Predicting Safe Liver Resection Volume for Major Hepatectomy Using Artificial Intelligence.

(1) Background: Advancements in the field of liver surgery have led to a critical need for precise estimations of preoperative liver function to prevent post-hepatectomy liver failure (PHLF), a significant cause of morbidity and mortality. This study introduces a novel application of artificial intelligence (AI) in determining safe resection volumes according to a patient's liver function in major hepatectomies. (2) Methods: We incorporated a deep learning approach, incorporating a unique liver-specific loss function, to analyze patient characteristics, laboratory data, and liver volumetry from computed tomography scans of 52 patients. Our approach was evaluated against existing machine and deep learning techniques. (3) Results: Our approach achieved 68.8% accuracy in predicting safe resection volumes, demonstrating superior performance over traditional models. Furthermore, it significantly reduced the mean absolute error in under-predicted volumes to 23.72, indicating a more precise estimation of safe resection limits. These findings highlight the potential of integrating AI into surgical planning for liver resections. (4) Conclusion: By providing more accurate predictions of safe resection volumes, our method aims to minimize the risk of PHLF, thereby improving clinical outcomes for patients undergoing hepatectomy.

Outcomes of Pure Laparoscopic Living Donor Right Hepatectomy at a Small-Volume Center.

OBJECTIVES: Laparoscopic liver donor surgery is a technically difficult and demanding procedure. Our aim was toevaluate its feasibility at an established transplant center. Although our hospital is a small-volume center with <20 liver transplants per year, laparoscopic donor surgery has been performed regularly. In this study, we have reported our experiences with laparoscopic donor right hepa-tectomy and its outcomes. MATERIALS AND METHODS: Between May 2014 and March 2021, 26 deceased donor liver transplants and 37 living donor liver transplants, approved by the Korean Network for Organ Sharing, were performed at out center. From these, we reviewed the medical records, including clinical and demographic characteristics and operative outcomes, of 3 living donors who under-went pure laparoscopic donor right hepatectomy and their recipients. RESULTS: Each of the 3 laparoscopic donor right hepatectomies took over 10 hours with the prolonged Pringle maneuver time and warm ischemic time. However, there were no significant events during surgery or critical postoperative complications. In the recipients, posttransplant complications included middle hepatic vein obstruction, postoperative bleeding, bile leak, septic shock, and primary nonfunction of the graft. We managed and resolved these complications using various approaches, including retransplant, and all 3 recipients recovered and survived. CONCLUSIONS: Laparoscopic donor right hepatectomy had a relatively long operative time at our small-volume center. We believe that successful laparoscopic donor hepatectomy is possible if the donor is selected appropriately according to the center's experiences and there are constant efforts to overcome the learning curve.

Usefulness of External Biliary Stent Buried Suture for Reducing Stent-Related Complications In Liver Transplantation.

BACKGROUND: External bile stents may be used to prevent biliary complications. However, the external biliary stent itself has a risk of complications. This study evaluated the frequency and treatment of complications associated with external bile stent. METHODS: From May 2015 to September 2019, 18 deceased donor liver transplantations (DDLTs) and 25 living donor liver transplantations (LDLTs) were performed. We retrospectively reviewed these patients' demographic profiles, type of transplantation and presence of biliary complications, external bile stent-related complications, and treatment results. RESULTS: Overall biliary complications occurred in 12 patients (27.9%): 3 strictures (6.9%), 2 leakages (4.6%), and 7 external bile stent-related complications (16.2%). Among the 7, 4 were self-removal or stent fractures at home, and 2 occurred after removal by a physician. One patient had ileus with peritonitis. Local peritonitis was controlled by antibiotics and fluid therapy, but 1 patient needed an operation because of intestinal obstruction with recurrent local peritonitis. All biliary complications occurred in LDLT, and external biliary stent-related complications also occurred only in LDLT, not in DDLT (P = .014). Interestingly, only 1 of 7 external bile stent-related complications occurred after we adopted the stent buried suture technique on the duodenum (P = .062). CONCLUSIONS: External bile stent-related complications were higher in LDLT than in DDLT. When performing external bile stent implantation, the stent buried suture technique will help reduce stent-related complications, especially in LDLT.

Association between endotoxin levels in dust from indoor swine housing environments and the immune responses of pigs.

