USMLE Step 3 Question of the Week #494

494.  A 45 year old man with a 20-year history of tobacco use presents to the emergency department after having repeated episodes of sharp, stabbing substernal pain with a dry, hacking cough over the last 2-3 days. The episodes last between 5-10 seconds. He first noticed them several days ago.They were not brought on by exertion and they did not improve with rest. He denies fever, shortness of breath, or tachypnea otherwise. He denies any recent sick contacts. The patient’s temperature is 99.2, heart rate is 72, blood pressure is 143/77. Cardiac exam reveals reveals regular rate and rhythm. There are no murmurs, rubs, or gallops. There are scant crackles throughout the lung fields. Laboratory findings are shown below:

WBC (x 10^3 cells/mL): 10.2
Hemoglobin (g/dL): 13.8
Hematocrit (%): 43.4
RBC (x 10^6/mL): 4.9
RDW (%): 13.2
MCV (fL/cell): 97
MCH (pg/cell): 31
MCHC (%): 36
Platelets (x 10^3): 310

Sodium (mEq/L): 141
Potassium (mEq/L): 4.2
Chloride (mEq/L): 105
Bicarbonate (mEq/L): 19
Creatinine (mg/dL): 1.1
Blood Urea Nitrogen (mg/dL): 23
Glucose, fasting (mg/dl): 78
Calcium (g/dL): 9.3
Calcium, ionized (mEq/L): 2.3

What is the best next diagnostic step?

A. Respiratory viral panel


C. Echocardiogram

D. Troponins



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