The functional and morphological consequences of balloon catheter injury in veins

Endovascular procedures are now used to treat occlusive arterial and venous diseases. However, after arterial catheter injury, intimal hyperplasia develops and there is altered endothelial and smooth muscle cell vasoreactivity of the vessel segment. This study examines the morphology and vasoreactivity of veins which have undergone balloon catheter injury. Under direct vision, 22 jugular veins of 11 New Zealand White rabbits were catheterized with a Fogarty balloon catheter (4Fr, three passes, 0.75 ml H₂O inflation). Ten uninstrumented jugular veins from 5 additional animals were used as controls. Immediately after balloon injury, 10 jugular veins were harvested. Scanning electron microscopy of these vessels confirmed complete endothelial denudation and no in vitro endothelium dependent relaxation was observed. After 28 days, 12 veins were harvested. There were no occlusions. Histologically, the 28-day balloon-injured veins had an almost confluent endothelium. However, there was medial hypertrophy but no development of intimal hyperplasia. There were no significant changes in the contractile responses of the balloon-injured veins after 28 days to norepinephrine. Bradykinin and histamine responses were markedly attenuated. Following bradykinin precontraction, balloon-injured veins showed diminished acetylcholine sensitivity with a reduced maximal response, and a small decrease in serotonin sensitivity with a markedly decreased maximal response. In contrast, there was an increased sensitivity in response to sodium nitroprusside without a change in maximal response in precontracted balloon- injured veins. This study shows that after 28 days venous balloon injury does not induce the development of intimal hyperplasia but does reduce overall endothelial dependent relaxation (acetylcholine- and serotonin-mediated) with increased sensitivity to endothelial independent relaxation (sodium nitroprusside-mediated). These findings would suggest that when compared to arterial balloon injury, venous balloon injury does not carry the same histological and vasoconstrictive sequelae but does demonstrate similarly impaired endothelial cell function.