Q. In the initial phase of infarction,why subendocardial necrosis occurs first?

[sgsh]

Q. In the pathoma and other texts , it is mentioned that "In the initial phase of infarction, subendocardial necrosis occurs". I was thinking that below (sub-) endocardium is myocardium only.So in this sense, subendocardium=myocardium. Then why not, it is called myocardial necrosis rather than saying subendocardial necrosis ?

Next, Since Endocardium is the most distal portion of the heart supplied by the coronary artery, endocardium itself should be necrosed first rather than subendocarium,isn't it so??? then why subendocardial necrosis occurs first? If anybody is clear about this,can u pls explain . Thanks.

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[Keto]

Hi


most of the time... "subendocardium" just describes the area under the endocardium (subendocardial muscle), which is at greatest risk.

Endocardium itself can survive, as it can get some O2 directly from the blood in the ventricles and in addition it doesn't need as much O2 as the contracting myocytes (that's how I always thought about it... but please correct me...).

Endocardium can become necrotic. In that case, it detaches and is swept away in the bloodstream leaving an open area, where thrombi can be formed.

Take a look at this picture:

Notice, how a rim of endocard and also a thin rim of viable muscle survived in this transmural infarction.

What do you think? Does this make sense?

Have a great day.

 

[sgsh]

Thanks a lot keto for illustrating answer with nice picture. Your answer makes a lot of sense.

I too thought about it for a while and came up with few points which I want to share (But, pls correct me if I am wrong).

- In myocardial infarction/ischemia, when we talk about subendocardial or transmural infarction, it must refers to- the layer of myocardium only. That is why, we hardly use the terms, "epicardial infarction", or "Endocardial infarction".

subendocardial infarction -( layer below the endocardium = myocardium). So, subendocardial infarct refers to " only myocardium furthest from the coronary artery is infarcted"

transmural infarction-full thickness of the myocardium is infarcted.

 

[Keto]

Yes, totally agree with this.