1
Myocardial Infarction
Definition:
Death of heart tissue
Due to
Obstruction of blood flow
2
AMI - Critical Concept
 AMI is not a single event
 It is a rapidly evolving process
The Goal:
Identify, Intervene, and
STOP HEART MUSCLE DEATH
3
Prehospital Issues

900,000 Americans experience AMI
annually

125,000 die in the field

Most deaths are arrhythmic

Paramedics must act with urgency
5
Acute Myocardial Infarction (AMI)
Prehospital Standard of Care 
Patient Assessment

12 Lead ECG Screening

Thrombolysis Screening
6
Standard of Care Rationale
 Leading cause of death:
Coronary Disease
 Cause of most AMIs:
Thrombus
 Reduce time to Rx:
Prehospital ECG
 Early Rx (Thrombolytics):
Saves Lives
“Time is Muscle”
7
The Prehospital ECG in AMI
Although adds prehospital time:

Shortens in-hospital treatment time

Patient’s more likely to receive thrombolytics
Or percutaneous transluminal coronary
Angioplasty (PTCA)

Significantly reduces patient mortality
8
Areas of Delay
 Patient
 Prehospital
 Hospital
GOAL: 60 Minutes to Treatment
9
Cardiac Checklist - Key Components

Focused History

12 Lead ECG

Physical Examination

Thrombolytic Criteria
10
EMS System
Pre-Hospital Protocol

Oxygen - IV - cardiac monitor - vital signs

Nitroglycerin

Aspirin

Pain relief with narcotics

Notification of emergency department

Rapid transport to emergency department

Prehospital screening for thrombolytic therapy

12-lead ECG, computer analysis, transmission to
emergency department
11
Hospital Protocol
Time interval
in Emergency
Department
 “DOOR-TO-DRUG” TEAM PROTOCOL
E.D.
APPROACH
 Rapid triage of patients with chest pain
 Clinical decision maker established
(physician, cardiologist, or other)
12
13
12 Lead EKG Placement
14
Lead Placement
16
Good Lead Placement?
17
18
EKG Vectors
 EKG machines measure the force and
direction of the depolarization waves
produced when the heart depolarizes.
 Something that has force and direction is
a vector
19
EKG Vectors
 Multiple vectors are pulling on the circle, but
the circle can ONLY MOVE IN ONE DIRECTION,
THE RESULTANT DIRECTION.
SA Node
Resultant Vector
20
EKG Vectors
 SA Node depolarizes
SA Node
21
Detecting EKG Vectors
-
+
22
Detecting EKG Vectors
-
+
23
Positive Vectors
-
+
24
Positive Vectors
-
+
25
Negative Vectors
-
+
26
EKG Vectors
Where the positive and negative electrodes
are placed on the body, determines where
the positive and negative fields are located.
27
Lead II
-
+
28
Lead III
-
+
29
Lead III
-
+
30
Normal Vector Directions
 Atria depolarize
 Which lead will be best for seeing vector?
 Which lead will be the worst?
31
Normal Vector Directions
 Ventricles depolarize
 Which lead will be best
for seeing vector?
 Which lead will be the
worst?
32
Augmented Voltage Leads
 Need more than 3 Leads
 Augmented voltage leads produced.
 These leads require the EKG machine to
manipulate voltages.
33
Augmented Voltage Leads
AVF
-
+
34
Augmented Voltage Leads
AVL
+
35
Augmented Voltage Leads
AVR
+
36
Frontal Leads
6 frontal leads used.
AVR
AVL
I
III
AVF
II
37
Frontal Plane Leads
38
Frontal Leads
I
aVL
 II
 III
I
 AVR
 AVL
 AVF
aVR
III
II
aVF
39
Bipolar Limb Leads
 Lead I
 Lead II
 Lead III
 Einthoven’s
Triangle
40
Unipolar or Augmented Limb Leads
 Lead aVR
 Lead aVL
 Lead aVF
41
The Hexaxial and Semicircle Reference Systems
42
43
Chest Leads
 Frontal Leads look at
– Left & right side of heat
– Inferior side of heart
 Chest Leads
– Anterior / Posterior
44
Precordial Leads
6 Precordial leads
 forward or backward
 left or right
45
Chest Leads
 V1
Center of Heart
zero point
 V2
-
-
Posterior
-
 V3
 V4
 V5
 V6
V6
-
+
-
+
+
V1
+
+
V2
V5
+
V4
V3
Anterior
46
Vertical and Horizontal Planes
Limb Leads
(Vertical Plane)
Chest Leads
(Horizontal Plane)
Center of Heart
zero point
aVL
-
-
Posterior
-
I
aVR
III
II
aVF
+
-
+
+
V1
+
+
V2
+
V6
V5
V4
V3
Anterior
47
The Normal 12 Lead
48
ECG Leads (3 of 8)
49
50
Quadrants
51
Normal Ventricular Axis
52
Axis Grid System
Extreme Right
Axis deviation
Left Axis Deviation
(No Mans Land)
Right Axis
Deviation
Normal Axis
53
Axis
Normal Axis Range
54
Positive Poles
+
+ AVF
I
55
Determining Axis Deviation
I
Lead I
+ AVF
56
Determining Axis Deviation
Lead AVF
+ AVF
57
Normal Axis
+
+ AVF
I
58
Determining Axis Deviation
I
Lead I
+ AVF
59
Determining Axis Deviation
Lead AVF
+
+ AVF
60
Left Axis Deviation
+
+ AVF
I
61
Determine Axis
 Lead I
 Lead AVF
62
Right Axis Deviation
+
+ AVF
I
63
Ventricular Tachycardia
 Lead I
 Lead AVF
 where will this vector be located
64
Right Axis Deviation
 Abnormal finding
 Often associated
with COPD and
pulmonary
hypertension
65
Left Axis Deviation
 Abnormal finding
 Often associated with
hypertension, valvular heart
disease, and other disease
processes

