Time from symptom onset to treatment and outcome in prehospital thrombolysis for acute ST-elevation myocardial infarction

Abstract

Background: Prehospital thrombolysis for acute ST-elevation myocardial infarction shortened treatment by 60 minutes, and created a large patient group who were treated within two hours.

Objectives: We analysed our database of patients undergoing prehospital treatment for acute ST-elevation myocardial infarction in search of characteristics for a better outcome in the early treatment group.

Methods: From 1994 to 2000 a total of 475 patients were treated using prehospital administration of anistreplase (in 407 patients) or reteplase (in 68 patients) after diagnosis was confirmed with transtelephonic transmission of the ECG. There was no age limit. The patient data were divided into two groups: one treated within two hours after onset of pain (291 patients, 62%), and one treated later (171 patients, 37%). Thirty-day mortality, symptoms and clinical signs of heart failure were used as parameters of outcome. Both univariate and stepwise logistic regression analyses were used to test 30-day mortality against age, actual time to treatment, prior myocardial infarction, hypertension, diabetes, anterior myocardial infarction, Killip class, systolic blood pressure and heart rate at presentation.

Results: Overall 30-day mortality was 9.1%. Overall heart failure was in 16.6% of patients. Both mortality (5.5% vs. 15.5%, p<0.02) and heart failure (12.7% vs. 23.2%, p<0.02) were significantly lower in the early treatment group compared with the group treated late. Independent parameters showing a relation with 30-day mortality were age, time to treatment, hypertension and prior myocardial infarction. Age, time to treatment, hypertension and hyperlipidaemia were identified as predicting heart failure within the first 30 days.

Conclusion: With prehospital thrombolysis, both 30-day mortality and heart failure were lower in an early treatment group with acute ST-elevation myocardial infarction. Independent variables for 30-day mortality were age, hypertension, prior myocardial infarction and time to treatment, and age, hypertension, hyperlipidaemia and time to treatment were independent predictors for heart failure.

Keywords: ST-elevation; myocardial infarction; prehospital thrombolysis.