Diagnosis of Myocardial Infarction/Ischemia with Bundle Branch Blocks

1
Diagnosis of Myocardial Infarction/Ischemia with
Bundle Branch Blocks

• Mark I. Langdorf, MD, MHPE, FACEP, FAAEM, RDMS
• Chair and Associate Residency Director
• Medical Director
• Department of Emergency Medicine
• University of California, Irvine

2
Objectives

• To understand the interpretation of 12 lead ECG
  with regard to
• Infarction
• Ischemia
• In the presence of
• Right bundle branch block
• Left bundle branch block
• Ventricular paced rhythms
• To understand the utility of decision rules on
  this topic.

3
Take-home Messages

• You can make the diagnosis of acute myocardial
  infarction or ischemia in the face of bundle
  branch blocks or paced rhythm.
• Secondary ST-T wave changes are normal, and go in
  the opposite direction of the last portion of the
  QRS complex.
• Primary ST-T wave changes mean ischemic or
  infarction, and go in the same direction as the
  last portion of the QRS complex.

4
Take-home Messages

• Left bundle branch block that is new or not known
  to be old, in the setting of a clinical picture
  of MI, likely indicates infarction.
• Reperfusion therapy is recommended.
• Serial ECGs may clarify the situation.
• Immediate angiogram is preferred.

5
Cardiac Conduction System
Bachmanns bundle
Sinus node
Internodal pathways
Left bundle branch
AV node
Posterior division
Bundle of His
Anterior division
Purkinje fibers
Right bundle branch
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Truth?

• The diagnosis of myocardial infarction in the
  presence of left bundle branch block is
  impossible.

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Partially true

• True Diagnosis of completed Mi in left bundle
  branch block is difficult
• Q waves may be present with LBBB in the
  precordial leads without anterior infarction.
• ST segment elevation can be hidden in the usual
  repolarization changes.
• But, Q waves in two contiguous lateral leads
  suggest completed MI
• R wave regression from V1-V4 suggests transmural
  necrosis.

8
But

• ongoing ischemia and injury can be detected in
  the presence of LBBB, and may be seen as often as
  they are in the presence of normal cardiac
  conduction.
• Comparison with old ECGs helpful
• Serial ECGs while in the ED also helpful

Fesmire, Annals EM, 2669, 1995
9
Dr. Braunwald says

• Some findings are highly specific and predictive
  (90-100) for MI with left bundle branch block.
• Q waves in at least two contiguous lateral leads
  (I, aVL, V5 and V6)
• R wave regression from V1 to V4
• Primary ST-T wave changes in two or more
  contiguous leads

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ST-T Wave Changes with Bundle Branch Blocks

• Changes are the same with both right and left
• Also applies to LVH with strain
• Secondary means normal, expected
• Primary means abnormal ischemia or infarction

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J point
ST segment
Terminal portion of QRS
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Secondary ST-T Wave Changes

• These are normal, expected
• Terminal portion of the QRS complex is the key
• J point displaced away from the terminal portion
  of the QRS complex
• T wave oriented away from the terminal portion of
  the QRS complex

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Primary ST-T Wave Changes

• Primary abnormal, not a result of BBB
• ST elevation still means injury or infarction
• ST depression still means ischemia
• Exceptions
• Prinzmetals angina reversible ST elevation
• ST depression/T wave inversion can represent
  infarction sub-endocardial or non-Q wave.

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Primary ST-T Wave Changes

• Must be in two contiguous leads
• Inferior
• II and aVF
• III and aVF
• not II and III
• Septal V1 and V2
• Anterior V3 and V4
• Lateral V5, V6, I and aVL (high lateral)

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Primary ST-T Wave Changes

• One major caveat
• Allowed one lead that has concordant terminal QRS
  complex and T wave
• QRS changes from predominately positive
  deflection to predominately negative
• Dont infer ischemia/infarction if only one lead

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Concept of Dis/Concordance

• Refers to whether the last portion of the QRS
  complex goes in the same or different direction
  as the T wave
• Discordancegood
• Concordancebad

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ECG of Evolving MI with Left Bundle Branch Block

• Review of 26,003 GUSTO patients (1993)
• Derivation set 131 (0.5) patients with left
  bundle branch block
• Average time from onset of symptoms to ECG 120
  minutes
• Validation set 45 patients from GUSTO-2A with
  AMI and LBBB

Sgarbossa et al., NEJM, 334481, 1996
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ECG of Evolving MI with Left Bundle Branch Block

• Identified three predictive criteria
• ST segment elevation gt 1 mm concordant with QRS
• ST segment depression gt1 mm concordant with QRS
• ST segment elevationgt discordant with QRS
• How did these factors perform on the validation
  set?

