Endometrial ablation with a vaporizing electrode. I. Evaluation of in vivo effects

Background. To evaluate histologically and histochemically the physical and thermal effects of a vaporizing electrode as compared with a standard cutting loop in the performance of endometrial ablation. Methods. Operative hysteroscopy was performed on 20 menorrhagic patients immediately before hysterectomy. Part of the posterior uterine wall was treated with a cylindrical, grooved, vaporizing electrode and undamped current set at 200 watts, and part with a standard cutting loop and undamped current set at 100 watts. A mucosal strip of about 1 cm width was left intact between the two treatment areas. Specimens underwent histologic examination after hematoxylin and eosin staining and histochemical assessment of thermal injury was based on detection of the respiratory enzyme dihydronicotinamide adenine dinucleotide diaphorase. Results. The mean (standard deviation) endometrial thickness as determined on the untreated area of the posterior uterine wall was 1.08 (0.36) mm. The mean depth of furrows was 3.10 (0.90) mm with the use of the vaporizing electrode and 3.41 (1.11) mm after passage of the cutting loop. Corresponding values when thermal necrosis beneath the ablated area was assessed by the dihydronicotinamide adenine dinucleotide diaphorase technique were, respectively, 1.80 (0.40) mm and 0.41 (0.20) mm (mean difference, 1.39 mm; 95% confidence interval, 1.19 to 1.59; p <0.001, Mann-Whitney U test). Conclusions. A vaporizing electrode and a standard cutting loop obtained a similar degree of endomyometrial ablation. However, the depth of the thermal effect of the former electrode was significantly greater. Clinical studies are warranted, also considering the potential limitation of fluid absorption and menorragia recurrence when a vaporizing electrode is used.