1. Scott Ewing, D.O. Cardiology Fellow August 30, 2006
Practical Electrocardiography – Myocardial Ischemia and Acute Myocardial Infarction
Scott Ewing, D.O.
Cardiology Fellow
August 30, 2006

4. Assess Initial 12-Lead ECG Findings
ST elevation or new or presumably new LBBB:
strongly suspicious for injury
ST-elevation AMI
ST depression or dynamic T-wave inversion:
strongly suspicious for ischemia
High-risk unstable angina/ non–ST-elevation AMI
Nondiagnostic ECG:
absence of changes in ST segment or T waves
Intermediate/low-risk unstable angina
Classify patients with acute ischemic chest pain

5. Current-of-injury patterns with acute ischemia
Resultant ST vector is directed toward the inner layer of the affected ventricle and the ventricular cavity. Overlying leads therefore record ST depression
(Transmural or epicardial injury), ST vector is directed outward. Overlying leads record ST elevation. Reciprocal ST depression can appear in contralateral leads.

6. Acute Ischemia / Non-Q Wave MI / Non-ST Elevation MI
Evolving ST-T changes over time without the formation of pathologic Q waves
Localization of non-Q wave MI by the particular leads showing ST-T changes is probably only valid with ST segment elevation pattern
Evolving ST-T changes may include any of the following patterns:
Convex downward ST segment depression
T wave flattening or inversion
Biphasic T wave changes
Combinations of above changes

7. Ischemic T Wave Changes

8. Ischemic T Wave Inversion

9. Ischemic ST Changes

10. Ischemic Biphasic T Wave Changes

11. Acute Ischemia - T Wave Changes

12. Acute Ischemia – ST Depression

13. Acute Ischemia – ST Depression

14. Acute Ischemia – ST Depression

15. 60-year-old Male

16. Anterior Ischemia
ECG shows sinus rhythm with ventricular ectopy, left axis deviation, consistent with left anterior fascicular block (hemiblock), and T wave inversions in V2-V5 with subtle upward bowing of the ST segments
ST-T abnormalities in I and aVL
Symmetric T wave inversions, especially with upward bowing of the ST segments is highly suggestive of ischemia in the left anterior descending distribution (LAD) in this context
Most expeditious test to order is a cardiac catheterization, which showed significant LAD (and obtuse marginal) disease

17. Elderly Male

18. Severe Ischemia
NSR at about 65 bpm with profound precordial ischemic ST segment depression, consistent with severe subendocardial ischemia and probable non-Q wave myocardial infarction
Q waves in the infero-lateral leads are consistent with prior myocardial infarction(s)
Profound ST depressions of this type usually indicate severe multivessel disease, and sometimes left main coronary disease
Patient experienced severe chest pain and was transferred from an outside facility in cardiogenic shock
En route to the cardiac catheterization laboratory, he developed refractory PEA and ventricular fibrillation

19. 84-year-old Female

20. NQWMI
Left ventricular hypertrophy (LVH) plus left atrial abnormality (LAA)
QRS axis is somewhat leftward (-7 degrees)
Although LVH alone may be associated with ST-T abnormalities (sometimes referred to as a "strain pattern"), like those in lead aVL, the prominent horizontal or downsloping ST depressions in other leads (I, II, aVF, V5, V6) here are strongly suggestive of ischemia superimposed on LVH
The patient had positive cardiac enzymes and underwent cardiac catheterization showing left main and three vessel coronary disease, followed by coronary artery bypass graft surgery.

21. Current-of-injury patterns with acute ischemia
Resultant ST vector is directed toward the inner layer of the affected ventricle and the ventricular cavity. Overlying leads therefore record ST depression
(Transmural or epicardial injury), ST vector is directed outward. Overlying leads record ST elevation. Reciprocal ST depression can appear in contralateral leads.

