Electrical thermal angioplasty: Catheter design features, in vitro tissue ablation studies and in vivo experimental findings

Abstract

A prototype electrical thermal tip catheter has been developed for ablation of atherosclerotic plaques. The operating principle is based on establishing an electric arc between a central electrode and the inside of an enclosing metallic tip to convert electrical energy to thermal energy. The metal tip catheter can be heated rapidly and boils water in a saline bath with less than 1 W of power. In vitro studies, using human atherosclerotic aortic segments, demonstrated that effective tissue ablation required more power in saline than in air (more than 9 W vs less than 1 W). The rate of tissue ablation varied with the amount of power delivered and the catheter tip pressure against tissue. In a saline field, 2-mm thickness aortic wall segments were consistently perforated in 3 seconds when 15 W of power and 20 g/mm 2 of pressure were applied. Using an atherosclerotic rabbit, in vivo electrical thermal angioplasty (3 W of power for 10-second treatment sequences) was performed in obstructed iliofemoral vessels after mechanical recanalization was attempted. Of the 7 vessels that were more than 50% narrowed (compared with contiguous normal vessel diameter), mechanical recanalization was effective in only 1, but thermal angioplasty resulting in an increased lumen diameter was successful in 6 others. The recanalized segments were 8 to 10 cm; gross morphologic and histologic examination of recanalized vessels demonstrated little or no thermal injury. In addition, significant cholesterolladen plaques remained in the vessel lumen, which appeared to have been compressed and displaced laterally. The electrical thermal tip catheter may be an alternative to laser thermal angioplasty as a therapeutic device in the treatment of human atherosclerotic disease. However, additional studies are required to determine catheter safety and reliability as well as ablation efficiency of human composition atheroma before instituting clinical trials.