66
Axis Deviation
 Determining Axis Deviation
67
Axis Deviation
 Determining Axis Deviation
68
69
The Normal 12 Lead
 Each lead looks at different part of the heart
70
Locations and Leads
LOCATIONS
LEADS
Inferior
II, III, aVF
Septal
V1 – V2
Anteror
V2 – V4
Lateral
I, aVL, V5, V6
71
72
Normal Electrocardiogram
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
73
74
Acute Myocardial Infarction
75
ST & T Wave Changes
Normal
T Wave Inversion
ST Depression
ST Elevation
Q Wave / ST
Elevation
Q Wave / Normal ST
/ Inverted T
76
Ischemia
77
Injury
78
Transmural Q wave Infarction
Lead I
Lead III
Lead II
79
80
81
82
Infarction
83
Resolution
84
ST – T Waves changes in AMI
85
Ischemia
 Inverted T waves in 2 congruent leads
– Normal in V1 and III
 ST segment
depression
86
Injury
– ST elevation >1mm in 2 congruent leads
87
Infarction
 Path Q waves
– >.04 sec wide or 1/3 of R, with ST elevation
88
STEMI
 Criteria
 Other cardiac patients
89
Evolution of Acute Myocardial Infarction
90
Evolution of Acute Myocardial Infarction
91
Evolution of Acute Myocardial Infarction
Subendocardial Infarction
92
93
Bundle Branch Blocks
 Right Bundle
 Left Bundle
– Anterior Fascicla
– Posterior Fascicula
94
Bundle Branch Blocks
 Slows conduction
 Increases QRS duration
 May cause problems
reading ST segemet
changes
95
Right Bundle Branch Block
96
Left Posterior Hemiblock
97
The Turn-Signal Rule
1.
QRS >0.12 seconds throughout the ECG.
2.
Look at the QRS in V1.
3.
Identify the J point.
4.
Draw a horizontal line.
5.
Triangle pointing up RBBB.
6.
Triangle pointing down LBBB.
98
Bundle Branch Block - QRS  .12 sec.
Lead V1 - turn signal:
QRS
down = left
QRS
up = right
Left BBB
Right BBB
99
Complete Left Bundle Branch Block
I
aVR
II
aVL
III
aVF
V1
V2
V3
V4
V5
V6
100
Complete Right Bundle Branch Block
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
101
102
Step 1
 Rate
 Rhythm interpretation
103
Step 2: P waves in Lead I or AVR
I
aVR
V1
V4
II
aVL
V5
III
aVF
V6
104
Step 3. Lead V1 for BBB
Lead V1 - turn signal:
QRS
down = left
QRS
up = right
Left BBB
Right BBB
105
Step 4: Normal R wave progression in V Leads
106
Step 5
 T wave changes
 ST Segment changes
 Q Waves
107
108
Inferior Leads
109
Inferior
110
Inferior MI (II, III, aVF)
III
I
aVR
V1
V2
V4
II
aVL
V3
V5
III
aVF
V3
V6
aVF
II
111
Anterior Leads
112
Anterior
113
Anterior MI (V1 - V6)
V6
V1
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
V2
V3
V5
V4
114
Lateral Leads
115
Lateral
116
High Lateral Leads
117
1,1,
aVL
aVL
Lateral MI (I, aVL, V5, V6)
V1
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
V2
V3
V6
V5
V4
118
Anteroseptal MI (V1 - V4)
V6
V1 V2
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
V3
V5
V4
119
Inferior MI - Initial ECG
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
(1 of 3)
120
Inferior MI - Interim ECG
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
(2 of 3)
121
Inferior MI - Discharge ECG
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
(3 of 3)
