Biomedical subjects

S K Huang

Publications and source records attributed to S K Huang.

At least 37 records · Page 2Linked to original sources

PubMed2000

An IL13 coding region variant is associated with a high total serum IgE level and atopic dermatitis in the German multicenter atopy study (MAS-90).

BACKGROUND: Allergic diseases are one of the major causes of morbidity in the developed countries today, and the prevalence of these diseases is increasing steadily. Study of total serum gE level is important in understanding the genetics of allergic iseases because IgE levels are considered to be a crucial pathogenic component. IL-13 plays an important role in the induction of IgE synthesis and in the pathogenesis of allergic diseases. OBJECTIVE: We sought to examine potential variation at the IL13 gene and estimate its effect on elevated IgE level and atopic dermatitis (AD). METHODS: We conducted mutational analyses of the IL13 gene by using single-stranded conformation polymorphism and DNA sequencing. Case control studies for high-IgE phenotype and AD were performed by using subjects from the German MAS-90 cohort. RESULTS: A novel IL13 coding region variant at 4257 bp (G to A, fourth exon) was identified. Case control studies of a German sample from the MAS-90 cohort showed significant associations between the presence of the A allele and two atopic phenotypes: high IgE (odds ratio, 2.38; 95% confidence interval, 1.35-4.21; P =.0026) and AD (odds ratio, 1.77; 95% confidence interval, 1.06-2.96; P =.03). CONCLUSION: This IL13 coding region variant may be involved in the pathogenesis of AD and high total serum IgE level in a study population of white subjects.

Chromosomes, Human, Pair 5↗

PubMed2000

Interferon-beta induces selective enhancement of antigen-specific T cell responses.

Interferon-beta (IFN-beta) inhibits mitogen-induced T cell responses, in part through downregulation of interleukin-12 (IL-12) or upregulation of IL-10. We have reexamined these findings using ragweed (RW) stimulated or tetanus toxoid (TT)-stimulated human peripheral blood mononuclear cells (PBMC) and nontransformed, antigen-specific, human Th0, Th1, and Th2 clones. IFN-beta induced concentration-dependent inhibition of phytohemagglutinin (PHA)-stimulated PBMC proliferation and enhancement of RW-stimulated or TTstimulated PBMC proliferation. Monocyte depletion of PBMC isolates resulted in concentration-dependent inhibition of RW-driven or TT-driven proliferation by IFN-beta. This response was unaltered by the addition of either exogenous recombinant human IL-12 (rHuIL-12) or saturating concentrations of anti-IL-10. Moreover, addition of exogenous rHuIL-10 to nondepleted RW-driven or TT-driven PBMC cultures did not alter the concentration-dependent enhancement of antigen-driven proliferation induced by IFN-beta. Th0, Th1, and Th2 clones stimulated in the presence of antigen and autologous, irradiated PBMC displayed concentration-dependent inhibition of proliferation in the presence of IFN-beta that was unaltered by the addition of either exogenous rHuIL-12 or a saturating concentration of anti-IL-10. Finally, whereas IFN-beta inhibited antigen-driven generation of IL-5, IL-12, IL-13, and IFN-gamma, IFN-beta enhanced generation of both IL-4 and IL-10. Thus, IFN-beta, induces a selective, IL-10-independent and IL-12-independent upregulation of antigen-specific T cell responses, supporting the role of IFN-beta as an immunomodulatory rather than an antiproliferative/immunosuppressive cytokine.

Adjuvants, Immunologic↗

PubMed2000

Distal end of the atrioventricular nodal artery predicts the risk of atrioventricular block during slow pathway catheter ablation of atrioventricular nodal re-entrant tachycardia.

