An 80-year-old man with acute type A aortic dissection, who was preoperatively observed in the intensive care unit, suddenly became unresponsive. The patient was immediately intubated, but a pulse check was delayed because the cardiac monitor seemingly showed a normal sinus rhythm. Bedside echocardiography, while continuing cardiopulmonary resuscitation, revealed massive pericardial effusion. It indicated the patient's cardiac arrest was pulseless electrical activity (PEA) due to cardiac tamponade. After pericardiocentesis, a perfusion rhythm was restored with palpable distal pulse. He successfully underwent a prosthetic graft replacement of the ascending aorta and was discharged after physical rehabilitation.