The influence of system delay on 30-day and on long-term mortality in patients with anterior versus non-anterior ST-segment elevation myocardial infarction: a cohort study

AIM To evaluate the relationship between system delay and 30-day and long-term mortality in patients with anterior versus non-anterior ST-elevation myocardial infarction (STEMI). METHODS We conducted a prospective observational cohort study. Patients with STEMI who were transported to the Isala Hospital, Zwolle, and underwent primary percutaneous coronary intervention (pPCI) from 2005 until 2010 were included. These patients were divided into quartiles of system delay (time from first medical contact until reperfusion therapy): Q1-Q4. RESULTS In total, 3041 patients were included in our study. 41% (n=1253) of the patients had an anterior myocardial infarction (MI) and 59% of the patients (n=1788) had a non-anterior MI. Only in patients with an anterior MI, prolonged system delay was associated with a higher mortality (30-day Q1: 2.6%, Q2: 3.1%, Q3: 6.8%, Q4: 7.4%, p=0.001; long-term Q1: 12.8%, Q2: 13.7%, Q3: 24.1%, Q4: 22.6%, p<0.001). After multivariable adjustment, prolonged system delay was associated with a higher 30-day and long-term mortality in patients with an anterior MI (30 day Q2: HR 1.18, 95% CI (0.46 to 3.00), Q3: HR 2.45, 95% CI (1.07 to 5.63), Q4: HR 2.25, 95% CI (0.97 to 5.25)); long-term Q2: HR 1.09, 95% CI (0.71 to 1.68), Q3: HR 1.68, 95% CI (1.13 to 2.49), Q4: HR 1.55, 95% CI (1.03 to 2.33)), but not in patients with a non-anterior MI. CONCLUSIONS Prolonged system delay significantly increased short-term as well as long-term mortality in patients with an anterior MI. This effect was not demonstrated in patients with a non-anterior MI. Therefore, it is of the greatest importance to minimise system delay in patients who present with an anterior MI.