Review Question - QID 210472

A 60-year-old man visits his primary care doctor after being discharged from the hospital 3 weeks ago. He presented to the hospital with chest pain and was found to have ST elevations in leads I, aVL, and V6. He underwent cardiac catheterization with balloon angioplasty and was discharged on appropriate medications. At this visit, he has been feeling deconditioned. He is not able to jog his usual 3 miles and feels exhausted after walking upstairs. He denies chest pain. His temperature is 98.6°F (37°C), blood pressure is 101/62 mmHg, pulse is 59/min, and respirations are 18/min. His cardiac exam is notable for a 2/6 early systolic murmur at the left upper sternal border. He describes mild discomfort with palpation of his epigastrium. The remainder of his exam is unremarkable. His laboratory workup is shown below:

Hemoglobin: 8 g/dL
Hematocrit: 25 %
Leukocyte count: 11,000/mm^3 with normal differential
Platelet count: 400,000/mm^3

Serum:
Na+: 136 mEq/L
Cl-: 103 mEq/L
K+: 3.8 mEq/L
HCO3-: 25 mEq/L
BUN: 19 mg/dL
Glucose: 89 mg/dL
Creatinine: 1.1 mg/dL

Which medication is most likely contributing to this patient's current presentation?