WBR0754

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 60-year-old man, with a past medical history of uncontrolled type 2 diabetes mellitus, hypertension, and dyslipidemia, presents to the emergency department (ED) with acute-onset chest pain. Following appropriate work-up, he is diagnosed with ST-segment elevation myocardial infarction (STEMI) and undergoes cardiac catheterization with stent placement. The physician advises him to start chronic therapy for secondary prevention. Six months later, the patient returns to the ED with complaints of abdominal pain and dark stools. He is then diagnosed with GI bleeding due to daily aspirin intake. The patient's lab findings most likely reveal which of the following set of lab values? ]]
Answer A	AnswerA::A
Answer A Explanation	AnswerAExp::Patients receiving aspirin do not typically have prolonged PT.
Answer B	AnswerB::B
Answer B Explanation	AnswerBExp::Patients receiving aspirin typically have a prolonged bleeding time with normal PT, PTT, and platelet counts. Aspirin is associated with platelet dysfunction without affecting the actual platelet count.
Answer C	AnswerC::C
Answer C Explanation	AnswerCExp::This shows normal lab values. Patients with aspirin typically have a prolonged bleeding time.
Answer D	AnswerD::D
Answer D Explanation	AnswerDExp::Patients receiving aspirin do not usually have low platelet counts. Aspirin is associated with platelet dysfunction without affecting the actual platelet count.
Answer E	AnswerE::E
Answer E Explanation	AnswerEExp::Bleeding time in patients receiving aspirin is usually prolonged, and platelet counts are usually within the normal range.
Right Answer	RightAnswer::B
Explanation	[[Explanation::Following cardiac catheterization and stent placement, patients are usually prescribed dual antiplatelet therapy (DAPT). With drug-eluting stents (DES), patients are usually prescribed clopidogrel ideally for 12 months along with life-long aspirin therapy. In contrast, patients who receive bare metal stents receive a shorter duration of dual antiplatelet therapy, where clopidogrel administration is limited to only one month (while aspirin is still continued for life). While drug-eluting stents are associated with a reduced risk of stent thrombosis, the limited duration of dual antiplatelet therapy with bare metal stents may be beneficial among patients who are at very high risk of bleeding, such as those alreay receiving other forms of anticoagulation for other diseases (e.g. patients with atrial fibrillation who are already receiving warfarin therapy). Accordingly, limited antiplatelet therapy with clopidogrel is associated with a reduced risk of bleeding among these patients. To date, aspirin is indicated in all patients for the secondary prevention of acute coronary syndromes (ACS), which includes STEMI, NSTEMI, and unstable angina. Aspirin is an irreversible inhibitor of cyclooxygenase (COX1 and COX2) that acts by the process of covalent acetylation. It reduces thromboxane A2 synthesis and prolongs bleeding time, without affecting the prothrombin time (PT) or partial thromboplastin time (PTT). Platelet dysfunction with aspirin therapy is described as functional, i.e. there is no actual decrease in the numbers of platelet count, but patients have a reduced platelet function and are thus at high risk of bleeding. Recently and with the introduction of novel oral factor Xa anticoagulants (NOACs), a novel "dual pathway" approach (thrombin inhibition by factor Xa inhibitors along with platelet inhibition) is currently being evaluated for the secondary prevention of ACS and may replace the traditional "dual antiplatelet" approach (aspirin plus thienopyridine). Educational Objective: Patients receiving aspirin typically have a prolonged bleeding time with normal PT, PTT, and platelet counts. Aspirin is associated with platelet dysfunction without affecting the actual platelet count. References: First Aid 2014 page 439]]
Approved	Approved::No
Keyword	WBRKeyword::Aspirin, WBRKeyword::Platelets, WBRKeyword::Clopidogrel, WBRKeyword::Drug-eluting stent, WBRKeyword::DES, WBRKeyword::Bare metal stent, WBRKeyword::Cardiac catheterization, WBRKeyword::STEMI, WBRKeyword::MI, WBRKeyword::ACS, WBRKeyword::Dual antiplatelet therapy, WBRKeyword::Dual pathway therapy, WBRKeyword::Factor Xa inhibitor, WBRKeyword::NOAC, WBRKeyword::Bleeding time, WBRKeyword::PT, WBRKeyword::PTT, WBRKeyword::Bleed, WBRKeyword::Adverse reaction, WBRKeyword::Adverse event, WBRKeyword::Adverse effect
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::