Thermal compression and molding of atherosclerotic vascular tissue with use of radiofrequency energy: Implications for radiofrequency balloon angioplasty

Abstract

The combined delivery of pressure and thermal energy may effectively remodel intraluminal atherosclerotic plaque and fuse intimal tears. To test these hypotheses with use of a non-laser thermal energy source, radiofrequency energy was delivered to postmortem human atherosclerotic vessels from a metal “hot-tip” catheter, block-mounted bipolar electrodes and from a prototype radiofrequency balloon catheter. Sixty-two radiofrequency doses delivered from a metal electrode tip produced dose-dependent ablation of atherosclerotic plaque, ranging from clean and shallow craters with histologic evidence of thermal compression at doses <40 J to tissue charring and vaporization at higher (>80 J) doses. Lesion dimensions ranged between 3.14 and 3.79 mm in diameter and 0.20 and 0.47 mm in depth. Tissue perforation was not observed.To test the potential for radiofrequency fusion of intimal tears, 5 atm of pressure and 200 J radiofrequency energy were delivered from block-mounted bipolar electrodes to 48 segments of human atherosclerotic aorta, which had been manually separated into intima-media and media-adventitial layers. Significantly stronger tissue fusion resulted (28.5 ± 3.3 g) with radiofrequency compared with that with pressure alone (4.8 ± 0.26 g; p < 0.0001). A prototype radiofrequency balloon catheter was used to deliver 3 atm of balloon pressure with or without 200 J radiofrequency energy to 20 postmortem human atherosclerotic arterial segments. In 10 of 10 radiofrequencytreated vessels, thermal “molding” of both normal and atherosclerotic vessel wall segments resulted with increased luminal diameter and histologic evidence of medial myocyte damage. In 10 of 10 control vessels treated with balloon pressure alone, vascular geometry and luminal diameter recoiled to predilation values.Thus, delivery of radiofrequency energy in combination with pressure to atherosclerotic tissue effectively molds atherosclerotic plaque and vessels and produces medial myocyte damage and strong tissue fusion. These observations may have important implications for preventing acute and chronic restenosis after balloon angioplasty.