A 62 year old male with a history of hypertension, diabetes, rheumatoid arthritis and prior mechanical aortic valve replacement, presents to the emergency department with fevers for 3 days. He denies any chest pains or shortness of breath. His medications include lisinopril, hydrochlorothiazide, aspirin, and coumadin. His temperature is 38.4 C, blood pressure is 160/60, heart rate 100, respirations 20, and oxygen saturation 99% on room air. Physical examination reveals normal lung sounds, a II/IV early diastolic decrescendo murmur at the left lower sternal border, and a very soft S1 heart sound. Laboratory studies reveal a white blood cell count of 15 thousand and an ESR of 110. A portion of his ECG is below. Which of the following is the most approtriate test to obtain at this time?
A. Coronary angiography
B. Transthoracic echocardiogram
C. Transesophageal echocardiogram
D. Cardiac magnetic resonence imaging