OBJECTIVE: To search for a reliable anatomical landmark within Koch's triangle to predict the risk of atrioventricular (AV) block during radiofrequency slow pathway catheter ablation of AV nodal re-entrant tachycardia (AVNRT). PATIENTS AND METHODS: To test the hypothesis that the distal end of the AV nodal artery represents the anatomical location of the AV node, and thus could be a useful landmark for predicting the risk of AV block, 128 consecutive patients with AVNRT receiving slow pathway catheter ablation were prospectively studied in two phases. In phase I (77 patients), angiographic demonstration of the AV nodal artery and its ending was performed at the end of the ablation procedure, whereas in the subsequent phase II study (51 patients), the angiography was performed immediately before catheter ablation to assess the value of identifying this new landmark in reducing the risk of AV block. Multiple electrophysiologic and anatomical parameters were analysed. The former included the atrial activation sequence between the His bundle recording site (HBE) and the coronary sinus orifice or the catheter ablation site, either during AVNRT or during sinus rhythm. The latter included the spatial distances between the distal end of the AV nodal artery and the HBE and the final catheter ablation site, and the distance between the HBE and the tricuspid border at the coronary sinus orifice floor. RESULTS: In phase I, nine of the 77 patients had complications of transient (seven patients) or permanent (two patients) complete AV block during stepwise, anatomy guided slow pathway catheter ablation. These nine patients had a wider distance between the HBE and the distal end of the AV nodal artery, and a closer approximation of the catheter ablation site to the distal end of the AV nodal artery, which independently predicted the risk of AV block. In contrast, none of the available electrophysiologic parameters were shown to be reliable. When the distance between the distal end of the AV nodal artery and the ablation target site was more than 2 mm, the complication of AV block virtually never occurred. In phase II, all 51 patients had successful elimination of the slow pathways without complication when the ablation procedure was guided by preceding angiography with identification of the distal end of the AV nodal artery. CONCLUSIONS: The distal end of the AV nodal artery shown by angiography serves as a useful landmark for the prediction of the risk of AV block during slow pathway catheter ablation of AVNRT.

Adolescent↗

PubMed2000

Successful treatment of aconitine induced life threatening ventricular tachyarrhythmia with amiodarone.

With the increasing trend of cross mixing of populations, aconitine induced poisoning and its related arrhythmias may be more frequently encountered worldwide. However, the clinical experience is often too limited to draw any conclusion on the optimal treatment for tachycardia induced by aconitine intoxication. The clinical presentation, serial electrocardiographic changes, and responses to antiarrhythmic agents are reported in a patient with aconitine induced life threatening ventricular tachyarrhythmia. Amiodarone was effective in suppressing polymorphic ventricular tachycardia, which might provide an example of successful pharmacological intervention in aconitine induced ventricular tachyarrhythmia.

Aconitine↗

PubMed2000

IL-10 kinetics in thyroiditis-prone BB/Wor rats.

UNLABELLED: Cytokines modulate the course of autoimmunity, but their role in the evolution of spontaneous disease is unclear. This study compared the cytokine kinetics of T cell cultures from thyroiditis (LT)-prone NB line BB/Wor rats with those of Wistar (Wis) rat controls following activation with the thyroid-specific antigen thyroglobulin (Tg) or Concanavalin A (Con A). DESIGN: T cell enhanced splenocytes from 60 day old Wis and NB rats were activated with 0.5 microg/ml rat thyroglobulin (Tg) or Con A in the presence of homologous irradiated splenocytes as antigen presenting cells (APC's). In addition, the effect of APC's was determined in a crisscross experiment which examined NB T cell responses to Con A in the presence of Wis APC's. ELISA and RT-PCR were used to examine IL-2, IL-4, IL-10, TNFalpha, IFNgamma, IL-I0 concentrations and mRNA expression in the supernatant and cells from parallel cultures harvested at specific intervals. Frozen thyroids from 60 day old NB, Wis and Fisher rats were examined for the presence of IL-10 by immunohistochemistry. T cell proliferation was measured by 3H thymidine uptake. RESULTS: Following activation with either Tg or Con A, IL-10 concentrations exceeded IFNgamma in NB rat cultures, but IFNgamma exceeded IL-10 in Wis cultures. Wis splenocytes significantly enhanced NB T cell proliferation and cytokine responses to Con A. Thyroids from 60 day NB rats contained IL-10, but no IFNgamma. There was no IL-10 in thyroids from Wistar or Fisher rats. CONCLUSION: Splenocyte responses in LT-prone BB/Wor rats favor IL-10 production. Future investigations will examine the source of intrathyroidal IL-10 and its role in LT.

