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Xu Chen

Publications and source records attributed to Xu Chen.

At least 19 recordsLinked to original sources
PubMed2026

A fitness advantage from the pLVPK plasmid fuels the global spread of a carbapenem-resistant hypervirulent Klebsiella pneumoniae high-risk clone: ST11-KL64.

BACKGROUND: The global emergence of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP), particularly the ST11-KL64 subclone acquiring pLVPK-like virulence plasmids, represents a critical public health threat. This study investigates the epidemiological dominance and molecular mechanisms underlying ST11-KL64's fitness advantage over KL47 variants. METHODS: We performed comparative genomic analysis on 43,722 K. pneumoniae genomes (2011-2022) from 112 countries, focusing on ST11-CRKP strains. Capsular typing (KL64 vs. KL47), virulence gene profiling (aerobactin, RmpADC), and plasmid stability analysis were conducted using Kleborate, RAST, and PlasmidFinder. Plasmid-chromosome interactions were characterized through hybrid assembly approaches. RESULTS: ST11-KL64 demonstrated rapid expansion post-2016, surpassing KL47 as China's dominant CRKP subtype (40.5% vs. 28.9%), with regional predominance in Zhejiang (62.3%) and Sichuan (58.7%) provinces. Notably, 94.8% of KL64 strains maintained intact pLVPK plasmids with high aerobactin carriage (60.5%), while KL47 exhibited frequent plasmid fusion (58.8% with IncFIB[pNDM-Mar]) or chromosomal integration (41.4%), resulting in lower virulence potential (27.3% aerobactin+). Genomic analysis revealed KL64's superior plasmid stability (71.2% gene retention vs. KL47's 43.6%) and clinical correlation with severe outcomes (OR = 2.34, 95%CI 1.67-3.28). CONCLUSION: The ST11-KL64 subclone's epidemiological success stems from stable pLVPK plasmid maintenance, enabling simultaneous carbapenem resistance and hypervirulence. These findings highlight the urgent need for genomic surveillance targeting plasmid-mediated virulence in CRKP outbreaks, particularly in critical care settings where horizontal gene transfer may accelerate strain evolution.

Klebsiella pneumonia↗
PubMed2026

Dietary Polyphenol Acteoside-Related Molecular Signatures in Clear Cell Renal Cell Carcinoma: Multi-Omics Profiling and Functional Validation of IMPDH1.

Clear cell renal cell carcinoma (ccRCC) is characterized by substantial metabolic and molecular heterogeneity, but the disease-relevant programs associated with acteoside, a dietary polyphenol, remain poorly understood. We integrated predicted acteoside targets with bulk, single-cell, and spatial transcriptomic data from ccRCC and combined molecular subtyping with cross-cohort machine-learning analysis. Acteoside-related signatures were preferentially enriched in malignant compartments and increased with tumor grade and stage. Consensus clustering identified two molecular subtypes with distinct biological and clinical features. C1 was associated with immune activation, metabolic activity, and more favorable survival, whereas C2 showed greater genomic instability, reduced renal epithelial differentiation, and poorer outcomes. We further benchmarked multiple machine-learning strategies and established a 10-gene prognostic model that retained predictive performance across independent cohorts, with IMPDH1 emerging as the strongest risk-associated feature. Functional experiments confirmed the biological relevance of IMPDH1: its knockdown suppressed ccRCC cell proliferation, DNA synthesis, colony formation, and migration, whereas overexpression produced the opposite effects. Together, these findings indicate that acteoside-related molecular signatures capture clinically relevant heterogeneity in ccRCC and provide a framework for linking dietary-polyphenol-related molecular space with tumor biology. The identification and functional validation of IMPDH1 further highlight its potential importance in ccRCC progression.

IMPDH1↗
PubMed2026

Pathomics-based machine learning models for predicting METTL5 expression and prognosis in lung adenocarcinoma.

