Term
| Two types of ischemia/MI patterns |
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Definition
• Transmural—Q wave infarctions
• Subendocardial—non-Q wave infarctions |
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Term
| • For our purposes, the ventricles have two layers: |
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Definition
• Epicardium
• Subendocardium
• Subendocardium is the most at risk during an MI
[image] |
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Term
| blood supply of the heart pictures, arteries |
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Definition
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Term
| Transmural Ischemia and Myocardial Infarction |
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Definition
• Ischemia à necrosis
• Full thickness (+)
• Diagnosis of MI:
• Abnormal Q waves
• ST segment elevation • T wave inversion
[image] |
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Term
| What Happens Over Time for MI?, first change |
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Definition
• ST segment elevation is usually first change • “Current of injury”
• Not fully understood as to why there is elevation • ? Has to do with abnormal current flow |
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Term
| What Is Significant ST Elevation? |
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Definition
• May have variable shapes
• May be accompanied by tall, peaked,
“hyperacute” T waves
• Called “acute phase” or “injury pattern”
• Cellular injury occurs after prolonged ischemiaàCellular death |
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Term
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Definition
| tombstoning ST elevation, widowmaker, involves left mainstem artery, usually don't survive |
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Term
| What Is the “Evolving Phase” or “Ischemia Pattern”? |
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Definition
• Occurs in hours or days
• ST segments comes down/returns to(ward)
baseline
• T waves invert in leads where there was ST segment elevation |
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Term
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Definition
• Dead area of myocardium has no electrical forces moving in it
• All forces will be moving away from this area, resulting in a Q wave
• Abnormal Q wave is pathognomonic feature of a transmural infarction |
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Term
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Definition
| Q waves may appear early in the acute phase of an infarct and remain as a marker of an old infarction after the ST segment and T wave changes have resolved |
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Term
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Definition
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Term
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Definition
| hyperacute t-wave, min-hours |
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Term
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Definition
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Term
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Definition
| Q wave developing over 1-12 hours |
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Term
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Definition
| st elevation with t-wave inversion 2-5 days |
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Term
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Definition
| t-wave recovery weeks-months |
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Term
| How Can We Tell Where the MI Is Located? |
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Definition
ECG leads overlaying the area of the infarction are the leads which will show the “indicative” changes
[image] |
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Term
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Definition
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Term
| anterolaterial infarct leads |
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Definition
I, aVL- pos R
V5- neg R
V6- biphasic |
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Term
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Definition
II, III, aVF- neg R
V6- more pos R |
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Term
| What Are Reciprocal Changes? ex |
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Definition
• Changes that occur in the leads overlaying the portion of the myocardium opposite of the MI
• For ECG purposes, the anterior wall (leads V1–V6, I, and aVL) are opposite to the inferior leads (leads II, III, and aVF) |
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Term
| findings and reciprocal changes for ST elevation, T inversion, Qs both anterior and inferior lead changes chart |
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Definition
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Term
| posterior wall infarctions |
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Definition
• There are no ECG leads overlaying the posterior wall
• Use reciprocal changes
• Difficult to diagnose
• Posterior MI not uncommonly associated with anterior or lateral wall MIs |
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Term
| true posterior infarct leads |
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Definition
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Term
| What Effects Does an LBBB Have on MIs? (left bundle branch block) |
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Definition
• Masks abnormal Q waves of infarction and ST segment elevation and T wave inversion of ischemia
• LBBB gives QS waves in the right chest leads with ST segment elevation and poor R wave progression without ischemia
• Sgarbossa, et al. NEJM 334(8): 481–487, 1996. • 36% sensitivity, 96% specificity
• Predictive probability of MI
• Not a diagnostic tool |
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Term
| What About a Transmural Infarction? |
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Definition
| • In a transmural infarction there are indicative and reciprocal changes |
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Term
| what is at greatest risk for ischemia |
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Definition
• Subendocardium is at greatest risk for ischemia • Farthest away from blood supply
• Against the ventricle with higher pressure |
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Term
| curerent in subendocardial ischemia |
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Definition
| • In a subendocardial infarction the current of injury is directed inward, leading to ST segment depression |
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Term
| subendocardial injury vs transmural injury picture comparison and ekg |
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Definition
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Term
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Definition
• ST segment depression occurs within minutes to hours of the acute event, then returns to baseline after several days
• Caused by a difference in the injury current vector
• In transmural MI, the vector is directed towards the
outer layer of the heart, causing ST elevation
• In subendocardial MI, the electrical forces are directed towards the inner layer of the heart, causing ST depression |
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Term
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Definition
• T wave inversion may also appear with or without ST segment depression
• Occurs within minutes to hours and will remain inverted at least 24–48 hours
• May remain inverted indefinitely but in most cases will return to baseline
• Generally, the lead pattern in which the changes occur varies
• More diffuse than in transmural MI • Aneurysm formation is uncommon |
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Term
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Definition
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
| Massive anterior MI—ST elevation with “tombstone” morphology is present throughout the precordial (V1–6) and high lateral leads (I, aVL). Seen in proximal LAD occlusion and indicates a large territory infarction. |
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Term
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Definition
| Inferolateral MI—ST elevation in the inferior (II, III, aVF) and lateral (I, V5– 6) leads. The precordial ST elevation extends out as far as V4; however, the maximal STE is in V6. This constellation of ECG abnormalities is typically produced by occlusion of the proximal circumflex artery. |
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Definition
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