Free NBME Shelf Exam Sample Questions
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Your First Free NBME Sample Question
A 35-year-old male presents to the emergency department with rapidly progressive dyspnea, orthopnea, paroxysmal nocturnal dyspnea, and peripheral edema over the last 2 days. Prior to the current complaints, he has been experiencing fevers, malaise, and anorexia for one week. The patient had no known prior medical problems. There is no known family history of heart disease. He does report a significant history of intravenous drug use.
Vital signs reveal a blood pressure of 150/80 mmHg, heart rate of 105/min, respiratory rate of 25/min, oxygen saturation of 96% on room air, and temperature of 38.9°C (102°F). Physical examination reveals distended jugular veins bilaterally and clear lungs bilaterally. A new holosystolic cardiac murmur at the left lower sternal border is observed. There is pitting pedal edema extending into his mid-thigh. Blood cultures over the next 2 days grow Staphylococcus aureus.
The most accurate diagnostic test to confirm this patient’s diagnosis is
A. computed tomography scan of the chest
B. left-sided cardiac catheterization
D. transesophageal echocardiogram of the heart
E. transthoracic echocardiogram of the heart
Answer and Explanation
The patient is presenting with signs of decompensated heart failure, which is a result of infective endocarditis. Transesophageal echocardiogram (TEE) is the diagnostic test of choice in a patient with a high probability of endocarditis. TEE has a 90% sensitivity for detecting vegetation. This patient is at high risk of tricuspid endocarditis given his intravenous drug use. Staphylococcus aureus (S. aureus) is a common skin pathogen and is seen often with intravenous drug use. In fact, S. aureus is responsible for 80-90% of tricuspid valve endocarditis.
Patients with infective endocarditis may initially experience nonspecific symptoms such as fevers, malaise, and anorexia, as seen in this patient. As the vegetation grows on the affected valve, the patient will develop signs and symptoms of heart failure, which is a result of the insufficient valve. Embolization to the lungs can result in further respiratory decompensation in right-sided endocarditis. Left-sided endocarditis findings include splinter hemorrhages, which are linear emboli under the nails, Osler nodes that are painful raised lesions on the palms and soles, and Janeway lesions, which are painless erythematous lesions on the palms and soles. A fundoscopic exam may further reveal Roth spots, which are exudative lesions in the retina.
The image below demonstrates a transesophageal echocardiogram of a patient with tricuspid valve endocarditis:
Did you get it right? The correct answer is: D
Incorrect Answer Explanations
Answer A: CT scans can be useful in detecting pulmonary embolization, which is a consequence of infective endocarditis, although this is not the best test at identifying valvular vegetation. The most accurate diagnostic test is a TEE.
Answer B: Patients with acute coronary syndrome, refractory stable angina, and new cardiomyopathy may benefit from left heart catheterization. This is a patient presenting with a history consistent with tricuspid valve endocarditis and right-sided heart failure as a result of valve incompetence. This is not uncommon to see in a patient with tricuspid valve endocarditis and significant valvular regurgitation. The patient is young and has no other risk factors for early coronary artery disease. Cardiac catheterization would not be useful in this situation.
Answer C: Electrocardiograms are also nondiagnostic in infective endocarditis. New conduction abnormalities can result with extension of the infection into the myocardium, and embolization to the coronary vessels can cause myocardial ischemia, although the above case is not consistent with this presentation. Electrocardiogram is not sensitive or specific to make the diagnosis of infective endocarditis.
Answer E: A transthoracic echocardiogram (TTE) can be useful with the diagnosis of valvular vegetations in patients with endocarditis. It is important to realize that TTE has a sensitivity of only 55%-65%. In a patient with high probability, a cardiologist may often skip directly to a TEE as a negative TTE does not exclude infective endocarditis. However, which is the most accurate diagnostic test? As TEE has the higher sensitivity and specificity for endocarditis, it is the most accurate test.
Bottom Line: A transesophageal echocardiogram is the most accurate diagnostic test for infective endocarditis with a sensitivity of 90%, while transthoracic echocardiogram has a sensitivity of only 55%-65%.
In clinical practice, you will commonly see a transthoracic echocardiogram (TTE) performed prior to a transesophageal echocardiogram (TEE), although this is not a cost-effective method of diagnosing endocarditis, as a negative TTE would then require a TEE to be performed. The downside of a TEE includes a higher risk for the patient as the procedure requires sedation and is more invasive compared to a TTE.
For more information, see:
Role of Echocardiography in Infective Endocarditis on UpToDate
Papadakis M, McPhee SJ, Rabow MW. CURRENT Medical Diagnosis and Treatment 2014. McGraw Hill Professional; 2013: pp 1387-1390.
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