BACKGROUND: METTL5, an N6-methyladenosine (m6A) RNA methyltransferase, has been implicated in tumor progression, but its prognostic value and non-invasive prediction in lung adenocarcinoma (LUAD) remain unclear. This study aimed to develop a pathomics-based machine learning model to predict METTL5 expression from histopathological images and evaluate its prognostic significance in LUAD. METHODS: A total of 327 LUAD patients from The Cancer Genome Atlas (TCGA) with matched hematoxylin and eosin (H&E) slides, transcriptomic, and clinical data were included and randomly divided into training and validation sets (7:3). Quantitative histopathological features were extracted using PyRadiomics. Feature selection was performed via maximum relevance minimum redundancy (mRMR) and recursive feature elimination (RFE), followed by construction of a Gradient Boosting Machine (GBM) model. A pathomics score (PS) was generated to assess prognostic relevance. Survival analyses, gene set variation analysis (GSVA), tumor mutational burden (TMB), immune infiltration analysis, and in vitro functional assays were conducted. RESULTS: METTL5 overexpression was independently associated with poor overall survival [hazard ratio (HR) =1.637, P=0.007]. The model achieved good predictive performance [area under the curve (AUC) =0.847 in the training set and 0.752 in the validation set]. High PS was significantly associated with worse survival and remained an independent prognostic factor (HR =1.563, P=0.03). Elevated PS correlated with altered metabolic pathways, increased TMB, and immune microenvironment changes. METTL5 knockdown reduced proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) in A549 cells. CONCLUSIONS: The pathomics-based model accurately predicts METTL5 expression and provides prognostic stratification in LUAD, supporting its potential as a practical imaging-derived biomarker.

Methyltransferase-like 5↗
PubMed2026

Resveratrol Attenuates Gemcitabine Resistance in Hepatocellular Carcinoma Cells by Inhibiting Thymidylate Synthase.

BACKGROUND: Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide. Gemcitabine (Gem) is a commonly used drug against HCC, but its efficacy is limited by the development of resistance. Resveratrol (Res), a natural polyphenol with antitumor activity, may reverse Gem resistance in HCC, although the mechanism remains unclear. METHODS: The effects of Res on the proliferation, apoptosis, cell cycle, and invasion of Hep3B and HuH-7 cells were assessed via cell counting kit-8 (CCK-8), clonogenic, flow cytometry, and Transwell assays, respectively. Potential Res targets were predicted by network pharmacology, and markers of HCC prognosis were identified from the cancer genome atlas (TCGA) data. The interaction between Res and thymidylate synthase (TYMS) was validated by molecular docking and dynamics simulation. A Gem-resistant HuH-7 cell line (HuH-7/GR) was established, and when these cells were treated with Res combined with Gem, the effect on Gem sensitivity was detected by CCK-8 assay, clonogenic assay, and flow cytometry. Finally, a subcutaneous nude mouse model of HCC was used to evaluate the in vivo effects of Res combined with Gem. RESULTS: Res inhibited HCC cell proliferation, induced apoptosis and G2/M arrest, and suppressed invasion in a concentration-dependent manner. Network pharmacology and TCGA analysis identified TYMS as an important target gene for Res. TYMS was highly expressed in HCC tissues and correlated with poor prognosis. Res treatment reduced TYMS expression, while molecular docking and simulation showed stable binding of Res to TYMS. TYMS levels were elevated in HuH-7/GR resistant cells. Res combined with Gem was found to reverse drug resistance, inhibit proliferation and colony formation, and induce apoptosis. The Res + Gem combination group showed the smallest tumor volume in the in vivo model. CONCLUSION: By attenuating Gem resistance through TYMS inhibition, Res holds promise as a clinically viable adjunct to Gem-based chemotherapy, offering a potential strategy to improve outcomes in HCC patients.

Resveratrol↗
PubMed2026

Miniature and versatile genome regulation TnpB-ωRNA toolkits facilitate cancer immunotherapy.

