BACKGROUND: The benefit of prehospital 12‑lead electrocardiogram (PH-ECG) performed by emergency medical service personnel at the site of first medical contact (FMC) in patients with ST-segment elevation myocardial infarction (STEMI) with cardiogenic shock (CS-STEMI) remains unclear. This study aimed to investigate the effect of PH-ECG on door-to-device time in patients with CS-STEMI. METHODS: This study enrolled CS-STEMI (Killip class IV) patients who were transferred directly to hospitals by ambulance (n = 517) from the Kanagawa Acute Cardiovascular Registry database. Patients were divided into PH-ECG (+) (n = 270) and PH-ECG (-) (n = 247) groups. Patients who experienced out-of-hospital cardiac arrest, who did not undergo emergent coronary intervention, or whose data were missing were excluded. Patient characteristics, FMC-to-door time, door-to-device time, and in-hospital mortality were compared between the groups. RESULTS: The patient backgrounds of the PH-ECG (+) and PH-ECG (-) groups were comparable. The peak creatinine kinase level was greater in the PH-ECG (+) group than in the PH-ECG (-) group [2756 (1292-6009) IU/ml vs. 2270 (957-5258) IU/ml, p = 0.048]. The FMC-to-door time was similar between the two groups [25 (20-33) min vs. 27 (20-35) min, p = 0.530], while the door-to-device time was significantly shorter in the PH-ECG group [74 (52-103) min vs. 83 (62-111) min, p = 0.007]. In-hospital mortality did not differ between the two groups (18 % vs. 21 %, p = 0.405). Multivariable logistic regression analyses revealed that PH-ECG (+) was independently associated with a door-to-device time <
60 min [odds ratio (95 % confidence intervals): 1.88 (1.24-2.83), p = 0.003]. CONCLUSIONS: PH-ECG was significantly associated with shorter door-to-device times in patients with CS-STEMI. Further studies with larger populations and more defined protocols are required to evaluate the utility of PH-ECG in patients with CS-STEMI.