Biomedical subjects

X Chen

Publications and source records attributed to X Chen.

At least 919 records · Page 51Linked to original sources

PubMed1998

Ramipril-induced delayed myocardial protection against free radical injury involves bradykinin B2 receptor-NO pathway and protein synthesis.

1. The aim of the present study was to examine whether ramipril induces delayed myocardial protection against free radical injuries ex vivo and to determine the possible role of the bradykinin B2-nitric oxide (NO) pathway, prostaglandins(PGs) and protein synthesis in this delayed adaptive response. 2. Rats were pretreated with ramipril (10 or 50 microg kg(-1), i.v.) and hearts were isolated after 24, 48 and 72 h. Langendorff hearts were subjected to 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical-induced injury. 3. Left ventricular developed pressure (LVDP) and its maximal increase velocity (+ dP/dtmax), coronary flow (CF), heart rate (HR), lactate dehydrogenase (LDH) in coronary effluent and thiobarbituric acid reactive substances (TBARS) in the myocardium were measured. 4. The results showed that in the DPPH control group, 20 min after free radical-induced injury, LVDP, +dP/dtmax, CF, HR declined, whereas TBARS and LDH increased significantly. The above cardiac function parameters were significantly improved in RAM-pretreated rats after 24 and 48 h. 5. Pretreatment with HOE 140, the selective bradykinin B2 receptor antagonist, NG-nitro-L-arginine, the NO synthase inhibitor, and actinomycin D, the RNA transcription inhibitor, prior to ramipril injection abolished the beneficial effects of ramipril at 24 h while indomethacin, a cyclooxygenase inhibitor, pretreatment had no effect on ramipril-induced delayed protection. 6. In conclusion, ramipril induces delayed myocardial protection against free radical injury in the rat heart. This delayed protection was sustained for 48 h, is associated with the bradykinin B2 receptor-NO pathway and depends on protein but not prostaglandin synthesis.

Animals↗

PubMed1998

Composition of peripheral blood lymphocyte populations during different stages of chronic infection with hepatitis B virus.

To characterize the immunological populations associated with different stages of chronic infection with hepatitis B virus (HBV), we performed flow cytometric analyses on the peripheral blood leucocytes of 29 patients with various forms of chronic hepatitis B. The clinical spectrum of the patients ranged from asymptomatic infections, in the presence of high virus production, to intermittent or recurrent exacerbations of liver injury alternating with relatively normal liver function. Patients with partial resolution of disease who experienced an initial acute flare followed by prolonged seroconversion showed decreased percentages of CD3+ cells during the seroconversion phase when levels of serum alanine transferase (ALT) had normalized. These CD3+ cells were predominantly CD4+ cells bearing the alpha beta+ T-cell receptor (TCR). In addition, we saw an increase in CD4+ and CD8+ cells bearing the gamma delta TCR in those patients who had seroconverted. No significant differences were seen between any of the groups with respect to percentage of cells with a naive (CD45RA) or memory (CD45RO) phenotype, or of cells displaying the activation markers CD38, HLA-DR or CD57. Longitudinal analyses of 15 patients failed to show any consistent pattern of changes in the immunophenotypic profile during acute flares and their resolution. Our results indicate that the turnover of circulating T lymphocytes during the apparent quiescent phase of chronic infections is higher than that during acute exacerbations, suggesting an active immunosurveillance role of T-cell subpopulations in maintaining low virus levels during seroconversion.

Adolescent↗

PubMed1998

Solution structures of the Huntington's disease DNA triplets, (CAG)n.

