A 62-year-old man with a history of hypertension, diabetes, rheumatoid arthritis and prior mechanical aortic valve replacement, presents to the emergency department with fever lasting 3 days. He denies any chest pain or shortness of breath. His medications include lisinopril, hydrochlorothiazide, aspirin and coumadin. His temperature is 38.4 °C, blood pressure is 160/60 mmHg, heart rate is 100 bpm, respirations 20, and oxygen saturation is 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 15,000 and an ESR of 110. A portion of his ECG is below. Which of the following is the most appropriate test to obtain at this time?
A. Coronary angiography
B. Transthoracic echocardiogram
C. Transesophageal echocardiogram
D. Cardiac magnetic resonance imaging