Leanna R. Miller, RN, MN, CCRN-CSC, PCCN-CMC, CEN, CNRN, CMSRN, NP
Education Specialist
LRM Consulting
Nashville, TN
ST Segment Changes: Identifying MI Mimics
• Objectives
– Evaluate common abnormalities that mimic
myocardial infarction.
– Identify the criteria for pericarditis and evidence –
based interventions.
– Differentiate between pulmonary embolus and
myocardial infarction using diagnostic criteria.
ST Segment Changes: Identifying MI Mimics
 Acute Coronary Syndromes
– Unstable Angina
– Non ST segment Elevation MI
(NSTEMI)
– ST segment Elevation MI
(STEMI)
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
 Acute Coronary Syndromes
– Clinical Symptoms
• typical
• atypical
ST Segment Changes: Identifying MI Mimics
 Acute Coronary Syndromes
– Diagnostics
• Echocardiography
• Lab
–ABGs
–H & H
–enzymes
ST Segment Changes: Identifying MI Mimics
 Acute Coronary Syndromes
– Diagnostics
• ECG (12 or 15 lead)
–T wave inversion
–ST segment elevation
–Q wave
–reciprocal ST segment
depression
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
SITE
INDICATIVE
RECIPROCAL
Septal
V1, V2
None
Anterior
V2, V3, V4
None
Anteroseptal
V1, V2, V3, V4
None
Lateral
I, aVL, V5, V6
II, III, aVF
Anterolateral
I, aVL, V3, V4, V5, V6
II, III, aVF
Inferior
II, III, aVF
I, aVL, V2, V3
Posterior
None
V1, V2
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
Variation to ST – Segment Elevation
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
High acute risk factors for progression to
myocardial infarction or death
– recurrent chest pain at rest
– dynamic ST-segment changes: ST-segment
depression > 0.1 mV or transient (<30 min) STsegment elevation >0.1 mV
– elevated Troponin-I, Troponin-T, or CK-MB levels
ST Segment Changes: Identifying MI Mimics
High acute risk factors for progression to
myocardial infarction or death
– hemodynamic instability within the observation
period
– major arrhythmias (ventricular tachycardia,
ventricular fibrillation)
– early post-infarction unstable angina
– diabetes mellitus
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
AMI
LVH
BBB
Vpace
BER
Pericarditis
LV Aneurysm
Other
ST Segment Changes: Identifying MI Mimics

Acute Pericarditis
• Introduction
– causes physical discomfort
–
predisposition to tachydysrhythmias
ST Segment Changes: Identifying MI Mimics

Acute Pericarditis
•
ECG Criteria
–
ST segment elevation
–
PR segment depression
–
T wave flattening or inversion
–
atrial dysrhythmias
ST Segment Changes: Identifying MI Mimics

Acute Pericarditis
•
ST segment elevation
–
not isolated or discrete segments
–
upward concavity
–
may be notching at the junction of
QRS and ST segment
–
no reciprocal ST segment depression
ST Segment Changes: Identifying MI Mimics

Acute Pericarditis
•
PR interval
–
interval between end of P wave and
beginning of QRS may be depressed
–
most often seen in lead II and V
leads may be only ECG finding
ST Segment Changes: Identifying MI Mimics

Acute Pericarditis
•
T wave flattening or inversion
–
no T wave inversion during acute phase
–
uncomplicated pericarditis: negative
T waves only occur in leads which usually
have negative T waves (aVR & V1)
ST Segment Changes: Identifying MI Mimics

Acute Pericarditis
• Atrial
dysrhythmias
–
SVT in postoperative open heart patient
–
treat with low dose steroids
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics

Acute Pericarditis
•
Complications (pericardial effusion)
–
dampening of electrical output
–
low voltage in all leads
–
ST segment & T wave changes
ST Segment Changes: Identifying MI Mimics

Acute Pericarditis
•
Complications (pericardial effusion)
–
freely rotating heart produces
electrical alternans
ST Segment Changes: Identifying MI Mimics

Dressler’s Syndrome
•
Introduction
– postmyocardial infarction syndrome
–
autoimmune process
ST Segment Changes: Identifying MI Mimics

Dressler’s Syndrome
•
Clinical Presentation
–low
– grade fever
–chest
pain (worsens with deep
breath; lessens with sitting up
and leaning forward)
–pericardial
friction rub
ST Segment Changes: Identifying MI Mimics

Dressler’s Syndrome
•
12 – lead ECG
diffuse ST segment elevation across
the precordial leads
–
ST Segment Changes: Identifying MI Mimics

Dressler’s Syndrome
•
Treatment
–
corticosteroid administration
–
monitor for complications (effusion)
ST Segment Changes: Identifying MI Mimics

Pulmonary Embolus
•
Introduction
–
sudden massive PE produces ECG changes
–
must get 12 – lead to rule out MI
ST Segment Changes: Identifying MI Mimics

Pulmonary Embolus
•
ECG Findings
– RVH with strain
–
RBBB pattern in V1
–
large S wave in Lead I; large Q wave in Lead
III (S1Q3 pattern)
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics

