Impact of prehospital delay on mortality in patients with acute myocardial infarction treated with primary angioplasty and intravenous thrombolysis.

Background: In patients with acute myocardial infarction treated with thrombolysis, longer times to treatment are associated with increasingly worse clinical outcome. This relation may be different for treatment with primary angioplasty.
Methods: We analyzed the pooled data of the German acute myocardial infarction registries Maximal Individual Therapy in Acute Myocardial Infarction (MITRA) and Myocardial Infarction Registry (MIR) to determine the influence of prehospital delays on hospital mortality rates. Primary angioplasty was performed in 1063 patients and thrombolysis in 7552 patients.
Results: In patients treated with thrombolysis, in-hospital time to treatment was constantly 30 minutes median. In patients treated with primary angioplasty, in-hospital time to treatment increased from 60 minutes median up to 87 minutes median with increasing prehospital delay. Hospital mortality rates slightly decreased with increasing prehospital delays in patients treated with primary angioplasty (P for trend =.02). However, in patients treated with thrombolysis, mortality rate was nonsignificantly increased (P for trend =.11). Logistic regression analysis showed no significant difference in mortality rates between primary angioplasty and thrombolysis for prehospital delays of <3 hours. However, when prehospital delay was >3 hours, thrombolysis was independently associated with a higher mortality rate compared with primary angioplasty.
Conclusions: Compared with thrombolysis, primary angioplasty is independently associated with a lower mortality rate in prehospital delays of >3 hours. The reason for this may be a time-dependent loss of efficacy to achieve reperfusion for thrombolysis but not for primary angioplasty.