Chest radiographic findings were normal. Laboratory findings revealed creatine kinase, 607 U/L (reference range, 26 to 189 U/L), creatine kinase MB fraction, 47.96 ng/mL; cardiac troponin I, 11.27 ng/mL (reference range, 0.00 to 1.5 ng/mL); and normal hemoglobin and platelet count. The WBC count was 11.2 k/cvmm. The patient was administered aspirin and IV metoprolol. Unfractionated heparin was started IV, and reteplase was administered, 10 U IV over 2 min, followed by a second dose of 10 U administered 30 min later. After the second dose of reteplase, shortness of breath suddenly developed, with tachypnea, slurred speech, and confusion. His physical examination showed a respiratory rate of 36 breaths/min, BP of 100/75 mm Hg, heart rate of 98 beats/min, and drop in oxygen saturation by finger oximetry to 88% on 4 L of oxygen.