A 64-year-old man presents with increased shortness of breath. He has a past history of chronic obstructive pulmonary disease (COPD) and recently developed increased cough and sputum production but no fever or chills. He appears in mild respiratory distress, respirations are 26/min, pulse 120 beats/min, blood pressure 145/84 mm Hg, and oxygen saturation 90%. He has bilateral expiratory wheezes. His ECG reveals multifocal atrial tachycardia (MAT) (discrete P waves with at least three different morphologies).For the above patient with an arrhythmia, select the most appropriate treatment.