Indoor animal husbandry environments are inevitably contaminated with endotoxins. Endotoxin exposure is associated with various inflammatory illnesses in animals. This cross-sectional study evaluated the relationship between the degree of endotoxin exposure and the cellular and humoral immune profiles of fattening pigs. Blood samples were taken from the jugular vein of 47 pigs from ten pig farms in Korea. Whole blood cell counts and plasma immunoglobulin (Ig) classes were determined. Peripheral-blood mononuclear cells were stimulated in vitro with concanavalin A for 48 h, and cytokines released into culture supernatants were measured. The barns in which the pigs lived were assessed for endotoxin levels in the total and respirable dust by using the limulus amebocyte lysate kinetic QCL method. Low and high endotoxin exposures were defined as ≤ 30 and ＞ 30 EU/m³, respectively. Compared to pigs with low endotoxin exposure (n = 19), highly exposed pigs (n = 28) had higher circulating neutrophil and lymphocyte (particularly B cells) counts, IgG and IgE levels, interferon-gamma (IFNγ) and interleukin (IL)-4 productions, and lower IgA levels and tumor necrosis factor-alpha (TNFα) production. The IL-4, IFNγ, and TNFα levels significantly correlated with endotoxin level and/or pig age. Constant exposure of pigs to high levels of airborne endotoxins can lead to aberrant immune profiles.

Epizootiological characteristics of viable bacteria and fungi in indoor air from porcine, chicken, or bovine husbandry confinement buildings.

Microorganisms found in bioaerosols from animal confinement buildings not only foster the risk of spreading diseases among livestock buildings, but also pose health hazards to farm workers and nearby residents. This study identified the various microorganisms present in the air of swine, chicken, and cattle farms with different kinds of ventilation conditions in Korea. Microbial air samples were collected onto Petri dishes with bacterial or fungal growth media using a cascade impactor. Endotoxin levels in total dust were determined by the limulus amebocyte lysate kinetic QCL method. Prevalent Gram-positive bacteria were Staphylococcus (S.) lentus, S. chromogenes, Bacillus (B.) cereus, B. licheniformis, and Enterococcus faecalis, while the dominant fungi and Gram-negative bacteria were Candida albicans and Sphingomonas paucimobilis, respectively. Considering no significant relationship between the indoor dust endotoxin levels and the isolation of Gram-negative bacteria from the indoor air, monitoring the indoor airborne endotoxin level was found to be also critical for risk assessment on health for animals or workers. The present study confirms the importance of microbiological monitoring and control on animal husbandry indoor air to ensure animal and worker welfare.

Performance standard-based validation study for local lymph node assay: 5-bromo-2-deoxyuridine-flow cytometry method.

Local lymph node assay: 5-bromo-2-deoxyuridine-flow cytometry method (LLNA: BrdU-FCM) is a modified non-radioisotopic technique with the additional advantages of accommodating multiple endpoints with the introduction of FCM, and refinement and reduction of animal use by using a sophisticated prescreening scheme. Reliability and accuracy of the LLNA: BrdU-FCM was determined according to OECD Test Guideline (TG) No. 429 (Skin Sensitization: Local Lymph Node Assay) performance standards (PS), with the participation of four laboratories. Transferability was demonstrated through successfully producing stimulation index (SI) values for 25% hexyl cinnamic aldehyde (HCA) consistently greater than 3, a predetermined threshold, by all participating laboratories. Within- and between-laboratory reproducibility was shown using HCA and 2,4-dinitrochlorobenzene, in which EC2.7 values (the estimated concentrations eliciting an SI of 2.7, the threshold for LLNA: BrdU-FCM) fell consistently within the acceptance ranges, 0.025-0.1% and 5-20%, respectively. Predictive capacity was tested using the final protocol version 1.3 for the 18 reference chemicals listed in OECD TG 429, of which results showed 84.6% sensitivity, 100% specificity, and 88.9% accuracy compared with the original LLNA. The data presented are considered to meet the performance criteria for the PS, and its predictive capacity was also sufficiently validated.

Predictive capacity of a non-radioisotopic local lymph node assay using flow cytometry, LLNA:BrdU-FCM: Comparison of a cutoff approach and inferential statistics.