CRISPR‒Cas systems represent powerful tools for genome regulation. However, the large size of Cas proteins limits their efficient delivery via an adeno-associated virus (AAV), thereby restricting their clinical translation. Here, we engineer the IS200/IS605 transposon-encoded nuclease TnpB, along with its ωRNA scaffold, to create an enhanced TnpB system, which serves as a compact toolkit for gene activation, genome editing, and base editing. The gene activator enTnpBa increases expression by 2889-fold with a minimized 93 nt ωRNA and robustly activates endogenous genes in mammalian cells. We develop a single-AAV-based regimen for immune activation (AAV-ImmunAct) that delivers enTnpBa to activate CXCL9, IL-15, and IFN-γ. AAV-ImmunAct effectively enhances T cell migration and activation, increases killing of cancer cell lines and patient-derived organoids, and synergizes with anti-PD-1 therapy in humanized mice. Here, we establish enTnpB as a compact and versatile platform for genome regulation and a promising tool for cancer immunotherapy.

Humans↗
PubMed2026

TRIM49 Deficiency Stabilizes a Galectin-3/EGR1 Transcriptional Complex That Drives Invasiveness of Gastric Adenocarcinoma.

UNLABELLED: Tissue invasion is an initiating step of the cancer metastatic cascade. Unraveling the mechanisms underlying intracellular signaling pathway rewiring that activates downstream transcriptional machinery to drive invasiveness could help identify improved strategies to prevent and treat metastasis. Through an unbiased genome-wide CRISPR screen in a mouse model of gastric adenocarcinoma (GAC), an E3 ubiquitin ligase, tripartite motif-containing protein 49 (TRIM49), was identified as a potent suppressor of cancer invasiveness. In two thirds of GAC, TRIM49 expression was downregulated in invading cancer cells, in which TRIM49 deficiency correlated with deeper tumor infiltration and lymph node metastasis and was indicative of shorter overall patient survival. In multiple orthotopic GAC mouse models, TRIM49-deficient cancer cells were highly infiltrative, leading to multiorgan metastasis. Mechanistically, galectin-3, a putative regulator of cancer invasion, was stabilized in TRIM49-deficient cancer, largely because of the failure to undergo TRIM49-mediated polyubiquitination and proteasomal degradation. Consequently, galectin-3 assembled a complex with EGR1, thereby regulating transcriptional activities of a proinvasive gene module. As the galectin-3/EGR1 complex acted as a key node relaying proinvasive signaling, its disruption using GB1107, an oral galectin-3 inhibitor, suppressed tissue infiltration and metastasis of patient-derived xenografts. Taken together, a proinvasive galectin-3/EGR1 transcriptional complex was exploited by TRIM49-deficient GAC to fuel tissue invasion, representing an Achilles' heel that is potentially targetable to prevent metastasis. SIGNIFICANCE: A proinvasion galectin-3/EGR1 transcriptional complex is a therapeutic vulnerability in the highly invasive TRIM49-deficient gastric adenocarcinoma, which can be disrupted by the oral galectin-3 inhibitor GB1107 to prevent cancer spreading.

Stomach Neoplasms↗
PubMed2025

The GSA Family in 2025: A Broadened Sharing Platform for Multi-omics and Multimodal Data.

The Genome Sequence Archive family (GSA family) provides a comprehensive suite of database resources for archiving, retrieving, and sharing multi-omics data for the global academic and industrial communities. It currently comprises four distinct database members: the Genome Sequence Archive (GSA, https://ngdc.cncb.ac.cn/gsa), the Genome Sequence Archive for Human (GSA-Human, https://ngdc.cncb.ac.cn/gsa-human), the Open Archive for Miscellaneous Data (OMIX, https://ngdc.cncb.ac.cn/omix), and the Open Biomedical Imaging Archive (OBIA, https://ngdc.cncb.ac.cn/obia). Compared to its 2021 version, the GSA family has expanded significantly by introducing a new repository, the OBIA, and by comprehensively upgrading the existing databases. Notable enhancements to the existing members include broadening the range of accepted data types, strengthening quality control systems, improving the data retrieval system, and refining data-sharing management mechanisms.

