KINE 639 - Dr. Green

1
KINE 639 - Dr. Green Section 7 Ischemia
Infarction Ischemia Infarction Reading in
Conover pages 332-365
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Ischemia Infarction

• Ischemia at rest non-specific T and ST
  changes
• changes in the T-wave or the ST segment that are
  out of place
• normally, the T-wave and the QRS complex have
  similar polarity
• T-wave flattening
• T-wave inversion
• ST-segment scooping
• ST-segment depression

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Ischemia Infarction
Inferior Ischemia in a 42 year old male while at
rest
I
II
III
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Ischemia Infarction
Anteriolateral Ischemia in a 67 year old female
while at rest
V1
V4
V2
V5
V3
V6
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Ischemia Infarction

• Ischemia during exercise ST-segment
  depression
• usually indicative of subendocardial ischemia
• location of ischemia does not always correspond
  to the leads
• in which it is seen

Baseline
Quantity or depth of ST-segment
depression
J-point
.08 seconds
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Ischemia Infarction

• Types of ST-segment depression

UPSLOPING very nonspecific for the diagnosis of
ischemia. Associated with a lot of false
positive exercise tests.
HORIZONTAL likely associated with ischemia.
DOWNSLOPING almost certainly associated with an
ischemic myocardium
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Ischemia Infarction
Ischemia during exercise (horizontal-upsloping)
ST depression in lateral leads
8
An example of inferioseptal ischemia. Note stress
defects from 6 oclock to 9 oclock in the short
axis view and horizontal long axis view that
redistributes at rest.
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Ischemia Infarction

• Myocardial Infarction Pathology
• CA plaque is injured, ulcerates, or is ruptured
• r platelet aggregation, fibrin deposition,
  spasm (clot formation r occlusion)
• cells robbed of O2 begin relying on anaerobic
  glycolysis
• after 10 seconds, fuel is depleted and cells
  become stunned
• stunned cells unable to participate in
  contraction
• reversible if O2 supply is restored
• if O2 is not restored r INFARCTION (MI)
• cells become necrotic electrically inactive
• wall motion problems
• Emergency Treatment for infarction
• arrives at ER within 12 hours of symptoms onset
• Critical point The earlier ER arrival the
  better
• ER arrival within 60-90 minutes necessary
• for the success of most interventions
• Drugs
• aspirin, b blockers, nitro, morphine
• PTCA (best results)
• Fibrinolytic therapy

left anterior oblique cross section of LV
sub epicardial vessels
blockage
sub endocardial vessels
Transmural MI
SubendocardialMI
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Ischemia Infarction

• Indications of an acute infarction
• Usually no ECG changes are seen in the first few
  minutes after occlusion
• Appearance of tall narrow T-waves or ST-segment
  elevation
• 5 to 30 minutes post occlusion
• A few hours later, the T-waves invert (ischemia)
  
• in an MI, the T-wave inversion is symmetrical an
  may persist for years
• inverted T-waves without other indications are
  not diagnostic of an MI
• ST-segment elevation indication of injury
  (although it may be reversible)
• ST-elevation may also indicate transmural
  ischemia
• usually the first definite sign of an infarction
• may or may not be accompanied by T-wave
  inversion
• 1mm or more in limb leads or 2mm or more in
  precordial leads
• differentiate between early repolarization or
  J-point elevation
• the larger the ischemic area, the greater the
  ST displacement
• ST elevation persisting for more than a few
  hours may indicate ventricular aneurysm
• ST depression may be seen in reciprocal leads.

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Ischemia Infarction
Acute anteriolateral MI
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Ischemia Infarction

• Biomarkers in an MI

50
Myoglobin
Cardiac Troponin
20
CK-MB
10
Cardiac Troponin after unstable angina
5
Multiples of the AMI cutoff Limit
2
AMI decision limit
1
Upper normal limit
0
0
1
2
3
4
5
6
7
8
Days after MI Onset
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Ischemia Infarction

• Indications of an old or resolved infarction
• Significant Q-waves where they dont belong
• (nonsignificant Qs may be found in V1 alone,
  III alone, and AVR)
• These Qs represent necrotic tissue r main
  vector directed away from that lead
• In general, for Qs to be significant
• must be at least .03 - .04 seconds wide
• must be at least 1/3rd of the height of the
  R-wave in the QRS complex
• must be new (not seen in a previous tracing)
• in most cases, they must be in more than one
  lead
• Speculating as to the location of the infarct
• Significant Qs in II, III, AVF old inferior
  infarction
• Significant Qs in I, V1, V2, V3 old anterior
  infarction
• Significant Qs in V4, V5, V6 old lateral
  infarction
• Infaract criteria (as well as all other voltage
  related diagnosis) may be invalid in the
  presence of BBB

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Ischemia Infarction
Old Inferior MI