Summary
This is a prospective, observational study performed in all consecutive ST-elevation
myocardial infarction (STEMI) patients who had activated clotting time (ACT) measurement
on arrival in the cathlab before coronary angiography. We studied the therapeutic
effects of a pre-hospital fixed heparin bolus dose in consecutive patients with STEMI.
A total of 1,533 patients received pre-hospital administration of aspirin, high dose
clopidogrel (600 mg) and a fixed bolus dose of 5,000 IU unfractionated heparin (UFH),
according to the national ambulance protocols. Some patients were also treated with
glycoprotein IIb/IIIa inhibitors (GPI) in the ambulance. A therapeutic ACT range was
defined according to the ESC guidelines as 200–250 seconds when patients had GPI pretreatment
and 250–350 seconds when no GPI pretreatment. Of the 1,533 patients, 216 patients
(14.1%) had an ACT within the therapeutic range, 82.3% of the patients had a too low
ACT, whereas 3.5% of the patients had a too high ACT. After multivariable analysis,
the only independent predictor of a too low ACT was increasing weight (odds ratio
1.02/kg, 95% confidence interval 1.01–1.03, p=0.001). Patients with a too low ACT
had less often an open infarct related vessel (initial TIMI flow 2,3) as compared
to patients with an ACT in range (36.5% vs. 45.9%, p=0.013). In only a minority of
patients with STEMI, pre-hospital treatment with a fixed bolus dose UFH is within
the therapeutic ACT range. Increased weight is an independent determinant of a too
low ACT. We strongly recommend weight adjusted administration of UFH in the ambulance.
Keywords
Activated clotting time - fixed bolus dose - unfractionated heparin - ST-elevation
myocardial infarction - primary percutaneous coronary intervention