Temperature affects thrombolytic efficacy using rt-PA and eptifibatide, an in vitro study

Abstract

The potential for hypothermia as a neuroprotectant during stroke has led to its increase in clinical use. At the same time, combination pharmaceutical therapies for ischemic stroke using recombinant tissue plasminogen activator (rt-PA), and GP IIb-IIIa inhibitors, such as Eptifibatide (Epf ), are under study. However, there is little data on how the reactions triggered by these agents are impacted by temperature. Here, clot lysis during exposure to the combination of rt-PA and Epf is measured in an in vitro human clot model at hypothermic temperatures. The hypothesis is that lytic efficacy of rt-PA and Epf decreases with decreasing temperature. Whole blood clots from 31 volunteers were exposed to rt-PA (0.5 μg/mL) and Epf (0.63 μg/mL) in human fresh-frozen plasma (rt-PA+Epf ), rt-PA alone in plasma (rt-PA Alone), or to plasma alone (Control), at temperatures from 30°C to 37°C, for 30 minutes. Clot lysis was measured using a microscopic imaging technique; the mean fractional clot loss (FCL) at 30 minutes was used to determine lytic efficacy. Temperature had a significant impact on FCL in clots exposed to rt-PA+Epf, with the FCL being lower at 30°C to 36°C than at 37°C. The FCL remained significantly higher for rt-PA+Epf–treated clots than Controls regardless of temperature, with the exception of measurements made at 30°C when no significant differences in the FCL were observed between groups. The use of hypothermia as a neuroprotectant may negatively impact the therapeutic benefit of thrombolytic agents.

FIG. 1.

Fractional clot loss (FCL) as a function of temperature with human fresh-frozen plasma (hFFP) alone (Control), 0.5 μg/mL recombinant tissue plasminogen activator (rt-PA) in hFFP (rt-PA Alone), and 0.5 μg/mL rt-PA and 0.63 μg/mL Eptifibatide (rt-PA+Epf ) in hFFP. Error bars denote 95% confidence intervals. *FCL (rt-PA+Epf ) ≥FCL (Control), p≤0.05. **FCL (rt-PA+Epf ) equivalent for T=32°C–36°C, p>0.1.