Review Question - QID 109088

The patient in this vignette presents with chest pain and ECG findings suggestive of a lateral ST elevation myocardial infarction (STEMI). Clopidogrel is an anti-platelet ADP receptor inhibitor that is an alternative to aspirin in patients undergoing stent placement for STEMIs.

Coronary stenting is an intervention used to restore coronary flow to ischemic myocardium. Antiplatelet agents are necessary following any stent procedure to prevent clot formation over the stent. Although aspirin is considered the first-line therapy for this purpose, clopidogrel is an alternative option in patients who cannot take aspirin. Clopidogrel irreversibly blocks ADP receptors on platelets, thereby preventing ADP-mediated expression of glycoprotein IIb/IIIa on the platelet surface. Notably, other interventions that would take place in this patient would be a heparin drip prior to catheterization and stent placement.

Incorrect Answers:
Answer 1: Thrombin (factor IIa) inhibitors such as lepirudin and bivvalrudin are anti-coagulant medications. They are used as alternatives to heparin during heparin-induced thrombocytopenia which presents with increased coagulability and decreased platelets after heparin administration secondary to heparin-platelet factor IV immunogenic complexes.

Answer 2: Phosphodiesterase activators are not a mechanism of an antiplatelet agent. Phosphodiesterase (and its activators) breaks down cAMP in platelets and promotes platelet aggregation. Phosphodiesterase inhibitors such as cilostazol and dipyridamole, on the other hand, are anti-platelet agents used in the treatment of claudication, stroke prophylaxis, and stable angina and could also be used as an anti-platelet medication in this aspirin-allergic patient.

Answer 3: Warfarin is a vitamin K epoxide reductase inhibitor that is used extensively for chronic anticoagulation. It is not used in MI patients given its slow onset of action but could be used for long-term anticoagulation in atrial fibrillation.

Answer 5: Cyclooxygenase activator is not a mechanism of an anti-platelet agent. Aspirin acetylates and irreversibly inhibits cyclooxygenase (COX) in platelets, preventing the conversion of arachidonic acid to thromboxane A2. Thromboxane A2 normally activates platelets for clot formation. Aspirin is widely used as a prophylactic agent against MI and stroke though may be less desirable in this aspirin-allergic patient.

Bullet Summary:
Clopidogrel and ticlopidine, ADP receptor inhibitors, are used in patients with vascular stents and as prophylactic agents in patients at high risk for MI and stroke.