Animals↗

PubMed2000

Interleukin-13 modulates collagen homeostasis in human skin and keloid fibroblasts.

Interleukin (IL)-13 has been implicated in the pathogenesis of various diseases characterized by fibrosis. We describe the effects of IL-13 on collagen homeostasis from normal (NF) and keloid (KF) fibroblasts and compare these effects with those of IL-4 and transforming growth factor (TGF)-beta(1). Total collagen generation was up-regulated in NF after 48 h of stimulation by IL-13; in KF, IL-13 stimulated a more rapid collagen response. The kinetics and magnitude of collagen generation induced by IL-13 were equivalent to those induced by similar concentrations of IL-4 and TGF-beta(1). Collagen type I production paralleled total collagen generation from both NF and KF; however, IL-4-induced collagen type I and total collagen production from KF was more transient than that induced by either IL-13 or TGF-beta(1). Procollagen 1alpha1 gene expression was induced in KF by stimulation with IL-13 for 24 h. Moreover, IL-13 was unique among these three cytokines in its ability to induce gene expression for procollagen 3alpha1. Finally, IL-13 inhibited IL-1beta-induced matrix metalloproteinase (MMP)-1 and MMP-3 production and enhanced tissue inhibitor of metalloproteinase (TIMP)-1 generation from NF; although similar effects were observed with IL-4, TGF-beta(1) transiently enhanced MMP-1 and MMP-3 generation without effecting TIMP-1. In KF, IL-13 and IL-4 inhibited MMP-3, whereas TGF-beta(1) enhanced MMP-3; TIMP-1 was unaffected by any of the three cytokines. These data demonstrate both the profibrotic effects of IL-13 on collagen homeostasis and the potential differential regulation of collagen homeostasis in fibroblast subtypes by IL-13.

Cells, Cultured↗

PubMed1999

RNA melanoma vaccine: induction of antitumor immunity by human glycoprotein 100 mRNA immunization.

An RNA melanoma vaccine was investigated to induce protective immunity in a mouse-melanoma model. LacZ mRNA was synthesized in vitro by pSFV3 expression vector and introduced into the spleen of mice, using HVJ-liposomes. A high level of beta-galactosidase activity was detected for 10 days in mouse spleen. The human melanoma-associated antigen gp100 mRNA was synthesized in vitro by pSFV3 vector and encapsulated in HVJ-liposomes. Immunization by direct injection of the gp100 mRNA HVJ-liposomes into mouse spleen induced both anti-gp100 Ab and CTL responses against B16 melanoma. Immunization by administration of gp100 mRNA into the spleen delayed tumor growth and significantly prolonged survival compared with control treated mice. These preclinical studies demonstrate that an RNA tumor antigen vaccine strategy has potential application for human cancer treatment and prevention.

Animals↗

PubMed1999

Strain-dependent induction of allergic sensitization caused by peanut allergen DNA immunization in mice.