Humans↗
PubMed2007

Advanced quantitative echocardiography in arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Arrhythmogenic right ventricular (RV) cardiomyopathy (ARVC) is a regional disease of the RV myocardium with variable degrees of left ventricular involvement. Three-dimensional echocardiography and Doppler tissue imaging (DTI) are new echocardiographic modalities for the evaluation of global and regional function, but the diagnostic potential remains to be assessed. METHODS: Twenty patients with previously established ARVC were evaluated by 3-dimensional echocardiography and DTI, and compared with 32 age- and sex-matched control subjects. RESULTS: Using 3-dimensional echocardiography, patients with ARVC had a decreased RV ejection fraction (0.47 +/- 0.08 vs 0.53 +/- 0.05, P < .01), and a decreased peak lateral systolic annular velocity by pulsed wave imaging of both the RV (11.9 +/- 2.6 vs 15.1 +/- 3.7 cm/s, P < .01) and the left ventricle (7.0 +/- 2.6 vs 9.5 +/- 1.9 cm/s, P < .01). DTI showed decreased regional systolic strain, but with wide variation in the measurements. CONCLUSION: Three-dimensional echocardiography identifies decreased RV ejection fraction in ARVC. Assessment of regional contractility by DTI is limited by wide variation. Echocardiographic evaluation of the longitudinal motility appears to be a sensitive marker of preclinical left ventricular involvement.

Adult↗
PubMed2006

Non-optimal TATA elements exhibit diverse mechanistic consequences.

To reveal mechanistic differences in transcription initiation between variant TATA elements, in vivo and in vitro assays of the functional activity of 14 different sequences were compared. Variant elements exhibited particular degrees of activation in vivo but universally were unable to support the -fold activation observed for an element consisting of TATAAA. Each element was classified by its functional activity for in vitro interaction with TATA-binding protein (TBP), TFIIA, and TFIIB. Certain off-consensus TATA elements form poor binding sites for TBP and this compromised interaction interferes with higher order complex formation with TFIIA and/or TFIIB. Other elements are only modestly decreased for TBP binding but dramatically affected for higher order complex formation. Another distinct category is comprised of two elements (CATAAA and TATAAG), which are not affected in the initial formation of the TBP, TFIIA-TBP, or TFIIB-TBP complexes. However, CATAAA and TATAAG are unable to form a stable TFIIA-TBP-DNA complex in vitro. Moreover, fusion of TFIIA to TBP specifically restores activity from these two elements in vivo. Taken together, these results indicate that the interplay between the sequence of the TATA element and the components of the general transcription machinery can lead to variations in the formation of functional complexes and/or the stability of these complexes. These differences offer distinct opportunities for an organism to exploit diverse steps in the regulation of gene expression depending on the precise TATA element sequence at a given gene.

Base Sequence↗
PubMed2006

Exploring predictive and reproducible modeling with the single-subject FIAC dataset.

