《Slide 23.》Myocardial infarction, Heart

A. Brief Descriptions：

1. Myocardial infarction is the most important form of ischemic heart disease.

2. Pathogenesis: coronary arterial occlusion.

3. Risk factors: atherosclerosis, old age, diabetes mellitus, hypertension, cigarette smoking, genetic hypercholesterolemia, ….

B. Gross Findings：

1. All infarction tend to forming wedge shaped occluded vessel at apex and the periphery of the organ forming the base.

2. Spongy and cyanotic in red infarct at first.

3. The margin of both type become progressively better defined in the course of few days.

C. Micro Findings：

1. Irregular fibrous bundles replaced the cardiac muscle as chronic myocardial infarction.

2. Interrupted and separated cardiac muscle by fibrous tissue.

3. Proliferation of capillary in the interstitium.

D. Others:

1. The coagulative necrosis may not detectable for the first 4~8 hrs.

2. Sequential changes in myocardial infarction:

time	gross	light microscopy
1 ~ 4 hrs	none	none
4 ~ 12 hrs	none	begin coagulative necrosis, neutrophil infiltrates ; edema, hemorrhage.
18 ~ 24 hrs	pallor	continuing coagulation necrosis marginal contraction band necrosis
24 ~ 72 hrs	pallor, sometimes hyperemia	loss of nuclei and striation heavy infiltration of neutrophils
3 ~ 7 days	hyperemic border central yellow-brown	disintegration of dead myofibers macrophages present onset of marginal fibrovascular response
10 days	red-brown & depressed yellow & soft vascularized margins	well-develop necrotic changes prominent fibrovascular reaction in margin
7th weeks	scarring	fibrotic

　

E. Reference：

1. Robbins Pathologic Basis of Disease, 6^th ed.  P.71.

　

 

 

【 Fig. 23-1 (LP)】Irregular fibrous bundles (left) replaced the cardiac muscles.Granulation tissue (right) with a rich vascular network and early collagen deposition.

　

 

 

【 Fig. 23-2 (HP)】Fibrous bundles arrange in a parallel fashion with capillaries and minimal inflammation; note separated and interrupted cardiac muscles.

　

 

 

【 Fig. 23-3 (HP)】Fibrous bundles arrange in a parallel fashion with capillaries and minimal inflammation; note separated and interrupted cardiac muscles.