Background: The impact of patient delay on left ventricular ejection fraction (LVEF), when system delay has performance that meets the current recommended guidelines, is poorly investigated. Methods: We evaluated a cohort of STEMI patients treated with primary percutaneous coronary intervention (pPCI) and with an ECG STEMI diagnosis to wire crossing time (ETW) 64120 min. Independent predictors of pre-discharge decreased LVEF ( 6445%) were analyzed. Results: 490 STEMI patients with both ETW time 64120 min and available pre-discharge LVEF were evaluated. Mean age was 64.2 \ub1 12 years, 76.2% were male, 19.5% were diabetics, 42.7% had and anterior myocardial infarction (MI), and 9.8% were in Killip class III\u2013IV. Median time of patient's response to initial symptoms (patient delay) was 58,5 (IQR 30;157) minutes and median ETW time was 78 (IQR 62\u201395) minutes. 115 patients (23.4%) had pre-discharge LVEF 6445%. At multivariable analysis independent predictors of decreased LVEF ( 6445%) were anterior MI (OR 4,659, 95% CI 2,618-8,289, p < 0,001), Killip class (OR 1,449, 95% CI 1,090-1,928, p = 0,011) and patients delay above the median (OR 2,030, 95% CI 1,151\u20133.578, p = 0,014). These independent predictors were confirmed in patients with ETW time 6490 min. Conclusions: When system delay meets the recommended criteria for pPCI, patient delay becomes an independent predictor of pre-discharge LVEF. These findings provide further insights into the potential optimization of STEMI management and identify a target that needs to be improved, considering that still a significant proportion of patients continue to delay seeking medical care
