Terkelsen and colleagues conducted a review of historical data to determine the effect on mortality of various delays in treating ST-segment elevation myocardial infarction (STEMI) patients with percutaneous coronary intervention (PCI). The study included 6,209 patients who had STEMI or bundle branch block MI and were seen at three PCI centers in Denmark from January 2002 to December 2008. The authors examined treatment delay (symptom onset to guiding-catheter insertion), patient delay (symptom onset to contacting emergency services), system delay (contact with emergency services to guiding-catheter insertion), prehospital system delay (contact with emergency services to arrival at the PCI center), and door-to-balloon delay (PCI center arrival to guiding-catheter insertion).

System delays, as well as door-to-balloon delays, were shorter when patients were triaged directly to a PCI center instead of transferred there from a local hospital. Of all the types of delays examined, system delays had the greatest effect on mortality. Cumulative mortality increased with longer system delays: 15%, 23%, 28%, and 31% cumulative mortality for delays of up to 60, 61 to 120, 121 to 180, and 181 to 360 minutes, respectively. Prehospital system delays and door-to-balloon delays were also directly related to mortality. However, after adjusting for other covariates, treatment and patient delays were not.