Inhibition of thrombin attenuates stenosis after arterial injury in minipigs.

OBJECTIVES

We sought to determine whether brief, profound inhibition of thrombin or prothrombin activation by factor Xa limits neointimal formation and stenosis after arterial injury.

BACKGROUND

Thrombin has been implicated as a mediator of neointimal formation, but adjunctive administration of anticoagulant agents has not proven effective to decrease restenosis in patients undergoing coronary angioplasty.

METHODS

We infused recombinant desulfatohirudin (r-hirudin, bolus of 2 mg/kg body weight followed by 2 mg/kg per h, n = 9), heparin (100 U/kg per h, n = 6) or recombinant tick anticoagulant peptide (rTAP, 1-mg/kg bolus followed by 3 mg/kg per h, n = 5), a specific inhibitor of factor Xa, intravenously, beginning 15 min before and for up to 3 h after repetitive balloon hyperinflations sufficient to disrupt the internal elastic lamina in a carotid artery of minipigs with hypercholesterolemia induced by feeding them an atherogenic diet.

RESULTS

Partial thromboplastin time was increased six- to sevenfold over baseline levels at the end of the infusions of the anticoagulant agents. Lumen stenosis measured histologically 4 weeks after balloon-induced carotid injury was 29 +/- 16% (mean +/- SEM) in r-hirudin-treated, 52 +/- 19% in rTAP-treated and 76 +/- 18% in heparin-treated pigs (p < 0.02 for r-hirudin vs. heparin treatment).

CONCLUSIONS

The marked reduction of stenosis in r-hirudin-treated animals indicates that thrombin plays a major role in neointimal formation after balloon-induced arterial injury. A relatively brief interval of profound, direct inhibition of thrombin may be particularly effective to attenuate restenosis after balloon angioplasty.