To investigate the potential application of allergen gene immunization in the modulation of food allergy, C3H/HeSn (C3H) mice received i.m. injections of pAra h2 plasmid DNA encoding one of the major peanut allergens, Ara h2. Three weeks following pDNA immunization, serum Ara h2-specific IgG2a, IgG1, but not IgE, were increased significantly in a dose-dependent manner. IgG1 was 30-fold higher in multiply compared with singly immunized mice. Ara h2 or peanut protein injection of immunized mice induced anaphylactic reactions, which were more severe in multiply immunized mice. Heat-inactivated immune serum induced passive cutaneous anaphylaxis, suggesting that anaphylaxis in C3H mice was mediated by IgG1. IgG1 responses were also induced by intradermal injection of pAra h2, and by i.m. injection of pOMC, the plasmid DNA encoding the major egg allergen protein, ovomucoid. To elucidate whether the pDNA immunization-induced anaphylaxis was a strain-dependent phenomenon, AKR/J and BALB/c mice also received multiple i.m. pAra h2 immunizations. Injection of peanut protein into these strains at weeks 3 or 5 following immunization did not induce reactions. Although IgG2a was increased significantly from week 2 in AKR/J mice and from week 4 in BALB/c mice and remained elevated for at least 6 wk, no IgG1 or IgE was detected. These results indicate that the type of immune responses to pDNA immunization in mice is strain dependent. Consequently, models for studying human allergen gene immunization require careful selection of suitable strains. In addition, this suggests that similar interindividual variation is likely in humans.

Allergens↗

PubMed1999

Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group.

BACKGROUND: The purpose of this study was to evaluate the safety and efficacy of a temperature-controlled radiofrequency catheter ablation system. METHODS AND RESULTS: The patient population included 1050 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia (AVNRT), an accessory pathway (AP), or the atrioventricular junction (AVJ). Ablation was successful in 996 patients. The probability of success was highest among patients who had undergone ablation of the AVJ, lowest in patients who had undergone ablation of an AP, and in between for patients who had undergone ablation of AVNRT. A major complication occurred in 32 patients. Four variables predicted ablation success (AVJ, AVNRT, or left free wall AP ablation and an experienced center). Four factors predicted arrhythmia recurrence (right free wall, posteroseptal, septal, and multiple APs). Two variables predicted development of a complication (structural heart disease and the presence of multiple targets), and 3 variables predicted an increased risk of death (heart disease, lower ejection fraction, and AVJ ablation). CONCLUSIONS: These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

Adolescent↗

PubMed1999

Regulation of antigen-induced human T-lymphocyte responses by calcineurin antagonists.

BACKGROUND: Cyclosporin A (CS) and tacrolimus (FK506, FK) are calcineurin antagonists used widely as T-cell immunosuppressants; however, their relative efficacy on antigen-stimulated T-cell subsets remains undefined. OBJECTIVE: We have examined the effects of CS and FK on antigen-driven proliferation and cytokine generation from human PBMCs and T-cell clones. METHODS: Proliferation was assessed by tritiated thymidine incorporation. Cytokine generation was assessed by reverse transcription-PCR and ELISA. RESULTS: Ragweed- and tetanus toxoid-driven proliferation of PBMCs was down-regulated equally by CS or FK. Gene expression for proinflammatory cytokines (IL-4, IL-5, IL-13, and IFN-gamma) assessed by reverse transcription-PCR was down-regulated in a concentration-dependent manner by either drug. Antigen-induced proliferation of ragweed-specific Th0, Th1, or Th2 clones was inhibited by either CS or FK. Cytokine gene expression and protein secretion into culture supernatants (IL-4, IL-5, IL-13, and IFN-gamma) were down-regulated in a concentration-dependent manner by either CS or FK in all relevant T-cell subsets. Interestingly, down-regulation of IL-5 protein generation from Th0 and Th2 clones was consistently less sensitive to either drug than was the effect on either IL-4 or IL-13 protein generation. CONCLUSION: CS and FK promote equivalent down-regulation of Th0, Th1, and Th2 responses; however, IL-5 generation is relatively insensitive to the immunomodulatory effects of calcineurin antagonists.

Calcineurin Inhibitors↗

PubMed1999

Differential regulation of antigen-induced IL-4 and IL-13 generation from T lymphocytes by IFN-alpha.