Highly polymorphic DNA triplet repeats, (CAG)n, are located inside the first exon of the Huntington's disease gene. Inordinate expansion of this repeat is correlated with the onset and progression of the disease. NMR spectroscopy, gel electrophoresis, digestion by single-strand specific P1 enzyme, and in vitro replication assay have been used to investigate the structural basis of (CAG)n expansion. Nondenaturing gel electrophoresis and 1D 1H NMR studies of (CAG)5 and (CAG)6 reveal the presence of hairpins and mismatched duplexes as the major and minor populations respectively. However, at high DNA concentrations (i.e., 1.0-2.0 mM that is typically required for 2D NMR experiments) both (CAG)5 and (CAG)6 exist predominantly in mismatched duplex forms. Mismatched duplex structures of (CAG)5 and (CAG)6 are useful, because they adequately model the stem of the biologically relevant hairpins formed by (CAG)n. We, therefore, performed detailed NMR spectroscopic studies on the duplexes of (CAG)5 and (CAG)6. We also studied a model duplex, (CGCAGCG)2 that contains the underlined building block of the duplex. This duplex shows the following structural characteristics: (i) all the nucleotides are in (C2'-endo, anti) conformations, (ii) mismatched A x A base pairs are flanked by two Watson-Crick G x C base pairs and (iii) A x A base pairs are stably stacked (and intra-helical) and are formed by a single N6-H--N1 hydrogen bond. The nature of A x A pairing is confirmed by temperature-dependent HMQC and HMQC-NOESY experiments on the [(CA*G)5]2 duplex where the adenines are 15N-labeled at N6. Temperature- and pH-dependent imino proton spectra, nondenaturing electrophoresis, and P1 digestion data demonstrate that under a wide range of solution conditions longer (CAG)n repeats (n> or =10) exist exclusively in hairpin conformation with two single-stranded loops. Finally, an in vitro replication assay with (CAG)8,21 inserts in the M13 single-stranded DNA templates shows a replication bypass for the (CAG)21 insert but not for the (CAG)8 insert in the template. This demonstrates that for a sufficiently long insert (n=21 in this case), a hairpin is formed by the (CAG)n even in presence of its complementary strand. This observation implies that the formation of hairpin by the (CAG)n may cause slippage during replication and thus may explain the observed length polymorphism.

DNA↗

PubMed1998

Hairpin induced slippage and hyper-methylation of the fragile X DNA triplets.

The fragile X triplet repeats, (GCC)n x (GGC)n are located at the 5' untranslated region of the FMR-1 gene. Inordinate repeat expansion and hyper-methylation of the CpG islands inside the repeat lead to the suppression of the FMR-1 gene and the subsequent onset and progression of the disease. Previously, we have shown that the (GCC)n strand of the fragile X repeat readily forms hairpin structures under physiological conditions (Chen et al., Proc. Natl. Acad. Sci. USA, 92:5199-5203, 1995: Mariappan et al., Nucl. Acid Res. 24:784-792, 1996). Here, we show by an in vitro assay that formation of the (GCC)n hairpins leads to slippage during replication. The slippage structure is a three-way junction with two Watson-Crick, (GCC)n x (GGC)n, arms and a third (GCC)n hairpin arm. Formation of such slippage structures during replication may explain the observed length polymorphism of the fragile X repeat. We have also studied the substrate efficiency of these three-way junctions toward the human methyltransferase. the enzyme that methylates the CpG sites in DNA. These methylation studies show that the slippage structures induced by the (GCC)n hairpins are 10-15 times more efficient substrates than either the corresponding Watson-Crick duplexes or the (GCC)n hairpins. We demonstrate by appropriate designs that the exceptional substrate efficiency of the three-way junction slippage structures is due to two factors: (i) the presence of the (GCC)n hairpin in which CpG sites are more accessible for methylation than the CpG sites in the Watson-Crick duplex and (ii) the ability of the (GCC)n hairpin in these three-way junctions to move along the Watson-Crick arms that facilitates conversion of low-affinity Watson-Crick CpG sites into high-affinity hairpin CpG sites. Therefore, we suggest that the formation of the (GCC)n hairpins during replication can explain both length polymorphism and hyper-methylation of the fragile X repeats.

Base Sequence↗

PubMed1998

The relationship between objective life status and subjective life satisfaction with quality of life.

A locally developed quality of life inventory was used to examine the relationship between objective life status and subjective satisfaction with quality of life in 8,550 participants from Hunan, China. The inventory included 112 items in 4 dimensions-physical health, psychological health, social functional status, and living conditions. Objective life status was the principal factor affecting subjective satisfaction, but discrepancies were found in some participants, especially when objective status was at the extremes of the distribution. Young, urban, or more educated participants with higher scores on objective status often had lower subjective satisfaction scores in spite of comparatively high objective status scores. Participants who ranked lower on objective status (old, rural, or less educated people) sometimes ranked higher in subjective satisfaction. Scores for subjective satisfaction always showed a normal distribution, whatever the objective satisfaction of the population. Divergence between individual objective status and subjective satisfaction was associated with hierarchy of life needs and the reference standards used for the comparison.

Adult↗

PubMed1998

From amplification to gene in thyroid cancer: a high-resolution mapped bacterial-artificial-chromosome resource for cancer chromosome aberrations guides gene discovery after comparative genome hybridization.

