Your 69-year-old patient awoke with severe dyspnea and is only able to talk in two- to three-word bursts. Her skin is cool, pale, and diaphoretic with labored respirations at 30 with an SpOβ of 80% on room air. She has audible wheezes and rales with pitting edema peripherally. She has an irregular heart rate of 100 to 110 bpm, and her ECG shows A-fib with no obvious pathological ST elevation or depression. Her blood pressure is 160/100 in an upright sitting position. She has a history of COPD, hypertension, and congestive heart failure.
Which of the following would be a first-line medication for this patient?