Predictive modeling of functional magnetic resonance imaging (fMRI) has the potential to expand the amount of information extracted and to enhance our understanding of brain systems by predicting brain states, rather than emphasizing the standard spatial mapping. Based on the block datasets of Functional Imaging Analysis Contest (FIAC) Subject 3, we demonstrate the potential and pitfalls of predictive modeling in fMRI analysis by investigating the performance of five models (linear discriminant analysis, logistic regression, linear support vector machine, Gaussian naive Bayes, and a variant) as a function of preprocessing steps and feature selection methods. We found that: (1) independent of the model, temporal detrending and feature selection assisted in building a more accurate predictive model; (2) the linear support vector machine and logistic regression often performed better than either of the Gaussian naive Bayes models in terms of the optimal prediction accuracy; and (3) the optimal prediction accuracy obtained in a feature space using principal components was typically lower than that obtained in a voxel space, given the same model and same preprocessing. We show that due to the existence of artifacts from different sources, high prediction accuracy alone does not guarantee that a classifier is learning a pattern of brain activity that might be usefully visualized, although cross-validation methods do provide fairly unbiased estimates of true prediction accuracy. The trade-off between the prediction accuracy and the reproducibility of the spatial pattern should be carefully considered in predictive modeling of fMRI. We suggest that unless the experimental goal is brain-state classification of new scans on well-defined spatial features, prediction alone should not be used as an optimization procedure in fMRI data analysis.

Artifacts↗
PubMed2006

Recurrence of pulmonary vein conduction and atrial fibrillation after pulmonary vein isolation for atrial fibrillation: a randomized trial of the ostial versus the extraostial ablation strategy.

BACKGROUND: Both segmental ostial and circumferential extraostial pulmonary vein (PV) isolation have been proven effective in the treatment of atrial fibrillation (AF). However, the recurrence of AF and PV conduction after the 2 ablation strategies has never been compared in a randomized study. METHODS: A total of 100 consecutive patients (age 56 +/- 10; 71 men) with symptomatic AF (paroxysmal, 51; persistent, 49) were randomized to segmental ostial (n = 54) or circumferential extraostial (n = 46) PV isolation. A circular catheter positioned at the ostium of each target PV guided the ostial PV isolation. Extraostial PV isolation was performed by encircling the paired left and right PVs, respectively, guided by an electroanatomic mapping system. RESULTS: A total of 84% of the patients had recurrent AF after the first PV isolation procedure, showing 72% with AF and 12% with organized left atrial tachycardia. In patients undergoing reablation, all but 2 patients had recurrence of left atrium PV conduction (>95%). During a mean follow-up of 12 months without antiarrhythmic medication, 57% of patients who underwent extraostial PV isolation were free of arrhythmia symptoms compared with 31% of patients who underwent ostial PV isolation (P < .05). This difference in success rate between the 2 ablation strategies was mainly seen in patients known with persistent AF (52% and 15%, respectively; P = .02) as opposed to patients with paroxysmal AF (65% and 46%, respectively; P = .26). CONCLUSIONS: Overall, the more proximal, extraostial PV isolation was found to be superior to ostial PV isolation, especially in patients known with persistent AF. A high recurrence rate of 84% after a single complete PV isolation procedure was seen. At reablation, more than 95% had recurrence of left atrium PV conduction regardless of the procedure used, supporting the idea that complete PV isolation seems essential to prevent arrhythmia recurrences.

Aged↗
PubMed2006

The effectiveness of a high output/short duration radiofrequency current application technique in segmental pulmonary vein isolation for atrial fibrillation.

AIMS: Segmental pulmonary vein (PV) isolation by radiofrequency (RF) catheter ablation has become a curative therapy for atrial fibrillation (AF). However, the long procedure time limits the wide application of this procedure. The aim of the current study was to compare a novel ablation technique with a high power output and short application time vs. a conventional technique using a low power output and long application time. METHODS AND RESULTS: The study included 90 consecutive patients (age 53+/-10 years; 66 men). Segmental PV isolation was performed by irrigated RF catheter ablation in both groups. In the conventional group (Group 1, 45 patients), the power output was limited to 30 W with a target temperature of 50 degrees C and an RF preset duration of 120 s. In the novel group (Group 2, 45 patients), the maximum power output was preset to 45 W, with a target temperature of 55 degrees C and duration of 20 s. In Group 2, a significant reduction in the PV isolation time (127+/-57 vs. 94+/-33 min, P<0.02), mean fluoroscopy time (73+/-23 vs. 55+/-16 min, P<0.001), and radiation dose was observed. According to the application time and number, Group 2 showed a reduction in RF application time, but a higher number of RF applications were required for creation of complete PV isolation. During a mean follow-up of 15+/-7 months, a total of 74% of patients in Group 1 and 76% of patients in Group 2 demonstrated stable SR. CONCLUSION: Segmental PV isolation using a high power output and short application time is safe and effective in PV isolation in patients with AF. This technique can significantly reduce the procedure and fluoroscopy time compared with a low-power output technique.

