
U wave
Small waveform
Follows T wave
Less than 1.5 mm in amplitude

36. ECG
J Point
Point where the QRS complex and ST-segment meet

38. ECG
PR Interval
Measurement where P wave leaves baseline to beginning of QRS complex
sec.
QRS Interval
Measurement from beginning of the Q wave until the end of the S wave.
sec.

39. ECG
QT interval
Begins at isoelectric line from end of S wave to the beginning of the T wave sec.
Represents total ventricular activity
Measured from beginning of QRS complex to end of T wave.

40. ECG Analysis Determine Rate Is it Regular? ( R-R and P-P intervals)
Normal? Fast? Slow?
Atrial Rate? Ventricular Rate?
Is it Regular? ( R-R and P-P intervals)
Regularly irregular ( pattern) or irregularly irregular?
Are P-waves Present?
Are there p waves before every QRS?
Is the P-P interval constant?
Is The P-R interval normal?
Is the QRS normal?
Is the morphology of the QRS the same?

41. ECG Analysis Determining Rate Rate Six Second Method
Two – 3 second markers
Count complexes and multiply x 10

47. ECG Normal Sinus Rhythm Electrical activity activity starts in SA node
AV Junction
Bundle Branches
Ventricles
Depolarization of atria and ventricles
Rate: /Regular
PR interval / QRS duration normal

51. ECG Sinus Bradycardia Sinus Node fires at a rate slower than normal
Conduction occurs through atria, AV junction, Bundle Branches and Ventricles
Depolarization of atria and ventricles occurs
In adults – rate is slower than 60 / minute
Rate is regular
Why?
Athletes Vagal Stimulation
Medications Cardiac disease

52. ECG Sinus Bradycardia Causes H’s T’s Hypoxia Hypovolemia
Hydrogen Ion (acidosis)
Hypo- Hyperkalemia
Hypoglycemia
Hypothermia
T’s
Toxins
Tamponade
Tension Pneumothorax
Thrombosis
Trauma

54. ECG Sinus Tachycardia SA node fires faster than 100-180/minute
Normal pathway of conduction and depolarization
Regular rate
Why?
Coronary artery disease; Fear; anger; exercise;
Hypoxia;Fever
Treatment:
Treat Cause
Beta-Blockers

57. ECG Sinus Arrhythmia The SA node fires Irregularly / Rate 60-100/min.
Normal pathway of electrical conduction and depolarization
PR and QRS durations are normal
Why?
Respiratory- Increases with inspiration; decreases with expiration
Often in children; Inferior Wall MI; Increased ICP;
Medications: Digoxin; Morphine

60. ECG
Sinus Arrest
SA node fails to initiate electrical impulse for one or more beats
May see no beats on monitor or other pacemaker cells in the heart may take over
Rate: Variable ; Rhythm: Irregular
Why?
Hypoxia; Coronary artery disease; Hyperkalemia
Beta-Blockers; CA channel blockers; Increased vagal tone

63. ECG Premature Atrial Complexes
An electrical cell within the atria fires before the SA node fires
Rate: Usually closer to 100; Irregular rhythm
P wave usually looks abnormal and complex occurs before it should
Why?
Emotional stress; CHF; Acute coronary syndromes
Stimulants; Digitalis Toxicity; etc.

64. ECG

65. ECG

66. ECG

67. ECG Supraventricular Tachycardiac (SVT) S & S
Fast rhythms generated ‘Above the Ventricles’
Paroxysmal SVT (starts or ends suddenly)
Rate – usually
Why? Stimulants; Infection; Electrolyte Imbalance
MI; Altered atrial pathway (WPW)-Kent
S & S
Lightheadedness; Palpitations; SOB; Anxiety; Weakness
Dizziness; Chest Discomfort; Shock

68. ECG

69. ECG

70. ECG
Atrial Flutter
Irritable focus within the atrium typically fires at a rate of about 300 bpm
Waveforms resemble teeth of a saw
AV node cannot conduct faster than about 180 beats/minute
Atrial vs ventricular rate expressed as a ratio
Why: Re-entry- Hypoxia Pulmonary embolism
MI Chronic Lung disease Pneumonia etc.
S & S: SOB; Weakness; Dizziness; Fatigue; Chest discomfort

71. ECG

72. ECG
                                                                                                                               

73. ECG

74. ECG Atrial Fibrillation
Irritable sites in atria fire at a rate of /minute
Muscles of atria quiver rather than contract (fibrillate)
No P waves – only an undulating line
Only a few electrical impulses get through to the ventricles – may be a lot of impulses or a few
A lot of impulses (ventricular rate high- then called atrial fibrillation with rapid ventricular response)
A few impulses (ventricular rate slow – then called atrial fibrillation with slow ventricular response)

