Smooth Excimer Laser Coronary Angioplasty (SELCA) and conventional excimer laser angioplasty: Comparison of vascular injury and smooth muscle cell proliferation

Although the excimer laser, which utilizes 'non-thermal ablation effects', has achieved encouraging results in early clinical trials, the long-term results have failed to show any advantage over conventional percutaneous transluminal coronary angioplasty (PTCA). A new system, Smooth Excimer Laser Coronary Angioplasty (SELCA), has been developed to reduce the tissue damage in the vessel wall caused by shock waves and vapour bubbles. SELCA (wavelength 308 nm, pulse duration 115 ns, repetition rate 150 Hz and energy density 50 mJ mm(-2)) lowers the amount of shock wave formation and pressure peak amplitude in the surrounding tissue by about eight times when compared to the conventional 308 nm excimer laser (ELCA). In this preclinical evaluation, this new system was compared to ELCA. Fifty New Zealand White rabbits were stimulated by repeated weak DC impulses for a period of 28 days in order to form an atherosclerotic plaque in the right carotid artery. The vessels were excised 3, 7, 14 and 28 days after laser irradiation for immunohistochemical analysis. SELCA and ELCA laser treatment lead to a decrease in maximal intimal wall thickness 3 days after intervention (control: 177 +/- 4 mu m; SELCA: 131 +/- 22 mu m; ELCA: 120 +/- 33 mu m). In the period between 3 and 28 days, a moderate increase in intimal wall thickness was observed after SELCA treatment compared to a significant increase after ELCA (28 days after intervention: SELCA: 157 +/- 22 mu m; ELCA: 274 +/- 28 mu m). Bromodeoxyuridine (BrdU) was applied 18 and 12h before excision of the vessels in order to determine the percent of cells undergoing DNA synthesis. The percent of BrdU labelled SMC in the intima (control: 13 +/- 2 cells mm(-2)) increased in both groups after 3 days (SELCA: 248 +/- 107 cells mm(-2); ELCA: 162 +/- 41 cells mm(-2)) and 7 days (SELCA: 162 +/- 55 cells mm(-2); ELCA: 279 +/- 119 cells mm(-2)). The present results demonstrate that vascular wall injury and increase in intimal wall thickness following SELCA are reduced in comparison to the results achieved with the conventional technique. Further trials are necessary to assess whether these improvements will lead to more favourable long-term results after excimer laser angioplasty.