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ECG of Evolving MI with LBBB

• ST elevation gt 1 mm concordant with QRS
• Sensitivity 73
• Specificity 92
• Odds ratio 25.2 (95 CI 11.6-54.7)
• ST depression gt1 mm concordant with QRS
• Sensitivity 25
• Specificity 92
• Odds ratio 6.0 (95 CI 1.9-19.3)

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ECG of Evolving MI with Left Bundle Branch Block

• ST elevation gt 5 mm discordant with QRS
• Sensitivity 26
• Specificity 92
• Odds ratio 4.3 (95 CI 1.8-10.6)
• Decision tree incorporates all three factors in
  order of predictive power

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ECG of Evolving MI with Left Bundle Branch Block

• Does the T wave go the wrong way up?
• Does the T wave go the wrong way down?
• Does the T wave/ST segment go the right way, but
  too far?
• Three yes answers 100 MI
• Three no answers 16 MI

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Probability of MI 100 92 93
88 100 66 50 16
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Right Bundle Branch Block in V1
up down
Secondary normal ST-T Wave changes
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Right Bundle Branch Block in V6
down up
Secondary normal ST-T Wave Changes
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Left Bundle Branch Block V1
down up
Secondary normal ST-T Wave changes
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Left Bundle Branch Block V6
up down
Secondary normal ST-T Wave changes
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Right Bundle Branch Block V1
up up
Primary Infarction ST-T Wave changes
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Right Bundle Branch Block V6
down down
Primary Ischemic ST-T Wave Changes
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Left Bundle Branch Block V1
down down
Primary Ischemic ST-T Wave Changes
30
Left Bundle Branch Block V6
up up
Secondary Infarction ST-T Wave Changes
31
Left Bundle Branch Block V1
gt 5 mm
too far up
Primary Infarction ST-T Wave change Exaggerated
ST Segment Elevation
32
Right Bundle Branch Block with Secondary ST-T
Wave Changes
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Left Bundle Branch Block with Secondary ST-T Wave
Changes
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Right Ventricular Paced Rhythm with LBBB Pattern
Secondary ST-T Wave Changes
35
RBBB with Anteroseptal Ischemia
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RBBB with Anteroseptal Infarction
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LBBB with Exaggerated ST Elevation
Anteroseptal/lateral Infarction
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LBBB with Lateral Infarction
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Left Bundle Branch Block with Anteroseptal
Ischemia
40
Left Bundle Branch Block
Primary ST T Wave depression
Primary STT Wave elevation
Exaggerated ST segment elevation
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Are These Criteria Valid?

• Poor performance
• 190 patients/13 with AMI
• Sensitivity 0-16
• Specificity 93-100
• Treat all LBBB not known to be old as acute MI
• Good performance
• 224 patients/45 with AMI
• Sensitivity 73 (cardiologist) vs. 67 (EP)
• Specificity 98 (both)

Li, et al., Annals EM, 36561, 2000 Sokolove, et
al., Annals EM, 36566, 2000
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ECG of Evolving MI with LBBB

• 414 ECGs with AMI and LBBB, 85 with LBBB without
  AMI
• Prevalence of findings
• Concordant ST-segment elevation 6.3
• Concordant ST-segment depression 3.1
• Discordant ST-segment elevation 19.0
• Concordant ST elevation and ST depression in
  V1-V3 were highly specific for diagnosis of AMI.

Gula LJ et al., Coron Artery Dis. 14387-93,
2003
43
ECG of LBBB Without MI

• 124 patients with LBBB and no MI
• Only 1 had primary ST segment depression
  anteriorly
• Only 1 had primary ST segment elevation
• 9 had exaggerated ST segment elevation gt 5 mm
• Sgarbossa criteria are sufficiently specific (few
  false positives)

Madias JE, et al., Clin Cardiol. 24652-5, 2001
44
ECG of Evolving MI with LBBB

• 182 patients with LBBB and acute MI
• New LBBB Sens 46, Spec 65
• Concordant ST-segment elevation or depression
  (Sgarbossa criteria)
• Specificity 100
• Positive predictive values 100
• Sensitivity for ST elevation 8
• Sensitivity for ST depression 17

Kontos MC, et al., Ann Emerg Med. 37431-8, 2001
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ECG of Evolving MI with LBBB

• Of patients with acute MI and LBBB, the LBBB was
  NEW (from their MI) in only 46.
• If we only treated NEW LBBB, wed miss treating
  54 of patients who needed it.
• Conversely, only 65 of patients with NEW LBBB
  actually had MI.
• So, if we treated everyone with new LBBB and
  chest pain wed treat 35 unnecessarily.

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Should We Treat All Patients?

• American Heart Association
• Literature not necessarily
• 35 with new LBBB and chest pain did not have an
  MI (Kontos)
• 48 with LBBB not known to be old did not have an
  MI (Edhouse)
• Sgarbossa criteria are helpful
• If present, thrombolytics indicated
• If absent, serial ECGs or catheterization

Yes!
Edhouse, et al., J Accid Emerg Med. 16331-5,
1999.
47
Take-home Messages

• You can make the diagnosis of acute myocardial
  infarction or ischemia in the face of bundle
  branch blocks or paced rhythm.
• Secondary ST-T wave changes are normal, and go in
  the opposite direction of the last portion of the
  QRS complex.
• Primary ST-T wave changes mean ischemic or
  infarction, and go in the same direction as the
  last portion of the QRS complex.

48
Take-home Messages

• Left bundle branch block that is new or not known
  to be old, in the setting of a clinical picture
  of MI, likely indicates infarction.
• Reperfusion therapy is recommended.
• Serial ECGs may clarify the situation.
• Immediate angiogram is preferred.