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{{WBRQuestion
|QuestionAuthor=Gerald Chi
|ExamType=USMLE Step 1
|MainCategory=Pathology
|SubCategory=Cardiology
|MainCategory=Pathology
|SubCategory=Cardiology
|MainCategory=Pathology
|SubCategory=Cardiology
|MainCategory=Pathology
|MainCategory=Pathology
|SubCategory=Cardiology
|MainCategory=Pathology
|SubCategory=Cardiology
|MainCategory=Pathology
|SubCategory=Cardiology
|MainCategory=Pathology
|SubCategory=Cardiology
|MainCategory=Pathology
|MainCategory=Pathology
|SubCategory=Cardiology
|Prompt=A 75-year-old female presents with an acute onset chest discomfort when she was walking her dog. It has lasted for more than 30 minutes and is worsened by increased physical activity, relieved partially by resting, without response to sublingual nitroglycerin. She reports cold sweating and mild shortness of breath. Her past history includes diabetes mellitus, hypertension, and dyslipidemia. Her temperature is 37.5, heart rate 115 beats per minute, blood pressure 90/65. Electrocardiogram showed ST elevation in lead I, aVL and V5-6. Which of the following events is most likely to underlie her clinical presentation?
|Explanation=The patient is likely to have acute transmural myocardial infarction of the lateral wall, as evidenced by the ECG changes. Unstable angina is suggested by the features of her chest pain as well as hemodynamic instability.
|AnswerA=Atheromatous plaque with 80% stenosis of the lumen without thrombus

|AnswerAExp='''Incorrect'''<BR> A lesion obstructing more than 75% of the lumen would tend to produce symptoms of stable angina.
|AnswerB=Diffuse coronary artery vasospasm causing flow limitation is incorrect

|AnswerBExp='''Incorrect'''<BR>Prinzmetal angina is caused by coronary vasospasm due to contraction of the vascular smooth muscle rather than by atherosclerosis directly. It occurs more commonly in younger women and typically manifests as clustered angina that occurs at rest rather than on exertion. Although approximately two-thirds of patients have concurrent atherosclerosis of a major coronary artery, this is often mild or not in proportion to the degree of symptoms. ECG changes may only be evident while the patient is experiencing an attack. Prinzmetal angina generally responds to calcium channel blockers.

|AnswerC=Ruptured atheroma with fully obstructive thrombus

|AnswerCExp='''Correct'''<BR>The patient is likely to have acute transmural myocardial infarction of the lateral wall, as evidenced by the ECG changes.

|AnswerD=Calcification and thickening of the coronary intima

|AnswerDExp='''Incorrect'''<BR>Although fibrocalcific plaque with thickening of the coronary intima may be associated with nonocclusive thrombus, it does not typically cause symptoms of unstable angina
|AnswerE=Dissection of the coronary wall with intraluminal flap

|AnswerEExp='''Incorrect'''<BR>Coronary artery dissection is most likely associated with percutaneous coronary interventions and is a rare cause of acute coronary syndrome and sudden death.
|RightAnswer=C
|Approved=No
}}