Acute effect of a variable pulse width Nd:YAG laser combined with hematoporphyrin monomethyl ether-mediated photodynamic therapy on a cockscomb model of nevus flammeus.

BACKGROUND Nevus flammeus (NF) is a congenital vascular malformation. OBJECTIVES To investigate the acute effect of a variable pulse width Nd:YAG laser combined with hematoporphyrin monomethyl ether (HMME)-mediated photodynamic therapy (PDT) on a cockscomb model of NF. MATERIAL AND METHODS Forty-two leghorn roosters were randomly divided into the following 7 groups: group A1 (treated with HMME-mediated PDT; energy density of 75 J/cm2), group A2 (treated with HMME-mediated PDT; 125 J/cm2), group A3 (treated with HMME-mediated PDT; 150 J/cm2), group A4 (treated with HMME-mediated PDT; 175 J/cm2), group B (treated with a variable pulse width Nd:YAG laser), group C (treated with a variable pulse width Nd:YAG laser and HMME-mediated PDT), and group D (the control group). Changes in the cockscomb tissues were observed visually and microscopically on days 1, 3, 7, and 14 after treatment. The capillary reduction and the ratio of collagen type I to type III were examined. RESULTS The response rate was higher in groups A3 and A4 than in group B. In group A, a higher energy density resulted in a higher response rate and a greater capillary reduction (p < 0.05 for all). However, we concluded that PDT at an energy density of 175 J/cm2 is not suitable for treating NF, as severe tissue damage, markedly lower capillary numbers, and markedly higher collagen type I:III ratios were observed in the cockscombs treated at this energy density; instead, 150 J/cm2 may be a more appropriate energy density. Moreover, HMME-mediated PDT at 150 J/cm2 combined with a variable pulse width Nd:YAG laser achieved better treatment outcomes than PDT or a variable pulse width Nd:YAG laser alone (p < 0.05 for both). CONCLUSIONS Compared to PDT or a variable pulse width Nd:YAG laser alone, the combination of the 2 therapies achieved a better acute effect in treating a cockscomb model of NF, and 150 J/cm2 may be a suitable energy density for PDT.