Evolution of MI

Question 1

0-4 Hrs

Answer 1

Risk of Arrhythmia, CHF Exacerbation and Cardiogenic Shock (inability to maintain flow = Ischemic Organ Damage)

Question 2

4-24 Hr Gross Findings:

Answer 2

• Occluded Artery, Infarct

- Dark Mottling: Pales with tetrazolium stain

Question 3

4-12 HR LM Findings:

Answer 3

• Early Coagulative Necrosis, Edema, Hemorrhage, and Wavy Fibers
• Nucleus Removal in Dead Myocytes w/ HyperEOSINOPHILIA

Question 4

4-24 Hr Risk

Answer 4

Arrhythmia

Question 5

12-24 Hr LM Findings:

Answer 5

• Contraction Bands from reperfusion injury due to calcium overload and hypertetanic contration.
• Release of Necrotic Cell Content into blood
• Beginning of NEUTROPHIL Migration

Question 6

1-3 Days Gross Findings

Answer 6

Hyperemia

Question 7

1-3 Days LM Findings

Answer 7

• Extensive Coagulative Necrosis

- Tissue surrounding infarct shows acute inflammation and NEUTROPHIL migration.

Question 8

1-3 Days Risks

Answer 8

• Fibrinous Pericarditis from Transmural Infarction presenting with chest pain and friction rubs.

Question 9

3-14 Days Gross Findings

Answer 9

• Hyperemic Border; central yellow-brown softening - maximally yellow and soft by 10 days
• Yellow Pallor from WBCs

Question 10

3-14 Days LM Findings

Answer 10

• Macrophage Infiltration followed by granulation tissue at the margins

Question 11

3-14 Days Risks

Answer 11

• Free wall rupture leading to tamponade
• Papillary muscle rupture leading to insufficiency
• Ventricular Aneurysm
• Interventricular Septal Rupture due to macrophages that have degraded important structural components.

Question 12

2 weeks to several months Gross Findings

Answer 12

• Recanalized artery, Gray-white color, and Dense, Type I Collagen

Question 13

2 weeks to several months LM Findings

Answer 13

Contracted, Complete Scar

Question 14

2 weeks to several months Risks

Answer 14

Dressler’s Syndrome, Aneurysm, or Mural Thrombus

Question 15

Dressler’s Syndrome

Answer 15

Autoimmune Pericarditis 6-8 weeks after MI