1. RESULTS : METHODS:  The e-MUST registry includes all out-of- hospital STEMI, attended by a mobile intensive care unit, in the great Paris area (France). With an area of 12.012 km 2, this region represents only 2% of the country’s surface, but at the date of the 1 st January 2007, 11.598.800 inhabitants lived here, representing near to 20% of the French population.  Clinical characteristics and therapeutic strategies were collected for all patients included.  Two thirds of the cohort was randomly selected to identify independent predictors of OHCA and to build a risk score using logistic regression (derivation sample).  This score was validated in the remaining third of the cohort (validation sample) where calibration and discrimination were evaluated using Hosmer-Lemeshow goodness-of-fit test and the area under the receiving operative curve respectively. CONTEXT :  At the acute phase of STEMI, some patients are at high risk of sudden death, mainly due to ischemic arrhythmia.  The prognosis of these patients is often very bad, except when resuscitation care are provided promptly.  Identification of Out-of-hospital cardiac arrest (OHCA) high risk patients in the early phase of STEMI is a challenge and has strong implications for their prognosis.  Predictors of OHCA in this setting have been studied sparingly. CONCLUSION :  In the acute phase STEMI, younger age, heart failure, infarction in the anterior section and shorter delay between chest pain onset and first medical contact are independent predictors of OHCA.  These variables should be routinely collected during the call in order to identify patients at high risk of OHCA and to adapt rescue strategy.  In the future we plan to refine this analysis by including baseline risk variables. PURPOSE :  The aim of our study was to assess predictive factors of an OHCA in the acute phase of STEMI, and create a risk score of this event. Risk factors for out-of-hospital cardiac arrest in the acute phase STEMI. The e-MUST registry O. Giovannetti 1, S. Escolano 2, JP. Empana 2, S. Bataille 3, C. Caussin 4, H. Benamer 5, MC. Perier 2, A. Cariou 6, X. Jouven 2, Y. Lambert 7 (1)Tours Regional University Hospital, Hospital Trousseau, Department of Emergency, Tours, France (2) Inserm U970 - Paris Cardiovascular Research Center (PARCC), Cardiovascular Epidemiology-Sudden Death, Paris, France (3) Paris Region Agency of Hospitalisation, Paris, France (4) Marie Lannelongue Hospital, Cardiology Department, Paris, France (5) European Hospital of Paris La Roseraie, Cardiology Department, Paris, France (6) APHP University Hospital Cochin, Medical Intesive Care Unit, Paris, France (7) Hospital of Versailles, Emergency Medical Service, Paris, France  From January 2002 to December 2008, 11744 consecutive patients were included in the e-MUST registry.  The median age was 60 years (range 19 - 105), 77.5% were males., and OHCA occured for 751 (6.4%) (table 1). Table 1 : Clinical characteristics and therapeutic strategies in the derivation and validation samples. Parameters Derivation sample Validation sample (n=7751)(n=3993) Age, yr, median, (IQR)60 (51 - 73) Male, n (%)6023(77.9%)3082 (77.2%) Delay from pain onset to first medical contact, min, median, (IQR) 89 (49 - 200)91 (50 – 201) Location ST-segment elevation, n (%) Anterior3463 (45.1%)1728 (43.7%) Inferior3826 (49.8%)1990 (50.3%) Unknown396 (5.1%)239 (6%) Heart failure, n (%)398 (5.2%) 227 (5.7%) VF / VT, n (%)1084 (14%)556 (13.9%) Out-of-hospital cardiac arrest, n (%)518 (6.7%)233 (5.8%) Out-of-hospital death, n (%)60 (0,8%)33 (0.8%) Out-of-hospital thrombolysis, n (%)2061 (26.6%)1097 (27.5%) Hospital coronary angiography, n (%)6839 (88.9%)3512 (88.7%) Hospital's death, n (%)370 (5.4%)192 (5.4%) Table 2 : Results of the multivariate analysis in the derivation sample (n=7534) : independent predictors of OHCA at the acute phase STEMI. VariablesnOHCAOR95% CIScore Age > 60 yrs18292061 0 50-60 yrs20151521.4[1.3 – 2]3 < 50 yrs36901541.6[1.1 - 1.8]5 Infarct location Inferior3757861 0 Anterior33942791.7[1.4 - 2.1]5 Unknown383303.5[2.5- 4.9]12 Heart failure 38784 4.7[3.5 -6.2] 15 Delay from pain onset to first medical contact > 3 h1810661 0 1 h – 3 h2050981,4[1 - 1.9]3 ½ h – 1 h14681072.3[1,6 - 3,1]8 < ½ h22062383.3[1,4 - 4,4]12 Figure 1: AUC curve  Independent predictors were determined in the validation sample and used to build the risk score (table 2).  In the validation sample, discrimination was fairly good (AUC =0.70 [0.66-0.73]) (figure 1), and calibration adequate (Hosmer-Lemeshow goodness-of-fit test : p=0.22) (figure 2). AUC = 0.7 Cumulative risk of OHCA Figure 2: Predicted and observed OHCA by deciles, in the validation sample Deciles