Atrial Fibrillation↗
PubMed2006

[Survey of contraceptive knowledge in married couples at reproductive age in 5 Chinese cities].

OBJECTIVE: To survey the married couples at reproductive age for contraceptive knowledge in 5 Chinese cities. METHODS: The data derived from a questionnaire-based research conducted in 2002 on family planning among married couples in 5 Chinese cities were statistically analyzed. RESULTS: The total rate of good contraceptive knowledge was 70.10% in the couples. Among all the contraceptive measures, condom use was the most familiar one. The understanding of contraceptive knowledge in couples working in official departments and educational institutes was better than that among the couples working in common enterprises, affected by such factors as gender, geographic regions, educational background and willingness of child-bearing. CONCLUSION: The married couples in the Chinese cities have generally good understanding of contraceptive knowledge, which can be affected by different factors among different populations.

Adult↗
PubMed2006

[Experimental study of the inhibitory effects of Chelidonium majus L. extractive on Streptococcus mutans in vitro].

PURPOSE: To study the inhibitory effects of Chelidonium majus L. extractive on the growth of Streptococcus mutans in vitro, and to explore its mechanism in caries prevention. METHODS: Streptococcus mutans 25175 was chosen as the experimental bacterium. The Chelidonium majus L. extractives chelidonine and chelerythrine were double diluted to different concentrations by two-fold dilution. The inhibitory effect of Streptococcus mutans was measured by slip diffusion method. The minimal inhibitory concentration(MIC) was also determined. 0.16% liquor hibitane was used as positive control. Spearman correlation was used for statistical analysis. RESULTS: Inhibition zone of Streptococcus mutans appeared in some concentration of chelerythrine, but no inhibition zone in each concentration of chelidonine. The MIC of chelerythrine was 0.78 mg/ml which determined by liquid culture medium. The concentration of chelerythrine was highly related to the inhibitory zone of Streptococcus mutans (r=0.99, P<0.01). CONCLUSION: The antibacterial activity of Chelidonium majus L. extractive chelerythrine on Streptococcus mutans was significant,and the antibacterial activity of the concentration 100 mg/ml was higher than that of 0.16% liquor hibitane (19.4 mm), indicating that chelerythrine can be used as an agent for prevention of dental caries.

Anti-Bacterial Agents↗
PubMed2006

[kgp genotypes of Porphyromonas gingivalis in subgingival plaque in puberty gingivitis].

OBJECTIVE: To assess the prevalence of specific kgp genotypes in puberty gingivitis and investigate their possible association with disease severity. METHODS: Subgingival plaque samples were collected from 72 pubertal children aged from 14 to 17 years, which were divided into two groups, gingivitis group and healthy (control) group. Clinical parameters were recorded beforehand. PCR technique was used to amplify the region encoding the catalytic domain of gingipain K (KGP). The PCR products were digested with restriction enzymes Mse I. RESULTS: The kgp-A genotype was digested in fragments of 102 bp, 288 bp and 402 bp, and kgp-B genotype was unrestricted with 792 bp. Virulent strain P. gingivalis W83 was manifested by kgp-A genotype while a virulent strain P. gingivalis ATCC 33277 was manifested by kgp-B genotype. All P. gingivalis positive subjects were subgingivally colonized by only one kgp genotype. The prevalence of kgp-A genotype in puberty gingivitis group and gingival healthy group was 79.0% and 22.2% respectively. The distribution differences of genotypes between the two groups were statistically different (P = 0.028). There was no statistically significant difference in the clinical parameters between pubertal subjects harboring P. gingivalis of kgp-A genotype and kgp-B genotype (P > 0.05). CONCLUSIONS: Most subjects with puberty gingivitis were harbored by the same kgp genotype as that of virulent strain P. gingivalis W83. It may be necessary to continue to monitor individuals who are positive for P. gingivalis of kgp-A genotype since their risk of developing periodontal diseases may be increased in the future.

