Why is aspirin used in myocardial infarction?

[scilearner]

Hello,

 

I'm simply confused how effective is giving aspirin in various cardiac disorder? Ok someone develops severe chest pain, presents to hospital within 3 hours due to MI?Is there any use in giving aspirin. I know aspirin disaggregates platelets, and this is primary haemostasis. Now within 3 hours I believe primary haemostasis is already done, so is their any point in giving aspirin. What I'm basically asking is how long does primary and secondary haemostasis take and also lets say a full thrombus was formed then is the only choice available is to lyse it with streptokinase, or does aspirin have an effect even after a full thrombus is formed. Then having said all that and if they are only true only use I can see of aspirin is prophylaxis in cardiac disorders or very early MI. Thanks

Edited May 27, 2013 by scilearner

[EdEarl]

Aspirin thins blood, which allows more to flow through small openings, as restrictions in arteries and veins caused by plaque.

[sam1123]

It's in a class of drugs called COX inhibitors, they block a certain molecule that is part of the clotting cascade, therefore reducing the ability of blood to clot. This can help reduce ischaemia (reduced blood flow) in a myocardial infarction, which when prolonged can cause the irreversible death of cardiac myocytes.

 

As far as I know aspirin cannot break clots, but only prevents them from forming. If substantial clotting has already taken place then a fibrinolytic drug like streptokinase (a compound found in Streptococci bacteria) or urokinase may be given, but because these break clots they have a more direct action than the preventative action of aspirin, therefore you'd need to be totally sure of a patient's circumstances before giving it, you don't want to cause a bleed.

 

Essentially aspirin has a largely preventative role, hence why it is recommended that you give someone an aspirin to chew slowly after they have had a heart attack/myocardial infarction. I'd say definitely the sooner you administer it, the better.