A 58-year-old man from Delhi presents with a 3-week history of fever, malaise, and progressive dyspnea. On examination, he has a blood pressure of 165/95 mmHg, a new diastolic murmur, and splinter hemorrhages on fingernails. Laboratory investigations show elevated inflammatory markers (ESR 92 mm/h, CRP 8.5 mg/dL) and mild renal impairment (creatinine 1.8 mg/dL). Urinalysis shows hematuria with RBC casts. Transthoracic echocardiography reveals vegetations on the aortic valve. Blood cultures are pending. What is the most appropriate immediate next step in management?