Ventricular Aneurysm
•
Introduction (etiology)
–
myocardial infarction
–
congenital
–
cardiomyopathy
–
inflammatory
–
idiopathic
ST Segment Changes: Identifying MI Mimics

Ventricular Aneurysm
•
Introduction
–
infereolateral wall of LV
–
symptoms include CHF & exercise –
induced syncope (VT)
ST Segment Changes: Identifying MI Mimics

Ventricular Aneurysm
•
ECG Findings
–
persistent ST segment elevation
–
small q wave in II, III, & aVF
–
sustained VT with RBBB morphology
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics

Ventricular Aneurysm
•
Treatment
–
surgical resection
–
antidysrhythmics
–
anticoagulants
–
treat heart failure
–
ablation therapy
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics

Left Bundle Branch Block (LBBB)
•
QRS duration > 0.12 second
•
absence of septal q waves and S wave
in I, aVL, & V5 – 6 (+ complex usually
notched)
• broad QS or rS in V1 – 3 (- complex)
ST Segment Changes: Identifying MI Mimics

Left Bundle Branch Block (LBBB)
•
S – T, T wave changes in leads I,
aVL & V5 – 6 (T wave opposite QRS)
•
delayed intrinsicoid deflection over
left ventricle (V6); normal over V1
ST Segment Changes: Identifying MI Mimics

Left Bundle Branch Block (LBBB)
•
hypertensive heart disease
•
aortic stenosis
•
degenerative changes of the conduction
system
•
coronary artery disease
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
LBBB with Acute Myocardial Infarction
ST Segment Changes: Identifying MI Mimics
Left Ventricular Hypertrophy
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
Left Ventricular Hypertrophy
ST Segment Changes: Identifying MI Mimics
• Brugada Syndrome
– autosomal dominant inheritance (SCN5A)
gene
– sodium channel involvement in 25% of the
patients
– Asian populations (58%)
– high incidence of polymorphic ventricular
tachycardias
ST Segment Changes: Identifying MI Mimics
• Brugada Syndrome
– found in right precordial leads
– prominent J wave
– ST – segment elevation in the absence of
structural heart disease
– three types
ST Segment Changes: Identifying MI Mimics
• Brugada Syndrome
– Type I: ST – segment elevation is
triangular and T waves may be inverted in
V1 – V3
– Type II: downward displacement of ST –
segment (does not reach baseline)
– Type III: middle part of ST segment
touches baseline
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
Brugada Syndrome
ST Segment Changes: Identifying MI Mimics
LBBB
• Infarction Resemblance
– ST segment elevation in the negatively
deflected leads, (V1 – V3)
– QS complexes in the negatively deflected
leads, (V1 – V3)
• Recognition
– Wide QRS
– QS in V1
ST Segment Changes: Identifying MI Mimics
Ventricular Rhythms
• Infarction Resemblance
– ST segment elevation in the negatively
deflected leads, (V1 – V3)
– QS complexes in the negatively deflected
leads, (V1 – V3)
• Recognition
– Wide QRS following pacer spike
– Negative V1 (RV paced)
ST Segment Changes: Identifying MI Mimics
LVH
• Infarction Resemblance
– ST segment elevation in the negatively
deflected leads, (V1 – V3)
• Recognition
– Choose deepest S wave from V1 and V2
– Choose tallest R wave from V5 and V6
– Add deflections of tallest R wave and
deepest S wave
– Suspect LVH if total is > 35
ST Segment Changes: Identifying MI Mimics
Pericarditis
• Infarction Resemblance
– ST segment elements in multiple leads
• Recognition
– ST segment elevation not in anatomical
grouping
– PR segment deprewsion
– Notching of the J point
ST Segment Changes: Identifying MI Mimics
Acute Pulmonary Emboli
• Infarction Resemblance
– RVH with strain pattern
– RBBB pattern in V1
– S1Q3 on frontal plane
• Recognition
– Patient is symptomatic with atypical
cardiac pain
– Elevates BMP
– r/o with spiral CT/angiogram
ST Segment Changes: Identifying MI Mimics
Ventricular Aneurysm
• Infarction Resemblance
– High risk for ventricular dysrhythmias
(VT with RBBB pattern)
– Inferolateral MI
– Persistent ST segment elevation
– Small q wave in II, III, aVL
• Recognition
– Structural abnormality on ECHO
– CHF & exercise – induced syncope (VT)
ST Segment Changes: Identifying MI Mimics
Brugada Syndrome
• Infarction Resemblance
– Ventricular dysrhythmias (polymorphic VT)
– ST segment elevation in right precordial
leads
• Recognition
– Autosomal dominant
– Asian culture
– No structural abnormality noted on ECHO
ST Segment Changes: Identifying MI Mimics
• Prominent J with ST segment elevations
– septal MI
– RV cardiomyopathy
– pericardial effusion
– hypercalcemia
ST Segment Changes: Identifying MI Mimics
• Prominent J with ST segment elevations
– hyperkalemia
– acute pulmonary embolism
– subarachnoid hemorrhage
– tricyclic antidepressant intoxication
ST Segment Changes: Identifying MI Mimics
ST Segment Changes: Identifying MI Mimics
• In Conclusion
– is the patient having a MI?
– a variety of conditions can mimic
infarction
ST segment changes