We report a case of acute pulmonary embolism with hemodynamic instability diagnosed by a computed tomography pulmonary angiogram. The patient developed pulseless electrical activity during systemic thrombolytic therapy with recombinant tissue plasminogen activator. Successful return of spontaneous circulation was achieved after immediate cardiopulmonary resuscitation with chest compressions for 6 min. His electrocardiogram (ECG) on arrival in the emergency department displayed sinus tachycardia, an S wave in lead I, a Q wave in lead III, incomplete right bundle branch block (RBBB), T-wave inversion (TWI) in leads V1-V3, ST elevation in leads aVR and V1, and ST depression in leads I, II, III, aVF, and V4-V6. These characteristic ECG changes might have prognostic value for clinical deterioration. He recovered after treatment. After discharge, the ECG showed resolution of TWI in leads V1-V3 and incomplete RBBB, suggesting recovery from right ventricular dysfunction, which was confirmed by an echocardiogram on follow in the outpatient department.