Chromosome rearrangements associated with neoplasms provide a rich resource for definition of the pathways of tumorigenesis. The power of comparative genome hybridization (CGH) to identify novel genes depends on the existence of suitable markers, which are lacking throughout most of the genome. We now report a general approach that translates CGH data into higher-resolution genomic-clone data that are then used to define the genes located in aneuploid regions. We used CGH to study 33 thyroid-tumor DNAs and two tumor-cell-line DNAs. The results revealed amplifications of chromosome band 2p21, with less-intense amplification on 2p13, 19q13.1, and 1p36 and with least-intense amplification on 1p34, 1q42, 5q31, 5q33-34, 9q32-34, and 14q32. To define the 2p21 region amplified, a dense array of 373 FISH-mapped chromosome 2 bacterial artificial chromosomes (BACs) was constructed, and 87 of these were hybridized to a tumor-cell line. Four BACs carried genomic DNA that was amplified in these cells. The maximum amplified region was narrowed to 3-6 Mb by multicolor FISH with the flanking BACs, and the minimum amplicon size was defined by a contig of 420 kb. Sequence analysis of the amplified BAC 1D9 revealed a fragment of the gene, encoding protein kinase C epsilon (PKCepsilon), that was then shown to be amplified and rearranged in tumor cells. In summary, CGH combined with a dense mapped resource of BACs and large-scale sequencing has led directly to the definition of PKCepsilon as a previously unmapped candidate gene involved in thyroid tumorigenesis.

Adenocarcinoma, Follicular↗

PubMed1998

Studies of iron deposits, inducible nitric oxide synthase and nitrotyrosine in a rat model for esophageal adenocarcinoma.

A rat model was developed recently in our laboratory to study the pathogenesis of Barrett's esophagus (BE) and its progression to esophageal adenocarcinoma (EAC). Eight-week-old male Sprague-Dawley rats underwent esophagoduodenal anastomosis (EDA) to produce gastric and duodenal reflux in their distal esophagi. The rats were given iron dextran (50 mg of Fe/kg, i.p.) starting 2 weeks after surgery and this was continued once a month. BE was observed as early as week 3 and the incidence of BE and EAC increased with time: 58 and 17% at week 23; 91 and 73% at week 31. There was a progression in epithelial cell proliferation and inflammation from mild to severe in the distal one-third of the esophagus. Iron deposition in the esophagus also increased with time. Iron deposits in the stromal tissue adjacent to the epithelium in the distal one-third of the esophagus were associated with areas of severe inflammation. Immunohistochemical analysis showed positive inducible nitric oxide synthase (iNOS) expression in the stromal macrophages directly beneath the epithelium in the distal one-third of the esophagus in 36, 83 and 100% of the rats at weeks 17, 23 and 31, respectively. A significant increasing linear trend (P=0.001) was seen in nitrotyrosine immunostaining (number of positive cells/high power field) in the distal esophagus. Strong positive nitrotyrosine staining was seen in the macrophages and weaker positive staining was seen in the adjacent epithelium starting at week 17. Furthermore, iron supplemented rats killed at week 31 had significantly higher (P < 0.05) levels of inflammation, cell proliferation, iNOS and nitrotyrosine as well as more tumors in their distal esophagi than did rats that received no iron supplement. These results suggest that iron supplementation enhanced inflammation and the production of reactive oxygen and nitrogen species in the esophageal epithelium. These processes could contribute to the formation of BE and its progression to EAC.

Adenocarcinoma↗

PubMed1998

A genetic screen for modifiers of UFO meristem activity identifies three novel FUSED FLORAL ORGANS genes required for early flower development in Arabidopsis.

In a screen to identify novel genes required for early Arabidopsis flower development, we isolated four independent mutations that enhance the Ufo phenotype toward the production of filamentous structures in place of flowers. The mutants fall into three complementation groups, which we have termed FUSED FLORAL ORGANS (FFO) loci. ffo mutants have specific defects in floral organ separation and/or positioning; thus, the FFO genes identify components of a boundary formation mechanism(s) acting between developing floral organ primordia. FFO1 and FFO3 have specific functions in cauline leaf/stem separation and in first- and third-whorl floral organ separation, with FFO3 likely acting to establish and FFO1 to maintain floral organ boundaries. FFO2 acts at early floral stages to regulate floral organ number and positioning and to control organ separation within and between whorls. Plants doubly mutant for two ffo alleles display additive phenotypes, indicating that the FFO genes may act in separate pathways. Plants doubly mutant for an ffo gene and for ufo, lfy, or clv3 reveal that the FFO genes play roles related to those of UFO and LFY in floral meristem initiation and that FFO2 and FFO3 may act to control cell proliferation late in inflorescence development.

