The aim of the study is to investigate whether occluding the abdominal aorta with an external device could be a potential therapeutic option in cases of non-traumatic cardiac arrest occurring outside of a hospital.

In cardiac arrest, the heart suddenly stops beating, causing the circulation of blood to collapse. In this situation, vital organs-especially the brain and the heart itself-are no longer adequately supplied with oxygen. Without immediate treatment, severe damage or death occurs within minutes.

The study therefore examines a specific intervention: the temporary occlusion of the abdominal aorta, which carries blood to the lower regions of the body. If this artery is blocked for a short period, the available blood can be redirected more effectively to the upper parts of the body. In theory, this could improve the oxygen supply to these organs and increase the likelihood that the heart will resume beating or that neurological damage can be reduced.

Background There is now a substantial body of experimental and clinical research on resuscitative endovascular balloon occlusion of the aorta (REBOA), highlighting its potential role in resuscitation medicine. As early as 1993, a porcine model was used for the first time to investigate the effect of REBOA on the quality of cardiopulmonary resuscitation. In this study on anesthetized pigs, temporary occlusion of the aorta during cardiopulmonary Resuscitation (CPR) resulted in a significant improvement in central hemodynamic parameters, particularly an increase in coronary perfusion pressure.

Initial case series from the past 10 years have also examined the use of REBOA in non-traumatic cardiac arrest. Despite overall small sample sizes, they demonstrated significant increases in end-tidal CO₂ (etCO₂) as well as higher rates of any ROSC. A common feature of both studies was the relatively long interval from emergency call to REBOA application, exceeding 45 minutes in each.

More recent studies from the past five years have confirmed these conclusions: REBOA placement led to improvements in various resuscitation indices. However, the procedure is often technically challenging, and when performed in-hospital, it typically took place more than 45 minutes after the initial emergency call. Two of the centers involved in these studies have now started to recruit for randomized controlled trials with more than 200 patients.

As an alternative to REBOA placement in Zone 3 for hemodynamically unstable patients in hemorrhagic shock due to pelvic or lower extremity injuries, the Abdominal Aortic Junctional Tourniquet (AAJT) is available. The first publication appeared in 2009, and market approval in the United States was granted in 2013. The device applies external pressure on the abdomen via balloon inflation under a abdominal binder with the goal of occluding flow in the abdominal aorta.

For non-traumatic cardiac arrest, there is currently only one animal study involving six pigs. In this study, AAJT application improved blood flow and diastolic pressure in the carotid artery, but did not confer a survival benefit.

During resuscitation, a diastolic blood pressure of over 30 mmHg should be achieved. This was reaffirmed in the latest European Resuscitation Council (ERC) guidelines of 2025, as it is associated with an increased rate of survival to hospital discharge.

Case series describing the application of the AAJT in traumatic cardiac arrest have demonstrated a notably high rate of favorable physiological responses. Reported positive outcomes include a change from non-perfusing or disorganized rhythms to more organized cardiac rhythms, an increase in end-tidal carbon dioxide (etCO₂) as a surrogate marker of improved circulation and perfusion, and, in several cases, the achievement of return of spontaneous circulation (ROSC). These findings suggest that temporary aortic occlusion using the AAJT may improve central blood flow and augment coronary as well as cerebral perfusion during resuscitation efforts.

Rationale The aortic occlusion during medical cardiac arrest with REBOA has shown promising results, but time-to-occlusion often requires a significant amount of time, with a high failure rate. The aortic occlusion with the AAJT device is a faster and non-invasive approach to the same problem. This study aims to show the feasibility of this rationale in a limited amount of patients.

Inclusion Criteria:

• Cardiac arrest with indication for initiation of resuscitation
• Age ≥ 18 years

Exclusion Criteria:

• Pregnancy (suspected or confirmed)
• Age < 18 years
• Abdominal circumference does not allow application of the AAJT
• Traumatic etiology
• Planned eCPR or other intervention in which study inclusion would delay the standard of care
• Known abdominal aortic aneurysm

Due to the low number of included patients there are concerns regarding privacy.