Original Article
Copyright ©2012 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Nov 7, 2012; 18(41): 5870-5878
Published online Nov 7, 2012. doi: 10.3748/wjg.v18.i41.5870
Effectiveness of impedance monitoring during radiofrequency ablation for predicting popping
Hiroya Iida, Tsukasa Aihara, Shinichi Ikuta, Naoki Yamanaka
Hiroya Iida, Tsukasa Aihara, Shinichi Ikuta, Naoki Yamanaka, Department of Surgery, Meiwa Hospital, 4-31 Agenaruo-cho, Nishinomiya, Hyogo 663-8186, Japan
Author contributions: Iida H contributed to this work; Iida H and Yamanaka N designed the research; Iida H, Aihara T, and Ikuta S performed the research; Iida H and Yamanaka N analyzed the data.
Correspondence to: Hiroya Iida, MD, Department of Surgery, Meiwa Hospital 4-31 Agenaruo-cho, Nishinomiya, Hyogo 663-8186, Japan. hiroya0001@mac.com
Telephone: +81-798-471767 Fax: +81-798-477613
Received: March 25, 2012
Revised: July 30, 2012
Accepted: August 4, 2012
Published online: November 7, 2012
Abstract

AIM: To retrospectively evaluate the effectiveness of impedance monitoring for predicting popping during radiofrequency ablation (RFA) using internally cooled electrodes.

METHODS: We reviewed 140 patients (94 males, 46 females; age range 73.0 ± 11.1 year) who underwent RFA between February 2006 and November 2008 with a modified protocol using a limited power delivery rather than a conventional one to avoid popping. All the patients provided their written informed consent, and the study was approved by the institutional review board. Intraprocedural impedances were measured for the study subjects, and the tumors were classified into three types according to the characteristics of their impedance curves: increasing, flat, or decreasing. The tumors were further sorted into seven subtypes (A-G) depending on the curvature of the impedance curve’s increase or decrease. Relative popping rates were determined for the three types and seven subtypes. A chi-square test was performed to estimate statistical significance.

RESULTS: A total of 148 nodules treated by RFA were analyzed. The study samples included 132 nodules of hepatocellular carcinoma, 14 nodules of metastatic liver cancer, and two nodules of intrahepatic cholangiocarcinoma. The numbers of nodules with each impedance curve type were as follows: 37 increasing-type nodules, 43 flat-type nodules, and 68 decreasing-type nodules. Popping occurrence rates were 24.3%, 46.5% and 64.7%, respectively. Flat-type nodules exhibited a significantly higher rate of popping compared to increasing-type nodules (P = 0.039). Decreasing-type nodules exhibited a significantly higher rate of popping compared to increasing-type nodules (P < 0.0001). Notably, nodules that showed a sharp decrease in impedance in the latter ablation period (subtype E) exhibited a significantly higher rate of popping compared to other subtypes.

CONCLUSION: Intraprocedural impedance monitoring can be a useful tool to predict the occurrence of popping during liver tumor RFA performed with internally cooled electrodes.

Keywords: Radiofrequency ablation; Internally cooled electrode; Popping; Liver; Complication