Alleles↗

PubMed1998

Effects of dietary vitamin E supplementation on lipid oxidation and volatiles content of irradiated, cooked turkey meat patties with different packaging.

A study was conducted to determine the effects of dietary vitamin E supplementation on the storage stability and volatiles production in irradiated cooked turkey meat. Turkeys, raised with diets containing 25, 50, 75, or 100 IU of dl-alpha-tocopheryl acetate (TA)/kg diet from 1 to 105 d of age, were fed with diets containing 25, 200, 400, or 600 IU of TA/kg diet from 105 to 122 d of age. Breast and leg meat patties were prepared, irradiated at 0 or 2.5 kGy dose, cooked to an internal temperature of 78 C, and stored in either vacuum or aerobic packaging. Thiobarbituric acid reactive substance (TBARS) values gradually decreased as the dietary TA increased and > 200 IU TA/kg diet treatments were helpful in maintaining low TBARS values in irradiated breast and leg meat patties during the 7-d storage period. With vacuum-packaging, irradiated cooked breast patties developed more oxidation than nonirradiated patties but the prooxidant effect of irradiation in cooked leg meat patties was not consistent. In aerobic-packaged cooked meat, irradiated patties had lower TBARS than nonirradiated patties in both breast and leg meat stored in oxygen permeable bags for 7 d. Propanal, pentanal, hexanal, 1-pentanol, and total volatiles were highly correlated with the TBARS values of meat. However, hexanal represented the lipid oxidation status of cooked meat better than any other volatiles component. The amount of hexanal and total volatiles in cooked breast and leg meat shows decreasing trends as dietary TA increased. In vacuum packaging, irradiated breast and leg meat had higher hexanal and total volatiles content than nonirradiated meat at both 0 and 7 d of storage. In aerobic packaging, the amount of hexanal and total volatiles greatly increased in both irradiated and nonirradiated meat patties during the 7-d storage periods. The results illustrated that the antioxidant effect of TA was not strong enough to control lipid oxidation and off-odor generation in cooked meat stored under aerobic conditions because the progress of lipid oxidation in cooked meat under aerobic condition is very rapid. However, the combination of dietary TA and vacuum packaging of cooked meat immediately after cooking could be a good strategy to minimize oxidation and volatiles production in cooked meat.

Animal Feed↗

PubMed1998

Tetramethylpyrazine, a Chinese drug, blocks coronary vasoconstriction by endothelin-1 and decreases plasma endothelin-1 levels in experimental animals.

The purpose of this study was to investigate effects of tetramethylpyrazine (TMP), a Chinese plant-derived medicine, on coronary vasoconstriction and related electrocardiographic and histologic changes caused by endothelin-1 (ET-1), and on plasma ET-1 levels. ET-1 (75 pmol) was administered into the left coronary artery (LCA) in anesthetized closed-chest dogs with and without prior infusion of TMP (80 mg/kg). Coronary arterial diameter (CAD) was determined by coronary arteriography (CAG). Blood pressure and electrocardiogram (ECG) were monitored continuously. Histologic damage in tissues was ascertained microscopically. Plasma ET-1 and 6-keto-PGF1 levels were determined by RIA 90 min after i.v. injection of TMP (25 mg/kg; n = 5) in rabbits. Intracoronary injection of ET-1 resulted in a significant vasoconstriction of the entire vascular bed of the LCA, with a decrease in CAD of 35.9 +/- 5.7% (n = 5; p < 0.01) and ischemic changes on ECG and in tissues of endocardium, myocardium, coronary endothelial cells, and capillary vessels. Pretreatment with TMP produced a significant increase in CAD by 38.5 +/- 7.8% (n = 5; p < 0.01) and greatly suppressed the vasoconstriction produced by ET-1. The myocardial tissue damage estimated from the ratio of ischemic area for the entire area after ET-1 injection (35.6%) was completely abolished by TMP (0.6%). In addition, TMP injection induced a significant decrease in plasma ET-1 levels and an increase in 6-keto-PGF1 levels in rabbits. The Chinese medicine TMP could be a useful therapeutic agent in ischemic heart disease by suppressing coronary vasoconstriction and ischemic changes in the tissues produced by ET-1.