122
True Posterior Leads
123
True Posterior
124
MI - Anterior
Septal
125
MI -Anterior
126
MI - Septal
127
128
MI - AL
129
MI Lateral
130
MI Posterior
131
Anterior Lateral Inferior
132
Anterolateral Leads
133
Inferolateral Leads
134
135
136
137
Chamber Enlargement
 Atrial Enlargement
 Ventricular Hypertrophy
 Causes
– Right-sided enlargement and hypertrophy, usually
secondary to long-term pulmonary disease
– Left-sided enlargement and hypertrophy, usually
secondary to long-term hypertension
138
Right Atrial Enlargement
139
Right Atrial Enlargement
140
Left Atrial Enlargement
141
Left Atrial Enlargement
142
Right Ventricular Hypertrophy
143
Right Ventricular Hypertrophy
144
Left Ventricular Hypertrophy
145
Left Ventricular Hypertrophy
146
147
ECG Mimics of AMI - History May Help!
Complete LBBB
Early Repolarization
LV Hypertrophy
Ventricular Rhythms
Ventricular Pacemaker
Pericarditis
Sequential Pacemaker
148
Complete Left Bundle Branch
Block
V1
 Sinus P with wide QRS
V6
(> 3 small boxes)
 LBBB and history suggestive of acute MI
(Class I recommendation for thrombolysis)
149
Complete Left Bundle Branch Block
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
150
Left Ventricular Hypertrophy (LVH)
I
V5
 Tall R waves in leads reflecting L.V.
(R wave V5 or V6 > 26 mm)
 ST - T changes due to L.V.H.
151
Left Ventricular Hypertrophy
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
152
Ventricular Pacemaker
II
V5
 Spike followed by wide QRS
 Cannot interpret ST - T waves
153
Ventricular Pacemaker
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
154
A-V Sequential Pacemaker
III
V3
 Spike followed by P wave
 2nd spike followed by wide QRS
155
A-V Sequential Pacemaker
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
156
Early Repolarization
V4
V5
 J and concave ST elevation V leads
 Normal variant / young males
157
Early Repolarization
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
158
Ventricular Dysrhythmia
III
V4
 QRS wide and unrelated to P waves
 Cannot interpret ST - T waves
159
Ventricular Dysrhythmia
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
160
Acute Pericarditis
I
V6

ST segment elevation most leads

“Flu” history and atypical chest pain
161
Acute Pericarditis
I
aVR
V1
V4
II
aVL
V2
V5
III
aVF
V3
V6
162
Indications for 12 Lead ECG Include:
“Chest Pain”
Palpitations/Dysrhythmias
Shortness of Breath
Overdoses
Syncope / Dizziness
Impending Doom
Unexplained Sweating or Nausea and Vomiting
163
CAUTIONS:
 First treat life threatening problems and
chest pain
 Do not delay transport of critically ill
patients
164
Transmural AMI
Ischemia:
Injury:
Infarction:
T
Inversion
ST
Elevation
Q Wave
(Pathologic)
165
AMI Extent and Progression
LV
Subendocardial
V5
ST Segment
Depression
Non Transmural
(Non Q Wave)
V5
T Wave
Inversion
Transmural
Thrombus Usual
V5
Q Wave and ST
Segment Elevation
166
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170
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