Background
Early percutaneous coronary intervention (PCI) is recommended for ST-segment elevation myocardial infarction (STEMI) treatment. Delays in time-to-PCI, kept within guideline recommendations, have seldom been investigated.

Objectives
The purpose of this study was to investigate the consequences of delay, due to system factors or hospital distance, for the time between last patient distress call and PCI.

Methods
Registry-based cohort study including times of first call to medical services, admission and PCI for patients admitted with STEMI in Copenhagen, Denmark (2014-2018). The main combined outcome included death, recurrent myocardial infarction, or heart failure estimated at 30 days and 1 year from event. Outcomes according to time from call to PCI (system delay) and door-to-balloon time were standardized to the STEMI population using multivariate logistic regression.

Results
In total, 1,822 STEMI patients (73.5% male, median age 63.3 years [Q1-Q3: 54.6-72.9 years]) called the emergency services ≤72 hours before PCI (1,735, ≤12 hours). The combined endpoint of 1-year cumulative incidence was 13.9% (166/1,196) for patients treated within 120 minutes of the call and 21.2% (89/420) for patients treated later. Standardized 30-day outcomes were 7.33% (95% CI: 5.41%-9.63%) for patients treated <60 minutes, and 11.1% (95% CI: 8.39%-14.2%) for patients treated >120 minutes.

Conclusions
The risk of recurrent myocardial infarction, death, and heart failure following PCI treatment of STEMI increases rapidly when delay exceeds 1 hour. This indicates a particular advantage of minimizing time from first contact to PCI.