6-Ketoprostaglandin F1 alpha↗

PubMed1998

Construction of an approximately 700-kb transcript map around the familial Mediterranean fever locus on human chromosome 16p13.3.

We used a combination of cDNA selection, exon amplification, and computational prediction from genomic sequence to isolate transcribed sequences from genomic DNA surrounding the familial Mediterranean fever (FMF) locus. Eighty-seven kb of genomic DNA around D16S3370, a marker showing a high degree of linkage disequilibrium with FMF, was sequenced to completion, and the sequence annotated. A transcript map reflecting the minimal number of genes encoded within the approximately 700 kb of genomic DNA surrounding the FMF locus was assembled. This map consists of 27 genes with discreet messages detectable on Northerns, in addition to three olfactory-receptor genes, a cluster of 18 tRNA genes, and two putative transcriptional units that have typical intron-exon splice junctions yet do not detect messages on Northerns. Four of the transcripts are identical to genes described previously, seven have been independently identified by the French FMF Consortium, and the others are novel. Six related zinc-finger genes, a cluster of tRNAs, and three olfactory receptors account for the majority of transcribed sequences isolated from a 315-kb FMF central region (between D16S468/D16S3070 and cosmid 377A12). Interspersed among them are several genes that may be important in inflammation. This transcript map not only has permitted the identification of the FMF gene (MEFV), but also has provided us an opportunity to probe the structural and functional features of this region of chromosome 16.

Amino Acid Sequence↗

PubMed1998

A homogeneous, ligase-mediated DNA diagnostic test.

Single-nucleotide variations are the most widely distributed genetic markers in the human genome. A subset of these variations, the substitution mutations, are responsible for most genetic disorders. As single nucleotide polymorphism (SNP) markers are being developed for molecular diagnosis of genetic disorders and large-scale population studies for genetic analysis of complex traits, a simple, sensitive, and specific test for single nucleotide changes is highly desirable. In this report we describe the development of a homogeneous DNA detection method that requires no further manipulations after the initial reaction is set up. This assay, named dye-labeled oligonucleotide ligation (DOL), combines the PCR and the oligonucleotide ligation reaction in a two-stage thermal cycling sequence with fluorescence resonance energy transfer (FRET) detection monitored in real time. Because FRET occurs only when the donor and acceptor dyes are in close proximity, one can infer the genotype or mutational status of a DNA sample by monitoring the specific ligation of dye-labeled oligonucleotide probes. We have successfully applied the DOL assay to genotype 10 SNPs or mutations. By designing the PCR primers and ligation probes in a consistent manner, multiple assays can be done under the same thermal cycling conditions. The standardized design and execution of the DOL assay means that it can be automated for high-throughput genotyping in large-scale population studies.

DNA Ligases↗

PubMed1998

A mathematical model for the assessment of hemodynamic parameters using quantitative contrast echocardiography.

A mathematical model for the assessment of hemodynamic parameters using quantitative echocardiography is presented. The method involves the intravenous injection of an ultrasonic echo contrast agent. The relative enhancement of the backscattered ultrasound intensity is measured as a function of time (the time-intensity curve). From this measurement, the volume flow rate (cardiac output) and the mixing volume are calculated. Relevant acoustic properties of the ultrasound contrast agent are discussed. An in vitro experiment is performed to corroborate the theory presented.

Calibration↗

PubMed1998

Complement activation in discordant hepatic xenotransplantation.

Little is known about hyperacute rejection in hepatic xenotransplantation. Information from clinical xenoperfusions suggests that the liver may be rejected by a mechanism less vigorous than either kidney or heart xenografts. We used the in vitro model of porcine hepatic sinusoidal endothelial cells (PHEC) incubated with either complement replete or deficient human serum to determine the relative roles of the classical and alternate pathways of complement in the immediate response to hepatic xenotransplantation. Our results suggest that either the classical or alternate pathways are capable of independently activating the complement cascade upon exposure to the porcine hepatic sinusoidal endothelium. Our results also imply that either pathway alone is capable of initiating similar degrees of injury as the entire cascade.

Acute Disease↗

PubMed1998

Bradykinin mediates myocardial ischaemic preconditioning against free radical injury in guinea-pig isolated heart.

