Prospective observational cohort study of time saved by prehospital thrombolysis for ST elevation myocardial infarction delivered by paramedics

Abstract

Objectives: To evaluate a system of prehospital thrombolysis, delivered by paramedics, in meeting the national service framework's targets for the management of acute myocardial infarction.

Design: Prospective observational cohort study comparing patients with suspected acute myocardial infarction considered for thrombolysis in the prehospital environment with patients treated in hospital.

Setting: The catchment area of a large teaching hospital, including urban and rural areas.

Participants: 201 patients presenting concurrently over a 12 month period who had changes to the electrocardiogram that were diagnostic of acute myocardial infarction or who received thrombolysis for suspected acute myocardial infarction.

Main outcome measures: Time from first medical contact to initiation of thrombolysis (call to needle time), number of patients given thrombolysis appropriately, and all cause mortality in hospital.

Results: The median call to needle time for patients treated before arriving in hospital (n=28) was 52 (95% confidence interval 41 to 62) minutes. Patients from similar rural areas who were treated in hospital (n=43) had a median time of 125 (104 to 140) minutes. This represents a median time saved of 73 minutes (P < 0.001). Sixty minutes after medical contact 64% of patients (18/28) treated before arrival in hospital had received thrombolysis; this compares with 4% of patients (2/43) in a cohort from similar areas. Median call to needle time for patients from urban areas (n=107) was 80 (78 to 93) minutes. Myocardial infarction was confirmed in 89% of patients (25/28) who had received prehospital thrombolysis; this compares with 92% (138/150) in the two groups of patients receiving thrombolysis in hospital.

Conclusions: Thrombolysis delivered by paramedics with support from the base hospital can meet the national targets for early thrombolysis. The system has been shown to work well and can be introduced without delay.

Fig 1

Approximate catchment area for “chest pain” referrals to Ninewells Hospital in Dundee, Scotland. The “urban” group refers to patients from postcodes DD1 to DD6. The “study area” is outlined in red and refers to postcodes DD10 and DD11

Fig 2

Patients with diagnosis of ST elevation myocardial infarction included in the study (n=282). Group 1 refers to patients within the “urban” area. Group 2 refers to patients from rural areas who were considered for thrombolysis in hospital. Group 3 refers to patients from the study area who were considered for prehospital thrombolysis

Fig 3

Composition of time delays—“call to needle” time. For values, see table

Fig 4

Cumulative distribution of call to needle time. Group 1 refers to patients from urban area receiving thrombolysis in hospital. Group 2 are patients from rural areas who received thrombolysis in hospital. Group 3 are patients from the study area who received prehospital thrombolysis