[Percutaneous coronary excimer laser angioplasty]

Available preliminary clinical studies have shown that ablation of atherosclerotic plaques can be achieved by means of pulsed excimer laser coronary angioplasty via flexible energy transmission systems. The goal of current studies using improved catheter technology is to enhance the acute success rate since, based on initial studies, it can be assumed that only about 40 to 45% of the patients can be successfully treated. The on-going investigations were carried out primarily with three different excimer laser systems which employ a wavelength of 308 nm but differing pulse widths and transmission systems. In the first American multicenter study by Litvack and Margolis a catheter system was used with a pulse width of 180 to 220 ns. The fibers have a shaft diameter of 100 microns with a conically-thickened distal end measuring 200 microns, the ablative area encompasses 35 to 45% of the total catheter tip surface. The excimer laser used in the second American multicenter study by Sanborn and Isner has a pulse width of 120 ns. This catheter is relatively unflexible due to the 200 microns fiber diameter. The ablative catheter tip area is 25 to 30%. In Tübingen a system was used with a pulse width of 60 ns. The energy is transmitted through fibers with a diameter of 100 microns. The effective ablative area in the first series of patients was about 15%, in the second series about 25 to 30%. At present, the energy density of all three systems is comparable with at least 25 to 35 mJ/mm2. Since there is currently no means for accurate assessment, the question of whether a shorter pulse width of comparable energy density is more effective than the longer pulse width, remains an open issue. The flexibility of the systems used by Margolis and in Tübingen enable ablation not only of proximal, but also arteriosclerotic plaques located in the middle-third of vessels. The flexibility and steerability, however, are inferior to balloon catheter systems. In the study carried out by Litvack and Margolis, in which more than 600 patients have been treated, and the results from 514 patients reported, there was no patient selection in the first series. The study by Sanborn and Isner included 88 patients. Due to the relatively unflexible catheter system, only those patients were treated who had proximal stenosis of the left anterior descending or right coronary artery or marginal branches of the circumflex artery without marked tortuosity.(ABSTRACT TRUNCATED AT 400 WORDS)