1. Myocardial ischaemic preconditioning (IP) against free radical injury and its possible mediator(s) was investigated in a Langendorff-perfused guinea-pig heart. 2. 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) was used for triggering free radical injury in cardiac tissue. It reduced left ventricular developed pressure (LVDP), +/- dp/dtmax, heart rate (HR) and coronary flow (CF) and increased thiobarbituric acid-reactive substances (TBARS) in cardiac tissue. 3. Ischaemic preconditioning (5 min global ischaemia and 5 min reperfusion) exerted cardioprotection against DPPH-induced functional impairment, with significant improvement in LVDP, +/- dp/dtmax, HR and CF. The formation of TBARS in cardiac tissue was reduced. Blockade of bradykinin (BK) B2 receptors with icatibant (HOE 140) abolished the cardio-protective effects of IP. 4. Bradykinin (10(-7) mol/L) perfusion for 10 min protected the heart against free radical injury. The cardioprotection induced by BK was reversed by HOE 140. 5. Pretreatment with IP and BK results in cardiac protection against free radical injury through the activation of B2 receptors. Endogenously generated BK may mediate IP in the guinea-pig heart.

Adrenergic beta-Antagonists↗

PubMed1998

Implantation of active can implantable defibrillators in the right pectoral region.

Routinely the active can ICD is placed in the left side pectoral position, which theoretically gives optimal conditions for a low defibrillation threshold. Some patients, however, demand a right pectoral position, which possibly could result in a higher defibrillation threshold. A right pectoral position was used in 3 of 85 active can ICDs implanted in our institution from 1994. The DFT was 12 J in two and 18 J in one patient. Thus, right pectoral implantation is feasible and offers an alternative approach in selected patients.

Adult↗

PubMed1998

Lesion size in relation to ablation site during radiofrequency ablation.

This study was designed to investigate the effect of the convective cooling of the tip of the ablation electrode during temperature controlled radiofrequency ablation. In vivo two different application sites in the left ventricle of anaesthetised pigs were ablated and in vitro ablation was performed during two different flow-velocities in a tissue bath, while electrode contact pressure and position were unchanged. Target temperature was 80 degrees C. Obtained tip temperature, power consumption and lesion dimensions were measured. In vivo lesion volume, depth and width were found significantly larger for septal applications than apical applications (p < 0.01) and more power was used (p < 0.001). Obtained tip temperature was significantly lower in the septal applications (p < 0.001). In vitro increased convective cooling by induction of flow yielded larger lesion volume, depth and width (p < 0.01), and had higher power consumptions (p < 0.01). Obtained tip temperature did not differ significantly. For the given chosen target temperature power consumption was positively related to lesion volume (r = 0.66 in vivo and 0.65 in vitro), whereas obtained tip temperature was not (r = -0.49 in vivo and -0.61 in vitro). We conclude that during temperature controlled radiofrequency ablation lesion size differs for septal and apical left ventricular applications. Differences in convective cooling might play an important role in this respect. This is supported by our in vitro experiments, where increased convective cooling by induction of a flow around the electrode tip increases lesion dimensions and power consumptions. Furthermore we conclude that for the given target temperature the power consumption is positively correlated with lesion volume (p < 0.001), whereas the obtained tip temperature is not.

Animals↗

PubMed1998

Temperature-controlled irrigated tip radiofrequency catheter ablation: comparison of in vivo and in vitro lesion dimensions for standard catheter and irrigated tip catheter with minimal infusion rate.

INTRODUCTION: In patients with ventricular tachycardias due to structural heart disease, catheter ablation cures < 60% partly due to the limited lesion size after conventional radiofrequency ablation. Irrigated tip radiofrequency ablation using power control and high infusion rates enlarges lesion size, but has increased risk of cratering. The present study explores irrigated tip catheter ablation in temperature-controlled mode, target temperature 60 degrees C, using an irrigation rate of 1 mL/min, comparing this to conventional catheter technique, target temperature 80 degrees C. METHODS AND RESULTS: In vivo anesthetized pigs were ablated in the left ventricle. In vitro strips of porcine left ventricular myocardium were ablated in a tissue bath. Lesion volume was significantly larger after irrigated tip ablation both in vivo (544 +/- 218 vs 325 +/- 194 mm3, P < 0.01) and in vitro (286 +/- 113 vs 179 +/- 23 mm3, P < 0.001). The incidence of cratering was not significantly different between the two groups. In vivo, no coagulum formation on part of the catheter tip was seen after irrigated tip ablation as opposed to 52% of the applications with conventional ablation (P < 0.05). CONCLUSION: We conclude that temperature-controlled radiofrequency ablation with irrigated tip catheters using low target temperature and low infusion rate enlarges lesion size without increasing the incidence of cratering and reduces coagulum formation of the tip.

Animals↗