REBOA in Nontraumatic OHCA

Inclusion Criteria: * Adult nontraumatic OHCA * Witnessed arrest * Arrival at ER from 9AM to 5PM (in South Korea) and 8AM to 8PM (in Taiwan) Exclusion Criteria: 1. age below 20 years old or over 80 years old, 2. traumatic cardiac arrest, 3. those with unwitnessed cardiac arrest, 4. pregnant patients, 5. patients who have already achieved ROSC upon arrival at the emergency department 6. pre-cardiac arrest cerebral performance category of 3-4 7. those showing evidence of cardiac arrest due to bleeding (such as gastrointestinal bleeding) 8. those suspected of having aortic disease, such as dissection, intramural hematoma, or aneurysm, by bedside ultrasound performed immediately after ED arrival or have a previous history of aortic disease 9. whose legal representative has requested termination of resuscitation efforts before study enrollment 10. declared dead at scene before randomization 11. Patients who meet the criteria for extracorporeal cardiopulmonary resuscitation (ECPR), and therefore the decision is made to perform ECPR, will not be enrolled. The ECPR criteria applies when all of the following criteria are met: pre-cardiac arrest CPC of 1-2, witnessed cardiac arrest with bystander CPR, ages between 20-70, initial shockable rhythm, ECMO pump-on available within 60 minutes of onset of cardiac arrest, and patients without end-stage diseases such as cancer, liver cirrhosis, or end-stage renal failure.