BACKGROUND: Up to 40% of patients with ST-segment elevation myocardial infarction (STEMI) present later than 12 hours after symptom onset. However, data on clinical outcomes in STEMI patients treated with primary percutaneous coronary intervention 12 or more hours after symptom onset are non-existent. We evaluated the association between primary percutaneous coronary intervention performed later than 12 hours after symptom onset and clinical outcomes in a large all-comer contemporary STEMI cohort.

METHODS: All STEMI patients treated with primary percutaneous coronary intervention in eastern Denmark from November 2009 to November 2016 were included and stratified by timing of the percutaneous coronary intervention. The combined clinical endpoint of all-cause mortality and hospitalisation for heart failure was identified from nationwide Danish registries.

RESULTS: We included 6674 patients: 6108 (92%) were treated less than 12 hours and 566 (8%) were treated 12 or more hours after symptom onset. During a median follow-up period of 3.8 (interquartile range 2.3-5.6) years, 30-day, one-year and long-term cumulative rates of the combined endpoint were 11%, 17% and 25% in patients treated 12 or fewer hours and 21%, 29% and 37% in patients treated more than 12 hours (P<0.001 for all) after symptom onset. Late presentation was independently associated with an increased risk of an adverse clinical outcome (hazard ratio 1.42, 95% confidence interval 1.22-1.66; P<0.001).

CONCLUSIONS: Increasing duration from symptom onset to primary percutaneous coronary intervention was associated with an increased risk of an adverse clinical outcome in patients with STEMI, especially when the delay exceeded 12 hours.