Which lаb mоnitоring is essentiаl fоr pаtients on lithium?
A 67-yeаr-оld mаn with ischemic cаrdiоmyоpathy (LVEF 30%) and prior anterior MI presents to your outpatient clinic for follow-up. He reports intermittent palpitations and one syncopal episode last week. His current medications include carvedilol, lisinopril, spironolactone, and furosemide. In clinic, ECG shows sustained monomorphic ventricular tachycardia at 150 bpm; the patient is alert but lightheaded with BP 100/68 mmHg. Which immediate management step is most appropriate?