Low-flow time and neurological outcomes in AMI patients undergoing ECPR: a retrospective cohort study

Background Acute myocardial infarction (AMI) complicated by refractory cardiac arrest (CA) carries extremely high mortality and neurological disability rates. Extracorporeal cardiopulmonary resuscitation (ECPR) is a rescue intervention for this population, but outcomes after its use vary widely across individuals. Low-flow time (the interval from initiation of chest compressions to establishment of stable ECMO flow) is an important prognostic factor among ECPR-treated patients. Its association with outcomes in Chinese patients with AMI-related CA remains incompletely characterized. Methods We conducted a retrospective cohort study of 161 eligible adult patients with AMI-related refractory CA who received ECPR at our tertiary center between January 2019 and December 2025. The primary endpoint was 30-day unfavorable neurological outcome [Cerebral Performance Category (CPC) score 3-5]. Multivariable logistic regression evaluated low-flow time continuously as the primary exposure. RCS regression assessed possible nonlinearity, whereas ROC analysis provided a secondary, exploratory cohort-specific classification. We performed an exact-timing sensitivity analysis and a full-cohort interaction analysis to assess heterogeneity by arrest setting. Results Among the 161 enrolled patients, 118 (73.3%) had 30-day unfavorable neurological outcomes, including 104 deaths (64.6%). After multivariable adjustment, each additional minute of low-flow time was associated with higher odds of unfavorable outcome (aOR 1.065, 95% CI 1.036–1.096; P < 0.001). The association remained in 132 patients with exact timing (aOR 1.082, 95% CI 1.042–1.124; P < 0.001). In a parsimoniously adjusted interaction model, the estimated aOR per minute was 1.061 (95% CI 1.027–1.096) for IHCA and 1.072 (95% CI 1.023–1.124) for OHCA; the interaction was not statistically detectable ( P = 0.708). RCS did not detect nonlinearity ( P = 0.660). The exploratory 50.9-min classification was internally derived and its bootstrap cutpoints were widely distributed. Conclusions Among selected AMI patients who received ECPR, increasing low-flow time was progressively associated with unfavorable 30-day neurological outcome, with no detected nonlinear inflection or evidence of effect modification by arrest setting. These findings are prognostic among ECPR-treated patients and do not define when ECPR should or should not be initiated. The internally derived 50.9-min classification is exploratory and is not an eligibility threshold.