Unstable angina

A 60-year-old woman presents to the emergency room with chest pain that started 20 minutes ago while watching television at home. The pain is substernal and squeezing in nature. She rates the pain as 6/10 and admits to having similar pain in the past with exertion. Her past medical history is significant for diabetes mellitus that is controlled with metformin. The physical examination is unremarkable. An electrocardiogram (ECG) shows ST-segment depression in the lateral leads. She is started on aspirin, nitroglycerin, metoprolol, unfractionated heparin, and insulin. She is asked not to take metformin while at the hospital. Three sets of cardiac enzymes are negative. Lab results are given below: Serum glucose 88 mg/dL Sodium 142 mEq/L Potassium 3.9 mEq/L Chloride 101 mEq/L Serum creatinine 1.2 mg/dL Blood urea nitrogen 22 mg/dL Cholesterol, total 170 mg/dL HDL-cholesterol 40 mg/dL LDL-cholesterol 80 mg/dL Triglycerides 170 mg/dL Hematocrit 38% Hemoglobin 13 g/dL Leucocyte count 7,500/mm3 Platelet count 185,000 /mm3 Activated partial thromboplastin time (aPTT) 30 seconds Prothrombin time (PT) 12 seconds Urinalysis Glucose negative Ketones negative Leucocytes negative Nitrites negative Red blood cells (RBC) negative Casts negative An echocardiogram reveals left ventricular wall motion abnormalities. With the pain subsiding, she was admitted and the medications were continued. A coronary angiography is planned in 4 days. In addition to regular blood glucose testing, which of the following should be closely monitored in this patient?

A 57-year-old man is brought to the emergency department for crushing substernal chest pain at rest for the past 2 hours. The pain began gradually while he was having an argument with his wife and is now severe. He does not take any medications. He has smoked 1 pack of cigarettes daily for 35 years. He is diaphoretic. His temperature is 37.1°C (98.8°F), pulse is 110/min, respirations are 21/min, and blood pressure is 115/65 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 97%. Cardiac examination shows an S4 gallop. The lungs are clear to auscultation. An ECG is shown. Which of the following is the most likely underlying cause of this patient's condition?