In order for a novel test method to be applied for regulatory purposes, its reliability and relevance, i.e., reproducibility and predictive capacity, must be demonstrated. Here, we examine the predictive capacity of a novel non-radioisotopic local lymph node assay, LLNA:BrdU-FCM (5-bromo-2'-deoxyuridine-flow cytometry), with a cutoff approach and inferential statistics as a prediction model. 22 reference substances in OECD TG429 were tested with a concurrent positive control, hexylcinnamaldehyde 25%(PC), and the stimulation index (SI) representing the fold increase in lymph node cells over the vehicle control was obtained. The optimal cutoff SI (2.7≤cutoff <3.5), with respect to predictive capacity, was obtained by a receiver operating characteristic curve, which produced 90.9% accuracy for the 22 substances. To address the inter-test variability in responsiveness, SI values standardized with PC were employed to obtain the optimal percentage cutoff (42.6≤cutoff <57.3% of PC), which produced 86.4% accuracy. A test substance may be diagnosed as a sensitizer if a statistically significant increase in SI is elicited. The parametric one-sided t-test and non-parametric Wilcoxon rank-sum test produced 77.3% accuracy. Similarly, a test substance could be defined as a sensitizer if the SI means of the vehicle control, and of the low, middle, and high concentrations were statistically significantly different, which was tested using ANOVA or Kruskal-Wallis, with post hoc analysis, Dunnett, or DSCF (Dwass-Steel-Critchlow-Fligner), respectively, depending on the equal variance test, producing 81.8% accuracy. The absolute SI-based cutoff approach produced the best predictive capacity, however the discordant decisions between prediction models need to be examined further.

Altered expression levels of neurodevelopmental proteins in fetal brains of BTBR T+tf/J mice with autism-like behavioral characteristics.

Autism is a brain developmental disorder with characteristics of social interaction defects, language and communication dysfunction, and repetitive behavior. Occurrence of autism is continuously increasing, but the cause of autism is not clearly defined. Genetic linkage or environmental factors were proposed as sources for pathogenesis of autism. BTBR T+tf/J (BTBR) mice were reported as an appropriate animal model for autism investigation because of their similarities in behavioral abnormalities with human autistic subjects. The aim of this study was to evaluate expression levels of proteins involved with brain development at fetal stage of BTBR mice. FVB/NJ mice were used as a control strain because of their social behaviors. Level of fetal brain immunoglobulin (Ig) G deposit was also evaluated. Fetal brains were obtained at d 18 of gestational period. Thirty-one and 27 fetuses were obtained from 3 pregnant BTBR and FVB dams, respectively. The level of glial fibrillary acidic protein expression was significantly lower in fetal brains of BTBR than FVB/NJ mice. Expression of brain-derived neurotrophic factor and myelin basic protein was significantly more upregulated in BTBR than in FVB/NJ mice. No significant difference was obtained for nerve growth factor between the two strains. Levels of IgG isotypes deposited in fetal brain of BTBR mice were significantly higher than in FVB mice except for IgG1. Overall, these results suggest that prenatal alterations in expression of various fetal brain proteins may be implicated in aberrant behavioral characteristics of BTBR mice.

Appraisal of within- and between-laboratory reproducibility of non-radioisotopic local lymph node assay using flow cytometry, LLNA:BrdU-FCM: comparison of OECD TG429 performance standard and statistical evaluation.

Mouse local lymph node assay (LLNA, OECD TG429) is an alternative test replacing conventional guinea pig tests (OECD TG406) for the skin sensitization test but the use of a radioisotopic agent, (3)H-thymidine, deters its active dissemination. New non-radioisotopic LLNA, LLNA:BrdU-FCM employs a non-radioisotopic analog, 5-bromo-2'-deoxyuridine (BrdU) and flow cytometry. For an analogous method, OECD TG429 performance standard (PS) advises that two reference compounds be tested repeatedly and ECt(threshold) values obtained must fall within acceptable ranges to prove within- and between-laboratory reproducibility. However, this criteria is somewhat arbitrary and sample size of ECt is less than 5, raising concerns about insufficient reliability. Here, we explored various statistical methods to evaluate the reproducibility of LLNA:BrdU-FCM with stimulation index (SI), the raw data for ECt calculation, produced from 3 laboratories. Descriptive statistics along with graphical representation of SI was presented. For inferential statistics, parametric and non-parametric methods were applied to test the reproducibility of SI of a concurrent positive control and the robustness of results were investigated. Descriptive statistics and graphical representation of SI alone could illustrate the within- and between-laboratory reproducibility. Inferential statistics employing parametric and nonparametric methods drew similar conclusion. While all labs passed within- and between-laboratory reproducibility criteria given by OECD TG429 PS based on ECt values, statistical evaluation based on SI values showed that only two labs succeeded in achieving within-laboratory reproducibility. For those two labs that satisfied the within-lab reproducibility, between-laboratory reproducibility could be also attained based on inferential as well as descriptive statistics.

