It is unclear whether the impact of prereperfusion unloading on improving survival is sustained throughout all periods from the onset in patients with ST-segment elevation myocardial infarction. This study is a post hoc analysis of the Japanese registry for Pectaneous Ventricular Assist Device (J-PVAD) registry. In all patients registered in J-PVAD between February 2020 and December 2021, patients with ST-segment elevation myocardial infarction complicated with cardiogenic shock and treated with Impella support alone were selected. A total of 2 cohorts were provided based on whether the onset-to-unloading time was <
6 hours. The patients were divided into 2 groups according to prereperfusion or postreperfusion unloading in each cohort. The primary outcome was the 30-day survival rate. The independent factors of survival were identified with a multivariable Cox proportional hazard regression analysis after adjusting for the variables that were statistically significant in the univariable analysis. Patients with prereperfusion unloading had a significantly higher 30-day survival rate than patients with postreperfusion unloading (91% vs 67%, p <
0.01) in the cohort with an onset-to-unloading time ≥6 hours, whereas patients with prereperfusion or postreperfusion unloading had similar 30-day survival rates (88% vs 91%, p = 0.64) in the cohort with an onset-to-unloading time <
6 hours. A multivariable analysis revealed that prereperfusion use of Impella was an independent factor of survival (hazard ratio 0.249, 95% confidence interval 0.070 to 0.889, p = 0.03) in the onset-to-unloading time ≥6 hours cohort. In conclusion, prereperfusion left ventricular unloading could be a crucial treatment to improve the short-term survival rate when the onset-to-left ventricular unloading time was ≥6 hours.