<prompt> Aspirin is used in the prophylaxis of myocardial infarction because it results in:Inhibition of thromboxane synthetaseInhibition of cyclooxygenaseDecreased serum lipidsCoronary steal phenomenon  <response>: Aspirin acts as an antiplatelet drug in MI. It inhibits cox enzyme and thus reduces the synthesis of TXA2. However it has no effect on the enzyme, thromboxane synthetase. Therefore, answer here is the inhibition of cox. 