ABSTRACT
A stat dose of 300 mg aspirin is the correct figure. Low-dose (75 mg) aspirin is used for long-term prevention. ACS is the title given to a collection of cardiac diseases that all share the same atherosclerotic aetiology. ST-elevated MI, non-ST-elevated MI and unstable angina are all caused by stenosed coronary arteries starving the myocardium of oxygen (angina), leading to hypoxic cell death (myocardial infarction). Unstable angina occurs on the cusp of these phenomena, when a rest is no longer adequate to replenish the myocardium with oxygen. Acute coronary stenoses are usually caused by intimal plaque rupture leading to an intraluminal thrombus. Aspirin, clopidogrel and heparin aim to prevent platelets binding and therefore to arrest thrombus growth and dissolve the thrombus. Aspirin can cause stomach ulcers and so, in order to balance risks and benefits, low-dose aspirin is given long term; a higher dose (300 mg) is given acutely. Statins prophylactically lower serum cholesterol, and so it is thought to reduce plaque formation in the first place. ACE inhibitors and beta-blockers reduce afterload and heart rate, so the heart does not have to work as hard – this lowers its oxygen demand, hopefully enough to prevent hypoxic damage.