BACKGROUND: IL-4 and IL-13 are related cytokines with similar functional properties. Differential regulation of IL-4 and IL-13 has not been described. OBJECTIVE: We have examined the effects of IFN-alpha on antigen-driven proliferation, IL-4 generation, and IL-13 generation from human PBMCs and T-cell clones. METHODS: Proliferation was assessed by 3H-thymidine incorporation. Cytokine generation was assessed by reverse transcription PCR and ELISA. Messenger RNA stability was assessed in the presence of actinomycin D. RESULTS: IFN-alpha induced a concentration-dependent inhibition of antigen-driven proliferation of TH1 and TH2 clones (median effective concentration, 150 to 200 U/mL); the sensitivity of TH1 and TH2 clones to IFN-alpha was not significantly different (P =.6). IFN-alpha induced an analogous concentration-dependent inhibition of antigen-driven IL-13 generation from TH1 and TH2 clones (median effective concentration, 100 U/mL); this effect was evident by 12 hours of culture and persisted beyond 48 hours. However, IL-4 generation from TH2 clones was insensitive to IFN-alpha at all concentrations and times tested (1 to 10,000 U/mL). A similar inhibitory effect of IFN-alpha on mitogen-driven proliferation and IL-13 generation from PBMCs was demonstrated; once again, IL-4 generation from PBMCs was insensitive to IFN-alpha. IL-13 mRNA stability was unaffected by IFN-alpha, suggesting transcriptional regulation. CONCLUSION: IFN-alpha differentially regulates antigen-stimulated IL-4 and IL-13 generation.

Adult↗

PubMed1999

Determination of Duffy genotypes in three populations of African descent using PCR and sequence-specific oligonucleotides.

The expression of the Duffy Antigen/Receptor for Chemokines (DARC) on red blood cells (RBC) has been commonly determined using hemagglutination tests. Because the vast majority of African individuals are Duffy-negative, screening for DARC expression on RBC is a valuable tool to assess Caucasian admixture in populations of African descent. Furthermore, blood group antigens have been frequently tested as potential risk factors for complex diseases. We established a dot-blotting protocol using sequence-specific oligonucleotides (SSOs) for the DARC-46T ("Duffy-positive") and -46C ("Duffy-negative") alleles. With this method, but not with serological methods, Duffy-positive individuals can be further characterized as homozygous or heterozygous for the dominant Duffy-positive allele, allowing more precise estimation of allele frequencies and admixture in heterogeneous populations. In unrelated African American (n = 235), Afro-Caribbean (n = 90) and Colombian (n = 93) subjects, the frequency of the -46T allele was 21.7%, 12.2% and 74.7%, respectively. The percentage of Duffy-positive individuals (homozygous or heterozygous for the -46T allele) in each population was in accordance with published frequencies. As expected, the -46C allele was not detected in 20 Caucasian subjects. This sensitive and specific method allows for the rapid and inexpensive screening of large samples for Duffy genotypes using small quantities of genomic DNA.

Alleles↗

PubMed1999

Down-regulation of L-type calcium channel and sarcoplasmic reticular Ca(2+)-ATPase mRNA in human atrial fibrillation without significant change in the mRNA of ryanodine receptor, calsequestrin and phospholamban: an insight into the mechanism of atrial electrical remodeling.

OBJECTIVES: We investigated the gene expression of calcium-handling genes including L-type calcium channel, sarcoplasmic reticular calcium adenosine triphosphatase (Ca(2+)-ATPase), ryanodine receptor, calsequestrin and phospholamban in human atrial fibrillation. BACKGROUND: Recent studies have demonstrated that atrial electrical remodeling in atrial fibrillation is associated with intracellular calcium overload. However, the changes of calcium-handling proteins remain unclear. METHODS: A total of 34 patients undergoing open heart surgery were included. Atrial tissue was obtained from the right atrial free wall, right atrial appendage, left atrial free wall and left atrial appendage, respectively. The messenger ribonucleic acid (mRNA) amount of the genes was measured by reverse transcription-polymerase chain reaction and normalized to the mRNA levels of glyceraldehyde 3-phosphate dehydrogenase. RESULTS: The mRNA of L-type calcium channel and of Ca(2+)-ATPase was significantly decreased in patients with persistent atrial fibrillation for more than 3 months (0.36+/-0.26 vs. 0.90+/-0.88 for L-type calcium channel; 0.69+/-0.42 vs. 1.21+/-0.68 for Ca(2+)-ATPase; both p < 0.05, all data in arbitrary unit). We further demonstrated that there was no spatial dispersion of the gene expression among the four atrial tissue sampling sites. Age, gender and underlying cardiac disease had no significant effects on the gene expression. In contrast, the mRNA levels of ryanodine receptor, calsequestrin and phospholamban showed no significant change in atrial fibrillation. CONCLUSIONS: L-type calcium channel and the sarcoplasmic reticular Ca(2+)-ATPase gene were down-regulated in atrial fibrillation. These changes may be a consequence of, as well as a contributory factor for, atrial fibrillation.

