WBR1011

Author	[[PageAuthor::Mohamed Moubarak, M.D. [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Emergency Room
Sub Category	SubCategory::Cardiovascular
Prompt	[[Prompt::A 56 year-old female presents to ED complaining of sudden onset of dizziness, palpitation, and light headedness. These symptoms have been occurring frequently for the past week, last for few minutes, and resolve spontaneously. She has a history of hypertension, and ischemic heart disease. Her current medications are daily aspirin, metoprolol, and hydrochlorothiazide. On examination, her heart rate is 110 beat per minute and shows irregular irregularity, blood pressure is 130/80 mmHg, temperature is 37 C (98.6 F), and respiratory rate is 18/min. Her EKG shows atrial fibrillation. After controlling the ventricular rate with IV diltiazem drip, she is prescribed amiodarone for the maintenance of sinus rhythm, and warfarin as an anticoagulant. Which of the following is the most important test to order after 7 weeks of follow up?]]
Answer A	AnswerA::EKG
Answer A Explanation	[[AnswerAExp::Incorrect EKG is a vital test to follow up this case, and wouldn’t wait for 7 weeks to order it]]
Answer B	AnswerB::Echocardiography
Answer B Explanation	[[AnswerBExp::Incorrect Echocardiography is not mandatory after 7 weeks of follow up]]
Answer C	AnswerC::Platelet count
Answer C Explanation	[[AnswerCExp::Incorrect Platelet count is not mandatory to order after 7 weeks, as there is no drug affecting the platelet count]]
Answer D	AnswerD::Prothrombin time (PT)
Answer D Explanation	[[AnswerDExp::Correct Prothrombin time (PT) and INR are mandatory to order after 7 weeks, to detect the interaction effect between amiodarone and warfarin, which may lead to fatal bleeding.]]
Answer E	AnswerE::Stress test
Answer E Explanation	[[AnswerEExp::Incorrect There is no need to order stress test as the patient is already diagnosed, and does not complain from any ischemic manifestations with normal EKG.]]
Right Answer	RightAnswer::D
Explanation	[[Explanation::Amiodarone is the ant arrhythmic agent of choice that is used to treat ventricular arrhythmias and atrial fibrillation. Amiodarone augment the anticoagulant effect caused by warfarin, and results in an increase in international normalized ratio (INR) and increased risk of bleeding. The effects of interaction with amiodarone do not peak until seven weeks after the initiation of concomitant therapy. A mean reduction of 35% in the dose of warfarin, and frequent follow up of INR and prothrombin time is needed when amiodarone used with warfarin. Reference:"The incidence, magnitude, and time course of the amiodarone-warfarin interaction.", journal = Arch Intern Med, volume = 148, issue = 8, month = Aug, year = 1988, PMID = 3401099. Educational Objective: References: ]]
Approved	Approved::No
Keyword	[[WBRKeyword::Amiodarone]]
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::