75. ECG

76. ECG

77. ECG

78. ECG Delay or interruption in impulse conduction
AV Block
Delay or interruption in impulse conduction
Classified according to degree of block and/or to site of block
First Degree Block
Impulses from SA node to the ventricles is DELAYED but not blocked
Why?
Ischemia
Medications
Hyperkalemia
Inferior MI
Increased Vagal Tone

79. ECG

80. ECG

81. ECG

82. ECG Lengthening of the PR interval and then QRS wave is dropped Why?
Second Degree Block Type I - Wenckebach
Lengthening of the PR interval and then QRS wave is dropped
Why?
Usually RCA occlusion (90% of population)
Ischemia
Increase in parasympathetic tone
Medications

83. ECG

84. ECG
The dropped QRS

85. ECG

86. ECG Why Second Degree AV Block – Mobitz Type II Important:
Ischemia LCA – Anterior MI
Organic heart disease
Important:
Ventricular Rate
QRS duration
How many dropped QRS’s in relation to P waves?
What is the ratio?

87. ECG

88. ECG

89. ECG No P waves are conducted to the ventricles
Third Degree AV Block (Complete Block)
No P waves are conducted to the ventricles
The atrial pacemakers and ventricle pacemakers are firing independently
Why?
Inferior MI
Anterior MI
Serious

90. ECG

91. ECG

92. ECG

93. ECG Are the heart’s least efficient pacemakers
Ventricular Rhythms
Are the heart’s least efficient pacemakers
Generate impulses at 20-40/min
They assume pace-making if:
SA nodes fail, very slow (below 20-40) or are blocked
Ventricles site(s) is irritable
Irritable due to ischemia
Depolarization route is abnormal and longer, therefore QRS looks different and is wider.
T wave is opposite in direction to QRS

94. ECG Called Unifocal (from one focus or foci)
Premature Ventricular Contractions
May be from One Site and all look the same
Called Unifocal (from one focus or foci)

95. ECG
May be from Different sites (Foci) and are called Multifocal PVC’s

96. ECG
May occur every other beat – Ventricular Bigeminy

97. ECG
May occur every third beat – Ventricular Trigeminy

98. ECG
R on T PVC

99. ECG

100. ECG
Couplets (2 PVC’s in a row); Triplets (3 PVC’s in a row)

101. ECG
Couplets also known as ‘Salvos’.

102. ECG
Run of PVC’s
Ventricular Tachycardia

103. ECG
Ventricular Tachycardia
Defined as Three or more PVC’s occurring in a row at a rate > 100/min
Wide QRS
No P waves
No T waves
Why?
Ischemia
Infarction
Congenital
Usually lethal
S & S: Weakness, Dizziness, Shock, Chest Pain,Syncope

104. ECG

105. ECG

106. ECG
Torsades de Pointes (Twisting of the Points)
Ventricular Tachycardia in which the QRS changes in shape, amplitude and width
Causes:
Hypomagnesium
Hypokalemia
Quinidine therapy
S & S:
Altered mental status, shock, Chest pain, SOB, Hypotension

107. ECG

108. ECG

109. ECG Chaotic rhythm of the ventricles Lethal if not treated Causes:
Ventricular Fibrillation
Chaotic rhythm of the ventricles
Lethal if not treated
Causes:
AMI
Electrolyte Imbalance
Drug OD’s
Trauma
Heart Failure
Vagal Stimulation
Increased SNS
Electrocutions
Congenitial Heart defects

110. ECG

111. ECG Pulseless Electrical Activity – PEA
Rhythm on monitor but no corresponding pulse
Why? Look for Cause!
H’s and T’s
Hypoxia Toxins
Hypovolemia Tamponade, cardiac
Hydrogen Ion (acidosis) Tension Pneumothorax
Hypo-Hyperkalemia Thrombosis (coronary or pulmonary)
Hypoglycemia Trauma (Increased ICP, hypovolemia
Hypothermia

112. ECG

113. ECG Asystole No electrical activity on monitor No pulse
Why? Look for Cause!
H’s and T’s
Hypoxia Toxins
Hypovolemia Tamponade, cardiac
Hydrogen Ion (acidosis) Tension Pneumothorax
Hypo-Hyperkalemia Thrombosis (coronary or pulmonary)
Hypoglycemia Trauma (Increased ICP, hypovolemia)
Hypothermia

114. Thanks for Coming!
Questions?