Background: Acute coronary syndrome (ACS)-related morbidity and mortality remain substantial. Data on temporal trends in in-hospital complications of ACS patients are scarce. This study sought to investigate whether the incidence of in-hospital complications of ACS patients changed over time.

Methods: Acute coronary syndrome patients prospectively enrolled in the National Registry of Acute Myocardial Infarction in Switzerland (AMIS Plus) between 2003 and 2018 and with available data on in-hospital complications were included in the analysis. Rates of in-hospital complications, including recurrent angina, recurrent myocardial infarction, cerebrovascular events, cardiogenic shock, bleeding, acute renal failure, sepsis/systemic inflammatory response syndrome (SIRS)/multiorgan dysfunction syndrome (MODS), AV block needing pacing and new-onset atrial fibrillation, were assessed for each 2-year period.

Results: Among 47,845 ACS patients, in-hospital complications significantly decreased from 22.0% in 2003/2004 to 18.9% in 2017/2018 (p for trend <0.001). An initial decline in rates of in-hospital complications to 15.7% in 2009/2010 (p for trend <0.001) was followed by a constant increase thereafter (p for trend = 0.002). While rates of recurrent angina, recurrent myocardial infarction, and cardiogenic shock decreased over time, rates of bleeding events, acute renal failure, sepsis/SIRS/MODS, and new-onset atrial fibrillation increased. Rates of in-hospital complications were higher in women, mainly due to a constantly increased risk of bleeding and AV block needing pacing.

Conclusions: The decrease in ischemic complications was paralleled by a concomitant increase in non-ischemic events. These findings emphasize that advanced strategies targeting non-ischemic complications are warranted to further improve quality of care of ACS patients.