Early ambulance administration of abciximab (ReoPro, Eli Lilly) in STEMI patients did not improve either ST-segment elevation resolution (STR) or TIMI flow rate after PCI; however, it tended to improve TIMI flow pre-PCI and decreased distal embolization during procedure, according to the findings of the MISTRAL study published in the February issue of Circulation: Cardiovascular Interventions.

According to the study authors, STR is an indicator of microvascular circulation and a strong prognostic factor following reperfusion after thrombolysis or primary PCI. Similarly, a complete STR is associated with a significant decrease in myocardial infarct size and preservation of left ventricular ejection fraction (LVEF). “By rapidly and potently preventing platelet activation, the glycoprotein (GP) IIb/IIIa inhibitor abciximab has great potential for reducing microvascular damage after primary PCI,” the researchers wrote, noting that conflicting data from studies have emerged.

Thus, Patrick Ohlmann, MD, PhD, of the cardiovascular division at Nouvel Hôpital Civil in Strasbourg Cedex, France, and colleagues designed the MISTRAL (MI with ST-elevation Treated by Primary Percutaneous Intervention Facilitated by Early Reopro Administration in Alsace) study to investigate the impact of abciximab administration in the ambulance versus in the cath laboratory for patients with STEMI promptly and directly admitted to the cath laboratory.

In this prospective, randomized, double-blind study, the researchers allocated 256 patients with STEMI to receive abciximab either in the ambulance (ambulance group, 127 patients) or in the cath laboratory (hospital group,129 patients). The primary endpoint was complete (greater than 70 percent) STR after PCI.

Ohlmann et al found that complete STR was not significantly different between the two groups (before PCI, 21.6 percent vs. 15.5 percent; after PCI, 70.3 percent vs. 65.8 percent). TIMI 2 to 3 flow rates before PCI tended to be higher in the ambulance group (46.8 percent vs. 35 percent) but not after PCI (70.3 percent vs. 65.8 percent). Also, slow flow tended to be lower (5.6 percent vs. 13.4 percent), and distal embolization occurred significantly less often in the ambulance group (8.1 percent vs. 21.1 percent).

One- and six-month major adverse cardiac event (MACE) rates were low and similar in both groups, the researchers reported.

According to the study authors, the major findings of the MISTRAL study were as follows:

1. Early in-ambulance administration of abciximab did not improve post-procedural STR and post-procedural TIMI flow rates compared with routine abciximab administration in the catheterization laboratory;
2. There was a tendency toward better pre-procedural TIMI 2 to 3 flow and significantly less procedural embolization and slow flow, which taken together, suggest a possible pre-procedural therapeutic effect of early ambulance abciximab administration; and
3. Early ambulance abciximab administration did not decrease MACE at 30 days and six months and did not improve LVEF or biological infarct size.

Ohlmann and his colleagues concluded that “abciximab given very early in the course of STEMI might facilitate primary PCI by improving the visibility of the coronary anatomy, thus allowing a faster and more-accurate procedure.”  They recommended that larger studies are needed to confirm these results.