Photoangioplasty Recount: Clear Punch Or Dimpled Chad? Response

Editor must not exceed 400 words in length and must be limited to three authors and five references. They should not have tables or figures and should relate solely to an article published in Circulation within the preceding 12 weeks. Authors of letters selected for publication will receive prepublication proofs, and authors of the article cited in the letter will be invited to reply. Replies must be signed by all authors listed in the original publication. Please submit three typewritten, double-spaced copies of the letter to Herbert L. Fred, MD, ࡆ the Circulation Editorial Office. Letters will not be returned. The recent article by Rockson, et al 1 presents the results of a phase I trial of photodynamic therapy in patients with peripheral arterial disease. This report seems to be based on preliminary data that do not provide convincing evidence to support its conclusion, ie, that photoangioplasty holds promise as an alternative intervention for flow-limiting atherosclerosis. The lack of a control group and limiting the intervention to a single lesion that is not necessarily a flow-limiting stenosis are especially problematic. Smooth muscle cells constitute no more than 2% to 5% of the volume of the atherosclerotic plaque. Consequently, there is no basis for assuming that the cytotoxic effect of photodynamic therapy would reduce the plaque volume sufficiently to be hemodynamically significant. Even if these cells are killed and lysed, an explanation as to what happened afterward to the major extracellular components of the plaque (cholesterol deposits and fibrous and calcified material) seems necessary and important. Because there are large differences in the diameter of iliac, common femoral, and superficial femoral arteries, the distance between the laser source and vessel wall and, consequently, the laser dosages were different and might also have affected the results. The authors also need to address the issue of thermal injury, because the relatively high laser intensity that was used may cause thermal damage to the arterial wall and increase platelet aggregation with possible late thrombosis. Finally, modest clinical improvement in this study may also be due to the laser irradiation of blood. Several groups 2,3 previously demonstrated a beneficial effect of low-intensity laser irradiation on local circulation. It was previously demonstrated that endoluminal low-intensity laser irradiation decreases the volume of atherosclerotic plaques in humans. 4 Histological examination and ultrastructural analysis of the material obtained from surgical specimens of previously illuminated segments revealed that this type …