Prehospital Thrombosis Treatment in STEMI

Mortality Benefit and Treatment Timing

The European Society of Cardiology recommends prehospital initiation of fibrinolytic treatment when this reperfusion strategy is indicated, with a Class IIa, Level A recommendation 4
Treating approximately 100 patients with prehospital fibrinolytic therapy prevents one death, with approximately 30 early deaths prevented per 1000 patients treated overall when fibrinolysis is given within 12 hours of symptom onset 1
The number needed to treat (NNT) to prevent one death is 33 when fibrinolysis is given within 12 hours, with 30 deaths prevented per 1000 patients 1
Early presentation NNT is 50 when treated within 2 hours, with 20 deaths prevented per 1000 patients 1
Late presentation NNT is 50 when treated between 7-12 hours, with 20 deaths prevented per 1000 patients 1
Prehospital fibrinolysis reduces early mortality by 17% compared to in-hospital administration 1
Meta-analysis of 22 trials showed substantially larger mortality reduction with earlier treatment, with the greatest benefit in patients treated within the first 2 hours 1

The American Heart Association recommends adding enoxaparin to fibrinolytic therapy, with a primary endpoint of death or nonfatal MI of 9.9% with enoxaparin vs 12.0% with UFH 2, 3
The absolute risk reduction is 2.1% 2, 3
The NNT to prevent one death or MI at 30 days is 48 2, 3
The net clinical benefit NNT is 20 (death, MI complication, or major bleeding), with 10% with enoxaparin vs 15% with UFH 2

Major bleeding increases with enoxaparin, with 2.1% vs 1.4% with UFH 2, 3
The number needed to harm (NNH) for major bleeding is 143 2, 3
In elderly patients (≥75 years), prehospital enoxaparin at standard doses significantly increases intracranial hemorrhage in ASSENT-3 PLUS 4, 5
Age-adjusted dosing is mandatory, with no IV bolus and 0.75 mg/kg SC (max 75 mg) for first two doses in patients ≥75 years 4, 2

The European Society of Cardiology recommends confirming STEMI and timing, with symptom onset <12 hours 4
If <2 hours with large infarct and low bleeding risk, consider fibrinolysis if PCI delay >90 minutes 4
If 2-12 hours, consider fibrinolysis if PCI delay >120 minutes 4
Aspirin 150-325 mg chewed (or 250-500 mg IV) should be administered 4, 6
Clopidogrel 75 mg daily (no loading dose in elderly) should be administered 4, 6