22. Acute Myocardial Infarction / ST Elevation MI / Q Wave MI
Most acute MI's are located in the left ventricle
In the setting of a proximal RCA occlusion, however, up to 50% may also have a component of RV infarction as well
In general, the more leads of the 12-lead ECG with MI changes (Q waves and ST elevation), the larger the infarct size and the worse the prognosis
LAD and it's branches usually supply the anterior and anterolateral walls of the LV and the anterior two-thirds of the septum
LCX and its branches usually supply the posterolateral wall of the LV
RCA supplies the RV, the inferior (diaphragmatic) and true posterior walls of the LV, and the posterior third of the septum
RCA also gives off the AV nodal coronary artery in 85-90% of individuals; in the remaining 10-15%, this artery is a branch of the LCX

23. Acute Myocardial Infarction / ST Elevation MI / Q Wave MI
Normal ECG prior to MI
Hyperacute T wave changes - increased T wave amplitude and width; may also see ST elevation
Marked ST elevation with hyperacute T wave changes (transmural injury)
Pathologic Q waves, less ST elevation, terminal T wave inversion (necrosis)
Pathologic Q waves are usually defined as duration >0.04 s or >25% of R-wave amplitude
Pathologic Q waves, T wave inversion (necrosis and fibrosis)
Pathologic Q waves, upright T waves (fibrosis)

24. Evolution of ECG Changes

25. Evolution of ECG Changes

26. Infarct - ST Elevation

27. Inferior Infarct – ST Elevation

28. Inferior Infarct – ST Elevation

29. Posterior Infarct – ST Elevation!!!

30. Old Infarct - Anterior Q Waves

31. Old Infarct - Inferior Q Waves

32. Persistent ST Changes

33. Persistent T Wave Changes

34. 34 Year Old Male With Chest Pain

35. 34-year-old male

36. Acute Anterior MI
Classic findings of acute anterior wall Q wave myocardial infarction
Reciprocal inferior ST depressions
Hyperacute T waves
Distribution of changes is consistent with a proximal LAD occlusion
Confirmed at cardiac catheterization and treated with PTCA and stenting

37. 68-year-old female

38. Acute Anterior MI Note Q waves and loss of R waves V1 - V4
ST elevation in V2 - V5/V6
Left anterior fascicular block is also present, but does not account for the loss of R wave progression
The patient had had a very recent anterior MI
Cardiac catheterization revealed 3-vessel disease with a 90% mid-LAD "culprit" lesion

39. 53-year-old female

40. Acute Lateral MI ST elevations in I and aVL
Probable reciprocal ST depressions inferiorly consistent with acute lateral MI
Remember: ST elevations like this are never reciprocal but indicate the primary region of ischemia (diagonal or circumflex lesion)
Confirmed left circumflex occlusion at catheterization

41. * 36-year-old male

42. Acute Pericarditis
Always consider myocardial infarction first when you see ST elevations
But don't forget the differential diagnosis of ST elevations
Ischemic heart disease
Pericarditis
Left bundle branch block (LBBB)
Normal ("early repolarization") variant
Two features here point to pericarditis
First, diffuseness of the ST elevations (I, II, III, aVF, V3-V6)
Second, PR depression in II, aVF, V4-V6 and PR elevation seen in aVR (attributed to subepicardial atrial injury)

43. 49-year-old male

44. Acute Pericarditis Diffuse ST segment elevations (I, II, aVF, V2-V6)
Subtle PR segment deviations (elevated in aVR and depressed in the inferolateral leads)
ST elevations are due to a ventricular current of injury from the pericardial inflammation
PR changes are due to an associated atrial current of injury
Note that the PR and ST segment vectors point in opposite directions, i.e., PR up and ST down in aVR and PR down and ST up in inferolateral leads

45. Middle aged female

46. Acute Myocardial Infarction
Marked inferior and lateral ST segment elevation
ST segment depression in anterior leads V1-V4
ST elevations (“current of injury” pattern) indicate transmural ischemia of the infero-lateral wall
ST depression most consistent with reciprocal change from the ST elevation generated by the acute posterior and lateral ischemia
Remember, acute pericarditis causes diffuse ST segment elevation (e.g., leads I, II, III, aVL, aVF, and the precordial leads)
Reciprocal ST depressions of the type seen here (V1-V4), are never a feature of pericarditis alone
Cardiac catheterization revealed acute occlusion of a dominant left circumflex coronary artery (along with occlusion of a smaller RCA)

47. 52-year-old male

48. ST Elevation Myocardial Infarction
Slight inferior ST elevation with T wave inversion
Minimal reciprocal ST depression in aVL
Relatively low limb lead voltage makes these findings more subtle