IN-VITRO STUDY OF A RADIOFREQUENCY GUIDEWIRE AIMED AT RECANALIZATION OF TOTALLY OCCLUDED PERIPHERAL ARTERIES

A novel radiofrequency ablative system (40 msec-train pulses with twen ty 200 msec pulses at the carrier frequency of 750 KHz and 1 Hz repeti tion rate) aimed at recanalizing totally occluded peripheral arteries was investigated by means of in vitro tissue ablation from human postm orten arterial wall samples, The samples were submitted to irradiation with a guidewire 150 cm long, maximum diameter of ceramic tip 0.033 i nch positioned perpendicular to the tissue surface in saline, contrast medium or blood using varying generator power, Ablation efficacy was determined as the depth of vaporization per pulse delivered, Electrica l current for the train duration was measured as voltage at the 1 ohm- resistor. In saline, the ablation efficacy increased from 8 to 65 mu m /pulse with generator power increasing from 11 W to 27.5 W. There was no significant difference in the ablation efficacy between saline and blood. In contrast medium, the ablation efficacy was significantly low er, For the same generator power, the electrical current varied during the ablation procedure from 1.3 +/- 0.2 A at the beginning of the pro cedure to 1.1 +/- 0.2 A after the first pulses and to 2.0 A before art ery wall perforation occurred. Neither tissue ablation nor current var iations were observed when radiofrequency energy was emitted on calcif ied tissue, The diameter of craters was 0.89 +/- 0.1 mm (range: 0.85-0 .96 mm). No major thermal injury such as carbonization or charring was observed, Thus, (1) radiofrequency energy emitted through a guidewire is reliable and effective for the ablation of arterial tissue; (2) th e depth of penetration is related to the generator power; (3) the abla tion efficacy is greater in saline and blood than in contrast medium; (4) the system is not effective in highly calcified tissue; and (5) th e procedure may be monitored by electrical current measurements. (C) 1 994 Wiley-Liss, Inc.