Relationship between chicken cellular immunity and endotoxin levels in dust from chicken housing environments.

Hazardous biochemical agents in animal husbandry indoor environments are known to promote the occurrence of various illnesses among workers and animals. The relationship between endotoxin levels in dust collected from chicken farms and various immunological markers was investigated. Peripheral blood was obtained from 20 broiler chickens and 20 laying hens from four different chicken farms in Korea. Concentrations of total or respirable dust in the inside the chicken farm buildings were measured using a polyvinyl chloride membrane filter and mini volume sampler. Endotoxin levels in the dust were determined by the Limulus Amebocyte Lysate Kinetic method. Interferon-γ production by peripheral blood mononuclear cells stimulated with concanavalin A was significantly lower in broilers or layers from the farms with higher endotoxin concentrations than the chickens from the farms with lower endotoxin levels. An opposite pattern was observed for plasma cortisol concentrations with higher cortisol levels found in chickens from the farms with higher endotoxin levels. When peripheral lymphocytes were examined, the percentage of CD3(-)Ia(+) B cells was lower in layers from farms with higher endotoxin levels than those from locations with lower endotoxin levels. Overall, these results suggest a probable negative association between dust endotoxin levels and cell-mediated immunity in chickens.

Hydroxyapatite-coated magnesium implants with improved in vitro and in vivo biocorrosion, biocompatibility, and bone response.

Magnesium and its alloys are candidate materials for biodegradable implants; however, excessively rapid corrosion behavior restricts their practical uses in biological systems. For such applications, surface modification is essential, and the use of anticorrosion coatings is considered as a promising avenue. In this study, we coated Mg with hydroxyapatite (HA) in an aqueous solution containing calcium and phosphate sources to improve its in vitro and in vivo biocorrosion resistance, biocompatibility and bone response. A layer of needle-shaped HA crystals was created uniformly on the Mg substrate even when the Mg sample had a complex shape of a screw. In addition, a dense HA-stratum between this layer and the Mg substrate was formed. This HA-coating layer remarkably reduced the corrosion rate of the Mg tested in a simulated body fluid. Moreover, the biological response, including cell attachment, proliferation and differentiation, of the HA-coated samples was enhanced considerably compared to samples without a coating layer. The preliminary in vivo experiments also showed that the biocorrosion of the Mg implant was significantly retarded by HA coating, which resulted in good mechanical stability. In addition, in the case of the HA-coated implants, biodegradation was mitigated, particularly over the first 6 weeks of implantation. This considerably promoted bone growth at the interface between the implant and bone. These results confirmed that HA-coated Mg is a promising material for biomedical implant applications.

Mechanical strength and biocompatibility of ultrafine-grained commercial purity titanium.

The effect of grain refinement of commercial purity titanium by equal channel angular pressing (ECAP) on its mechanical performance and bone tissue regeneration is reported. In vivo studies conducted on New Zealand white rabbits did not show an enhancement of biocompatibility of ECAP-modified titanium found earlier by in vitro testing. However, the observed combination of outstanding mechanical properties achieved by ECAP without a loss of biocompatibility suggests that this is a very promising processing route to bioimplant manufacturing. The study thus supports the expectation that commercial purity titanium modified by ECAP can be seen as an excellent candidate material for bone implants suitable for replacing conventional titanium alloy implants.

Hydroxyapatite/poly(epsilon-caprolactone) double coating on magnesium for enhanced corrosion resistance and coating flexibility.