Adolescent↗

PubMed1999

Oral gene delivery with chitosan--DNA nanoparticles generates immunologic protection in a murine model of peanut allergy.

Food allergy is a common and often fatal disease with no effective treatment. We describe here a new immunoprophylactic strategy using oral allergen-gene immunization to modulate peanut antigen-induced murine anaphylactic responses. Oral administration of DNA nanoparticles synthesized by complexing plasmid DNA with chitosan, a natural biocompatible polysaccharide, resulted in transduced gene expression in the intestinal epithelium. Mice receiving nanoparticles containing a dominant peanut allergen gene (pCMVArah2) produced secretory IgA and serum IgG2a. Compared with non-immunized mice or mice treated with 'naked' DNA, mice immunized with nanoparticles showed a substantial reduction in allergen-induced anaphylaxis associated with reduced levels of IgE, plasma histamine and vascular leakage. These results demonstrate that oral allergen-gene immunization with chitosan-DNA nanoparticles is effective in modulating murine anaphylactic responses, and indicate its prophylactic utility in treating food allergy.

2S Albumins, Plant↗

PubMed1999

Usefulness of intravenous propofol anesthesia for radiofrequency catheter ablation in patients with tachyarrhythmias: infeasibility for pediatric patients with ectopic atrial tachycardia.

General anesthesia is sometimes required during radiofrequency catheter ablation (RFCA) of various tachyarrhythmias because of an anticipated prolonged procedure and the need to ensure stability during critical ablation. In this study, we examine the feasibility of using propofol anesthesia for RFCA procedure. There were 150 patients (78 male, 72 female; mean age 30 years, range 4-96 years) in the study. Electrophysiologic study was performed before and during propofol infusion in the initial 20 patients and was performed only during propofol infusion in the remaining 130 patients. In the initial 20 patients, propofol infusion increased the sinus rate and facilitated AV nodal conduction. The accessory pathway effective refractory period, as well as the sinus node recovery time, atrial effective refractory period, and ventricular effective refractory period were not significantly changed. There were 152 tachyarrhythmias in 150 patients (24 atrial flutter, 31 AV nodal reentrant tachycardia, 68 AV reciprocating tachycardia, 12 ventricular tachycardia, and 17 atrial tachycardia). Most (148/152) tachycardias remained inducible after anesthesia and RFCA was performed uneventfully. However, in four of the seven pediatric patients with ectopic atrial tachycardia, the tachycardia terminated after propofol infusion and could not be induced by isoproterenol infusion. Consequently, RFCA could not be performed. Intravenous propofol anesthesia is feasible during RFCA for most tachyarrhythmias except for ectopic atrial tachycardia in children.

Adolescent↗

PubMed1999

Electrophysiologic study and radiofrequency catheter ablation of isthmus-independent atrial flutter.

INTRODUCTION: We report the electrophysiologic study and radiofrequency catheter ablation of isthmus-independent atrial flutter in 2 patients. The isthmus-independent atrial flutter in these 2 patients had similar ECG and electrophysiologic findings. Both were reproducibly induced by rapid atrial pacing. The atrial activation sequence and entrainment study proved that these atrial flutters were not isthmus-dependent. A high-right atrial site was identified as the critical site of the slow conduction zone of the tachycardia in both. This site showed double potentials and mid-diastolic potentials. Radiofrequency catheter ablation at this site successfully eliminated the isthmus-independent atrial flutter in both patients.

