Assessment of prognostic performances of CCU in CRA Recovery (CRAR) has already been explored but 1) Only in intra-hospital medicine, 2) in very variable timings. ACE Research focuses on the extra-hospital window and predictive value of Early CCU (within 12 minutes of rescucitation initiation) with ambitious endpoints : curable etiologies identification, early anticipation of ECMO procedures, early anticipation of organ donation process, and evaluation of intrinsic contribution criterion to resuscitation interruption.

The primary objective of ACE study is to investigate the positive predictive value (PPV) of early ultrasound asystole on the absence of CRAR. The secondary objectives are multiple and innovative despite an observational design: impact on the morbi-mortality of the target population (frequency of curable etiologies, pre-therapeutic and therapeutic delays, morbidity...), delay of ECMO implementation of an ECMO (Extracorporeal Membrane Oxygenation), failure rate of organ donation due to overdelays, construction of a multifactorial score associated with CRAR.

Prehospital Cardio-Respiratory Arrests (CRA) represent a significant cause of mortality in France (between 30,000 and 50,000 cases per year) [1]. The prognosis is particularly pejorative, since only 5 to 6% of patients will leave the hospital alive with satisfying neurological condition [2,3]. Their management in France is part of a very singular Primary Care System, based on the medicalization of medical regulation (SAMU) and effectiveness (SMUR) and is based mainly on European recommendations (cardiac massage, ventilation and cardiac rhythm analysis) [4]). European 2015 recommendations advocate for the use of Cardiac Clinical Ultrasound (CCU) in Emergency Medicine, particularly to identify curable causes of CRA. Indeed, CCU is likely to reveal various curable etiologies as tamponade, massive pulmonary embolism, deep hypovolemia or suffocating pneumothorax[5]. Their identification allows the clinician to better adjust his therapeutic strategy and consequently improve patient prognosis.

But its predictive value on the absence of Spontaneous Circulatory Activity Recovery (SCAR) focus clinicians' interest due to its impact on extracorporeal circulation procedures, organ donation or resuscitation interruption guideline. Several studies support the predictive value associated with the absence of mechanical cardiac activity and resuscitation failure [5-10]. However, proof level remains very shaky and transposition to prehospital medicine is clearly impossible (delays, management and environment differ largely). As a corollary, the European Resuscitation Council (ERC) ruled in 2015 that the prognostic performances of ultrasound asystole had not been sufficiently finely measured to consider it as a rigorous criterion for resuscitation interruption, appealing for pivotal studies [4].

ACE French National Trial fits precisely into this bibliographic gap. Our objectives are multiple: assess prognostic value of Early CCU (ECCU; ie. \

Inclusion Criteria:

• Adult (>18yo) presenting extra-hospital CRA.

Exclusion Criteria:

• Resuscitation refusal.

All adult patients receiving resuscitation by the SMUR team in an CRA are eligible