Hydroxyapatite was deposited on pure magnesium (Mg) with a flexible poly(ε-caprolactone) interlayer to reduce the corrosion rate of Mg and enhance coating flexibility. The poly(ε-caprolactone) interlayer was uniformly coated on Mg by a spraying method, followed by hydroxyapatite deposition on the poly(ε-caprolactone) using an aerosol deposition method. In scanning electron microscopy observations, inorganic/organic composite-like structure was observed between the hydroxyapatite and poly(ε-caprolactone) layers, resulting from the collisions of hydroxyapatite particles into the poly(ε-caprolactone) matrix at the initial stage of the aerosol deposition. The corrosion resistance of the coated Mg was examined using potentiodynamic polarization tests. The hydroxyapatite/poly(ε-caprolactone) double coating remarkably improved the corrosion resistance of Mg in Hank's solution. In the in vitro cell tests, the coated Mg showed better cell adhesion compared with the bare Mg due to the reduced corrosion rate and enhanced biocompatibility. The stability and flexibility of hydroxyapatite/poly(ε-caprolactone) double coating was investigated by scanning electron microscopy inspections after the coated Mg was deformed. The hydroxyapatite coating on the poly(ε-caprolactone) interlayer revealed enhanced coating stability and flexibility without cracking or delamination during bending and stretching compared with the hydroxyapatite single coating. These results demonstrated that the hydroxyapatite/poly(ε-caprolactone) double coating significantly improved the surface corrosion resistance of Mg and enhanced coating flexibility for use of Mg as a biodegradable implant.

Use of a poly(ether imide) coating to improve corrosion resistance and biocompatibility of magnesium (Mg) implant for orthopedic applications.

This study investigated the utility of poly(ether imide) (PEI) coating for improving the corrosion resistance and biocompatibility of magnesium (Mg) implants for orthopedic application. In particular, the microstructure of the PEI coating layers was controlled by the adjustment of the temperature used to dry the spin-coated wet PEI films. When a wet PEI film was dried at 4°C, a relatively thick and porous coating layer was achieved as a result of an extensive exchange of the solvent with water in a moist environment. In contrast, when a wet PEI film was dried at 70°C, a relatively thin and dense layer was created due to the faster evaporation of the solvent with a negligible exchange of the solvent with water. The porous PEI coating layer showed higher stability than did the dense one when immersed in a simulated body fluid (SBF), which was presumably attributed to the formation of chemical bonding between the PEI and the Mg substrate. Both the porous and the dense PEI coated Mg specimens showed significantly improved in vitro biocompatibility, which were assessed in terms of cell attachment, proliferation and differentiation. However, interestingly, the dense PEI coating layer showed greater cell proliferation and differentiation than did the porous layer. .

Fibrous membrane of nano-hybrid poly-L-lactic acid/silica xerogel for guided bone regeneration.

Nanofibrous membranes, consisting of a poly(L-lactic acid) (PLLA)-silica xerogel hybrid material, were successfully fabricated from a hybrid sol using the electrospinning technique for guided bone regeneration (GBR) application. These hybrid nanofibers exhibited a homogeneous and continuous morphology, with a nano-sized dispersed silica xerogel phase in the PLLA fiber matrix. The mechanical properties, such as the tensile strength and the elastic modulus, were improved as the silica xerogel content increased up to 40%. All of the hybrid membranes exhibited highly hydrophilic surfaces and good proliferation levels. After culturing for 13 days, the cells that were cultured on the hybrid membranes exhibited a significantly higher ALP activity compared to the pure PLLA membrane. Moreover, the in vivo animal experiments that used the rat calvarial defect model revealed a remarkably improved bone regeneration ability for the hybrid membrane compared to pure PLLA. These results demonstrated the feasibility of these hybrid membranes for efficient GBR.

Enhancing biocompatibility and corrosion resistance of Mg implants via surface treatments.

Oxide coating layers were formed on a pure magnesium (Mg) substrate through anodization and micro-arc oxidation (MAO) in order to enhance the biocompatibility and reduce the degradation rate. A thin, smooth MgO coating layer was formed after the anodization. On the other hand, when the Mg was treated using the MAO process, a relatively thick, rough MgO layer was formed. The corrosion properties were investigated using electrochemical and ion release tests in a simulated body fluid. Both the anodization and the MAO treatment enhanced the corrosion resistance of the Mg specimens. However, the MgO layers that formed on the surface were not stable enough to render favorable environments for cell growth. The anodized and MAO-treated specimens were post-treated in a cell-culturing medium in order to improve the stability of the coating layer. The biocompatibility was evaluated using in vitro cell tests, including cell attachment, DNA measurement, and alkaline phosphatase (ALP) activity tests. The DNA levels of the surface-treated Mg were about 6-10 times higher than the bare Mg. The ALP activity levels were also more than double after either the anodization or the MAO followed by the post-treatments. These results demonstrated that the biocompatibility and the corrosion resistance of Mg were significantly improved by the series of surface treatments.

