The IHCA paradox: high early mortality, yet comparable long-term survival in STEMI patients.

In-hospital cardiac arrest in STEMI (STEMI-IHCA) patients poses a formidable mortality risk, yet comprehensive survival data remain scarce. This study compared clinical characteristics and outcomes of STEMI-IHCA versus non-cardiac arrest (non-CA) patients. A cohort of 3311 STEMI patients, treated in the Cath lab and transferred to the intensive cardiac care unit, was retrospectively analyzed over a 21-year period (2003-2024). Of these, 208 (6.3%) had experienced STEMI-IHCA. The mean age was 66.2 ± 12.6 years; 77.8% were male. STEMI-IHCA patients more frequently had peripheral artery disease, multivessel disease, and renal impairment. In contrast, non-CA patients had higher rates of dyslipidemia and smoking. A striking 72.7% of STEMI-IHCA cases presented with a shockable rhythm, achieving rapid ROSC (< 1 min).Despite this, in-hospital mortality for STEMI-IHCA was drastically higher (25.5 vs. 2.8% for non-CA, p < 0.01), with most deaths occurring within three days (66 vs. 44.2%, p < 0.01). Predictors of in-hospital mortality were IHCA, older age, peripheral artery disease, reduced LVEF, and higher TIMI risk index. Among patients discharged alive, long-term mortality over a 96-month follow-up was similar between STEMI-IHCA and non-CA patients (36.8 vs. 33.3%, p = 0.37), confirmed by Kaplan-Meier analysis (p = 0.73) as well. Our findings confirm the high risk of in-hospital mortality risk associated with STEMI-IHCA. Nevertheless, among patients discharged alive, particularly with rapid ROSC, the long-term prognosis can align remarkably with that of STEMI patients who did not experience IHCA. This underscores the critical importance of prompt intervention as a powerful determinant of favorable long-term outcomes.