Adolescent↗
PubMed2005

Predictive value of electrocorticography in epilepsy patients with unilateral hippocampal sclerosis undergoing selective amygdalohippocampectomy.

The purpose of this study was to evaluate the predictive value of intraoperative electro-corticography (ECoG) in patients with unilateral hippocampal sclerosis (HS) undergoing transsylvian selective amygdalohippocampectomy (sAHE). ECoG was recorded before and after resection in 22 patients with medication-resistant mesial temporal lobe epilepsy. The sAHE was performed, regardless of ECoG findings. ECoG findings recorded from the mesiobasal temporal lobe (MTL) and lateral temporal lobe (LTL) before and after the sAHE were correlated with seizure outcome 12 months later. Ten patients had right-sided and 12 left-sided HS. Average age was 37.1 years. Pre-resection spikes were restricted to the MTL in 11 patients and to the LTL in one. In three patients spikes were recorded from MTL and LTL and in seven no spikes were recorded before the resection. Fifteen patients (68%) remained completely seizure-free and 19 (86%) were in Engel's class I post-operatively. Patients with pre-resection spikes restricted to the MTL (n = 11) remained seizure-free more frequently (9/11, 82%) compared with other patients (6/11, 55%; P = 0.36). Pre-resection ECoG may be helpful in the prediction of seizure outcome in patients undergoing sAHE for mesial temporal lobe epilepsy. A larger study including more than 100 patients is needed to determine the predictive value of ECoG in patients with mesial temporal lobe epilepsy.

Adolescent↗
PubMed2005

Indication of the radiofrequency induced lesion size by pre-ablation measurements.

BACKGROUND: During radiofrequency ablation of arrhythmias tissue heating and hence lesion size depend on electrode-tissue contact and cooling of the electrode tip caused by cavitary blood flow. These factors are unique and unknown for each catheter placement in the beating heart. A tool for assessing these factors prior to ablation may indicate the lesion size which will be obtained for any given catheter position. METHODS AND RESULTS: Radiofrequency ablation was performed in vitro on strips of left ventricular porcine myocardium during two different levels of convective cooling (0 or 0.1 m/s), two different contact pressures (10 or 30 g) and parallel or perpendicular electrode-tissue orientation using 7F 4 mm tip catheters. Prior to ablation the impedance rise (DeltaIMP) caused by the obtained contact and the temperature rise with a 0.6 W 5 s test pulse (DeltaT) were measured. Subsequently, during unchanged conditions, radiofrequency ablation was performed as either temperature-controlled, power-controlled or irrigated tip ablation and lesion size was determined. DeltaIMP increased significantly (P < 0.05) by improved contact, whereas it was not affected by convective cooling. DeltaT was significantly increased by increasing contact pressure (P < 0.05) and significantly decreased by increased cooling (P < 0.001). DeltaT was not systematically affected by electrode orientation. The product of DeltaT and DeltaIMP showed a significant correlation between the obtained lesion size and power output for temperature-controlled and between lesion size and tip temperature for power-controlled ablation (P < 0.001). CONCLUSIONS: Pre-ablation measurement of DeltaIMP and DeltaT can indicate the lesion size resulting after ablation in temperature-controlled, power-controlled and irrigated ablation in vitro, since DeltaT reflects cavitary cooling and to a smaller extent electrode-tissue contact, and DeltaIMP reflects only electrode-tissue contact.

Animals↗