In vivo assessment of stent expansion and recoil in normal porcine coronary arteries - Differential outcome by stent design

Background-Despite the routine use of high pressure, coronary stents genera lly fail to achieve a cross-sectional area (CSA) >60% to 80% of the nominal CSA of their dilating balloon. The extent to which incomplete balloon expa nsion and postdeflation stent recoil contribute to this failure has not bee n fully evaluated. Methods and Results-Thirty-two stents (8 Gianturco-Roubin IT, 8 Palmaz-Scha tz, 8 MultiLink, and 8 NIR) were deployed in nondiseased coronary arteries of 8 Yorkshire pigs. All stents were then expanded according to 1 of 3 ball oon strategies: appropriately sized compliant balloons, oversized compliant balloons, or oversized noncompliant balloons. Continuous ultrasound imagin g was performed during stepwise balloon inflation and deflation, with an 0. 018-in imaging con positioned within the guidewire lumen of the balloon. In these normal arteries, balloon underexpansion relative to the nominal size was not observed, After balloon deflation, however, all stents showed sign ificant recoil from their maximum inflated CSA. Recoil was significantly gr eater for the coil Gianturco-Roubin II stent (30% CSA) than for the 3 slott ed-tube stent designs (15% to 17% CSA). Conclusions-In normal, compliant coronary arteries, stent recoil is the pre dominant mechanism by which stents fail to achieve the nominal CSA of their dilating balloon. The magnitude of this in vivo stent recoil is significan tly greater than reported from bench testing and varies with stent design ( coil versus slotted tube). Postdilatation strategies that result in control led stent overexpansion are needed to overcome this recoil phenomenon and r esult in a final stent CSA that approximates the reference artery CSA.