THE EFFECTS OF INTRAVASCULAR STENTS ON VASOMOTION IN PORCINE CORONARY-ARTERIES

Intravascular stents are being increasingly utilized in the treatment of atherosclerotic coronary artery disease, however little is known ab out the effects of stents on coronary vasomotion. The purpose of the p resent study was to compare the effects of a heparin treated tantalum stent and balloon injury on coronary artery vasorelaxation and vasocon striction. Male miniswine underwent cardiac catheterization and oversi zed balloon injury to the right and left circumflex coronary arteries. After two weeks, one artery was either balloon-injured again, or unde rwent implantation of a stent. Four weeks later, the coronary arteries were prepared for in vitro isometric ring studies. Vasodilator respon ses to bradykinin and A23187 calcium ionophore were significantly impa ired in balloon-injured vessels. The bradykinin and A23187 responses i n stented vessels showed significantly less vasorelaxation, compared t o both balloon-injured and normal vessels. There were no significant d ifferences between any of the groups in their vasodilator response to nitroprusside. Vasoconstrictor responses to acetylcholine were signifi cantly greater in balloon-injured vessels, compared to normal vessels. Stented vessels, however, showed markedly less vasoconstriction to ac etylcholine compared to both balloon-injured and normal vessels. The m aximal KCI vasoconstrictor responses in balloon injured vessels and no rmal controls were not significantly different. However, the maximal K CI responses in stented vessels showed significantly less constriction compared to both balloon injured and normal vessels. In conclusion, t he data demonstrated that coronary arteries implanted with a heparin t reated tantalum stent were capable of vasomotor activity. Both convent ional balloon angioplasty and stents resulted in impaired endothelium- dependent vasorelaxation. Endothelium-independent vasorelaxation, howe ver, was not impaired. In contrast to balloon injured vessels, stented vessels showed impaired vasoconstriction to both acetylcholine and KC I.