Hydroxyapatite coating on magnesium with MgF2 interlayer for enhanced corrosion resistance and biocompatibility.

Hydroxyapatite (HA) was coated onto pure magnesium (Mg) with an MgF(2) interlayer in order to reduce the surface corrosion rate and enhance the biocompatibility. Both MgF(2) and HA were successfully coated in sequence with good adhesion properties using the fluoride conversion coating and aerosol deposition techniques, respectively. In a simulated body fluid (SBF), the double layer coating remarkably enhanced the corrosion resistance of the coated Mg specimen. The in vitro cellular responses of the MC3T3-E1 pre-osteoblasts were examined using a cell proliferation assay and an alkaline phosphatase (ALP) assay, and these results demonstrated that the double coating layer also enhanced cell proliferation and differentiation levels. In the in vivo study, the HA/MgF(2) coated Mg corroded less than the bare Mg and had a higher bone-to-implant contact (BIC) ratio in the cortical bone area of the rabbit femora 4 weeks after implantation. These in vitro and in vivo results suggested that the HA coated Mg with the MgF(2) interlayer could be used as a potential candidate for biodegradable implant materials.

In vitro/in vivo biocompatibility and mechanical properties of bioactive glass nanofiber and poly(epsilon-caprolactone) composite materials.

In this study, a poly(epsilon-caprolactone) (PCL)/bioactive glass (BG) nanocomposite was fabricated using BG nanofibers (BGNFs) and compared with an established composite fabricated using microscale BG particles. The BGNFs were generated using sol-gel precursors via the electrospinning process, chopped into short fibers and then incorporated into the PCL organic matrix by dissolving them in a tetrahydrofuran solvent. The biological and mechanical properties of the PCL/BGNF composites were evaluated and compared with those of PCL/BG powder (BGP). Because the PCL/BG composite containing 20 wt % BG showed the highest level of alkaline phosphatase (ALP) activity, all evaluations were performed at this concentration except for that of the ALP activity itself. In vitro cell tests using the MC3T3 cell line demonstrated the enhanced biocompatibility of the PCL/BGNF composite compared with the PCL/BGP composite. Furthermore, the PCL/BGNF composite showed a significantly higher level of bioactivity compared with the PCL/BGP composite. In addition, the results of the in vivo animal experiments using Sprague-Dawley albino rats revealed the good bone regeneration capability of the PCL/BGNF composite when implanted in a calvarial bone defect. In the result of the tensile test, the stiffness of the PCL/BG composite was further increased when the BGNFs were incorporated. These results indicate that the PCL/BGNF composite has greater bioactivity and mechanical stability when compared with the PCL/BG composite and great potential as a bone regenerative material.

[Prognostic factors for survival in patients with hepatocellular carcinoma after radiofrequency ablation].

BACKGROUND/AIMS: Currently there is no consensus on which staging system is the best in predicting the survival of patients with hepatocellular carcinoma (HCC). The aim of this study was to identify independent factors to predict survival and to compare 4 available prognostic staging systems in patients with early HCC after radiofrequency ablation. METHODS: We retrospectively studied 100 Korean patients with early HCC. Prognostic factors for survival were analysed by univariate and multivariate analysis using the Kaplan-Meier method and Cox proportional hazard regression models. Okuda, Cancer of the Liver Italian Program (CLIP), TNM and Japanese integrated staging score (JIS score) were evaluated before the treatments. RESULTS: Overall survival rates of 12, 24 and 36 months were 89%, 76%, and 64% respectively and the mean survival duration was 45 months. Multivariable analysis showed that albumin, total bilirubin and size of tumor were independent prognostic factors. Multivariate analysis showed that TNM and JIS score staging systems were significant staging systems for the prediction of prognosis. CONCLUSIONS: Both TNM and JIS score are more effective than the Okuda and CLIP staging systems in stratifying patients into different risk groups with early HCC. However, JIS score gives better prediction of prognosis in patients with HCC after radiofrequency ablation.