Atrial Flutter↗

PubMed1999

Measurement of funny current (I(f)) channel mRNA in human atrial tissue: correlation with left atrial filling pressure and atrial fibrillation.

INTRODUCTION: The funny current (I(f)) contributes to phase IV spontaneous depolarization in cardiac pacemaker tissue. Enhanced I(f) activity in myocardial tissue may lead to increased automaticity and therefore tachyarrhythmia. We measured the amount of I(f) activity in the messenger ribonucleic acid (mRNA) in human atrial tissue and correlated the mRNA amount to left atrial filling pressure and atrial fibrillation (AF). METHODS AND RESULTS: A total of 34 patients undergoing open heart surgery were included (15 men and 19 women, aged 55+/-10 years). Atrial tissue was obtained from the right atrial free wall, the right atrial appendage, the left atrial free wall, and the left atrial appendage, respectively. The mRNA amount of the I(f) channel was measured by reverse transcription polymerase chain reaction and was normalized to the mRNA levels of glyceraldehyde 3-phosphate dehydrogenase. We found that the I(f) channel mRNA was present at all the atrial sampling sites. A higher left atrial filling pressure, an indicator of congestive heart failure, was associated with a higher I(f) mRNA level (r2 = 0.446, P < 0.01 by linear regression). We also found that the mRNA amount was significantly higher in patients with AF than in patients without AF (1.68+/-0.49 vs 1.27+/-0.43; P < 0.05). Age, sex, right atrial filling pressure, left atrial dimension, and left ventricular ejection fraction had no significant effect on the mRNA level. CONCLUSION: The mRNA of the I(f) channel is present in the free-wall area and appendage area from both atria. Increased left atrial filling pressure and clinical AF are associated with increased I(f) mRNA level.

Adolescent↗

PubMed1999

Electrophysiological determinant for induction of isthmus dependent counterclockwise and clockwise atrial flutter in humans.

OBJECTIVE: To investigate the electrophysiological determinant underlying the electrical induction of counterclockwise and clockwise isthmus dependent atrial flutter. PATIENTS AND METHODS: The isthmus bordered by the inferior vena caval orifice-tricuspid annulus-coronary sinus ostium (IVCO-TA-CSO) has been assumed to be the site of both slow conduction and unidirectional block critical to the initiation of atrial flutter. Trans-isthmus and the global atrial conduction were studied in 25 patients with isthmus dependent atrial flutter (group A) and in 21 patients without atrial flutter (group B), by pacing at the coronary sinus ostium and the low lateral right atrium (LLRA) and mapping with a 20 pole Halo catheter in the right atrium. RESULTS: Mean (SD) fluoroscopic isthmus length between the coronary sinus ostium and LLRA sites was 28.1 (4.0) mm in group A and 28.0 (3.9) mm in group B (p = 0.95), but the trans-isthmus conduction velocity of both directions at various pacing cycle lengths was nearly halved in group A compared with group B (mean 0.39-0.46 m/s v 0.83-0.89 m/s, p < 0.0001). Pacing at coronary sinus ostium directly induced counterclockwise atrial flutter in 14 patients and pacing at LLRA induced clockwise atrial flutter in 11 patients, following abrupt unidirectional trans-isthmus block. Transient atrial tachyarrhythmias preceded the onset of atrial flutter in 10 counterclockwise and six clockwise cases of atrial flutter. None of the group B patients had inducible atrial flutter even in the presence of trans-isthmus block. The intra- and interatrial conduction times, as well as the conduction velocities at the right atrial free wall and the septum, were similar and largely within the normal range in both groups. CONCLUSIONS: Critical slowing of the trans-IVCO-TA-CSO isthmus conduction, but not the unidirectional block or the global atrial performance, is the electrophysiological determinant of the induction of counterclockwise and clockwise isthmus dependent atrial flutter in man.

Adult↗