772-4 Intravascular Heating Facilitates Local Heparin Delivery and Attenuates Washout During Balloon Angioplasty with Hydrogel-Coated Balloons

Abstract

Although previous studies have demonstrated that heparin can be delivered to the arterial wall during balloon angioplasty with hydrogel-coated balloons, drug washout over the first hour is rapid. The purpose of this study was to determine whether vascular heating during local heparin delivery with hydrogel-coated, radiofrequency-powered thermal angioplasty balloons would affect immediate drug deposition and the subsequent persistence of heparin within the arterial wall. To evaluate the effect ofheat on heparin deposition, fluorescein-labeled heparin was delivered in vitro to 13 bovine coronary arteries either at 50°C (n = 3), at 60°C (n = 3) or without heat (n = 7). Heparin deposition was graded on a 1–3 scale as extending into the inner 1/3, the middle 1/3 or outer 1/3 of the arterial wall. To assess the effect of heat on the intramural persistence of heparin , 3 H-heparin was delivered in vivo to 13 porcine peripheral artery pairs. The balloon:artery ratio was 1.2: 1 as guided by intravascular ultrasound. One artery in each pair was heated during heparin delivery to either 50°C (n = 11) or 80°C (n = 2). The contralateral control vessel was not heated. Arteries were harvested at one hour for scintillation counting. In both the in vivo and in vitro studies, balloon inflations were at 6 atm for 2.5 minutes. In all heated vessels thermal energy was applied for 90 secs. Supplemental heating during local drug delivery significantly increased both the immediate deposition and the persistence of intramurally delivered heparin. In vitro, the heparin deposition score was 2.3 ± 0.5 for heated arteries and 1.3 ± 0.8 for controls (p = < 0.03). In vivo, more heparin was present at one hour in the heated arteries than in the control arteries in 11 of 13 vessel pairs (heated vessels, 58 ± 46 units; non-heated controls, 43 ± 42 units, p = 0.02). Vascular heating at the time of local heparin delivery with hydrogei-coated balloons increases both the immediate delivery and the persistence of heparin in the arterial wall.