Effects of angioplasty balloon inflation time on arterial contractions and mechanics.

The purpose of this study was to characterize and compare the immediate effects of short and long angioplasty inflation times on arterial contractions and passive mechanics and thereby determine if there is a potential advantage obtained by increasing the duration of balloon inflation. In each of 10 nonatherosclerotic New Zealand rabbits, one external iliac artery was dilated for 20 seconds, and the contralateral artery was dilated for 2 minutes. Although angioplasty stretched the arteries 27% and 30% for the short and long dilations respectively, the pre- and post-angioplasty arteriographic diameters were not different. Both short and long dilations had equal effects on passive biomechanics: circumferential wall stress was increased (P less than .01); wall thickness was decreased (P less than .01); the incremental elastic modulus was increased (P less than .01). In vitro studies of arterial rings demonstrated that maximal active contractile force in response to KCl (70 mM) was significantly (P less than .05) less for dilated arteries than for undilated arteries. More importantly, maximal active force after the 2-minute dilations was significantly (P less than .05) less than after the 20-second dilations. These results suggest that, when dilating normal arteries, increasing angioplasty balloon inflation time from 20 seconds to 2 minutes offers no mechanical advantage but produces more smooth muscle cell dysfunction, which may reduce vasospasm and restenosis after angioplasty.