PMA-activated neutrophils decrease ectoenzyme activities in rabbit aortic endothelial cells in culture

We have studied the effects of phorbol 12-myristate 13-acetate (PMA)-activated neutrophils [polymorphonuclear leukocytes (PMN)] on endothelial ectoenzyme [angiotensin-converting enzyme (ACE) and 5'-nucleotidase (NCT)] activities in cultured rabbit aortic endothelial cells (EC) with the use of [3H]benzoyl-Phe-Ala-Pro and 14C-labeled AMP as substrates, respectively, under first-order reaction conditions. PMA (1-1,000 ng/ml) or PMN alone had no effect on ACE activity. When PMA was incubated together with PMN (PMN/EC = 1.25:1 or 2.5 x 10(5) neutrophils/ml) for 4 h in Earle's salts, a PMA dose-dependent decrease in ACE activity was observed. Threshold PMA concentration was 2 ng/ml. At 8 ng PMA/ml, ACE activity was totally abolished, without any evidence of cytotoxicity, as inferred from release of 51Cr from prelabeled EC. The decrease in ACE activity was also dependent on PMN concentration and was detectable at PMN/EC values as low as 1.25:10 (0.25 x 10(5) PMN/ml). Inhibition of ACE occurred as early as 1 h after incubation (PMA 10 ng/ml, PMN/EC = 1.25:1). PMA alone caused a small but significant increase in NCT activity, whereas PMA coincubation with PMN produced a significant decrease in NCT activity (20-29%), which was PMA and PMN concentration independent. PMA increased PMN adherence to endothelial monolayers in a concentration-dependent manner. Pretreating PMN with monoclonal antibody 60.3 (raised against the adhesion glycoprotein CD18) or placing a 2-microns filter between PMN and EC, protected the decrease in ACE activity.(ABSTRACT TRUNCATED AT 250 WORDS)

[The experimental studies of the effect of Forskolin on the lowering of intraocular pressure]

The effect of the domestic Forskolin on lowering the intraocular pressure (IOP) of rabbits was studied. The results showed that the Forskolin significantly lowered the normal IOP of rabbits and blocked the ocular hypertension induced by water load in rabbits (p < 0.01). The maximum decrease value of 2%, 1% and 0.5% of the Forskolin was 0.59. 0.36 and 0.19 kPa (1 kPa = 7.5 mmHg), which showed the noticeable dose-effect relationship. Topical ocular application of Forskolin lowered IOP in 1/2 hour, reached to a peak in 2-3 hours and remained significantly for 10 hours. The pupillary diameter did not change when IOP were reduced. Furthermore, the Forskolin had potent stimulative properties to adenylate cyclase (AC). The greater the ability of the Forskolin to stimulate AC, the stronger the effect of IOP lowering.

An epidemiological survey of deformities and disabilities among 14257 leprosy patients in 11 counties

This study was planned and conducted in 11 counties in Yangzhou Prefecture, which had formerly had a high prevalence of leprosy. Out of 14257 leprosy patients, 8122 (56.97%) with permanent deformities and disabilities were found. The disability rate was much higher among patients with multibacillary (MB) leprosy (81.15%) than among those with paucibacillary (PB) leprosy (53.04%). The statistical data involving the patients and the types of deformities and disabilities are presented in this paper, and the influences of various host factors and disease factors are discussed.

A pathological study of sudden coronary death in China: report of 89 autopsy cases

This paper reports the results of a forensic pathological study of 89 autopsy cases of Sudden Coronary Death (SCD). Of 89 cases, 63 (52 male, 11 female) were narrowed by 76-100% in cross-sectional area (XSA) of the coronary artery (CA) and 26 (22 male, 4 female), by 51-75%. Atherosclerotic plaques in the CA were serious and extensive, especially in the left anterior descending and often involved several branches of CA at the same time. Recent thrombosis was found in 18 cases, haemorrhage in plaques in 17 cases. Only 2 cases had visible acute myocardial infarction. Inflammatory cell infiltration was found in coronary plaques in 36 cases. Myocardial fibrosis or small scar formation was detected in 51 cases. It is suggested that although the incidence of coronary heart disease (CHD) is low in China, SCD is the commonest mode of Sudden Unexpected Death. The majority of SCD (52%) were middle aged males (30-49 years old). Most of the cases died suddenly during sleep without any clear precipitating factors. The characteristics of occurrence and pathological changes in the CA and myocardium and the pathological diagnosis of SCD are also analysed and discussed.

Cloned DNA copies of cowpea severe mosaic virus genomic RNAs: infectious transcripts and complete nucleotide sequence of RNA 1

Cowpea severe mosaic virus (CPSMV) is a member of the comovirus group of messenger-sense RNA viruses with bipartite genomes, of which cowpea mosaic virus (CPMV) is the type member. Full-length copies of CPSMV RNA 1 were cloned in plasmids bearing a bacteriophage T7 promoter. Previously, similar clones of CPSMV RNA 2 had been obtained. A 5'-rUAUUAAAAUUUU sequence is common to RNA 1 and RNA 2. From two RNA 1 clones and four RNA 2 clones we excised non-CPSMV sequences so as to provide templates for in vitro transcripts that have only a single guanylate preceding CPSMV RNA sequences. Transcripts from the most active RNA 1 and RNA 2 clones, when mixed, showed about 5% of the infectivity of unfractionated CPSMV RNAs from virions. The longest, 1858 codon open reading frame of the 5957 nt CPSMV RNA 1 extends from an AUG at nt 257 to a UGA termination codon at nt 5831. The calculated molecular weight of the polyprotein is 208,000. Comparisons with the available amino acid residue (aa) sequence information from the complete CPMV RNA 1 sequence and the partial sequence of red clover mottle virus RNA 1 suggest that CPSMV RNA 1 specifies the expected set of five mature proteins: 32K proteinase cofactor, 58K presumed helicase, VPg 5'-linked protein of the genomic RNAs, 24K proteinase, and 87K presumed polymerase, separated by four cleavage sites. Of the determined and deduced cleavage sites of the three RNA 1 polyproteins, only that at the 24K/87K junction has a distinct aa pair in the CPSMV polyprotein. Of the five proteins, VPg and 87K show the greatest similarity between CPSMV and CPMV, with identities of 68 and 55%, respectively. Published mutational analysis of the CPMV 24K proteinase and alignment of aa sequences from three comoviruses suggest that cysteine-168, histidine-40 and glutamic acid-77 form the catalytic triad of the CPSMV 24K proteinase. Results are discussed in the context of the resistance that some cowpea (Vigna unguiculata) lines exhibit against CPMV but not against CPSMV.

PMA-activated neutrophils decrease pulmonary endothelial ectoenzyme activities in perfused rabbit lungs

We have studied the effects of phorbol 12-myristate 13-acetate (PMA, 15 micrograms) on pulmonary endothelial ectoenzyme [angiotensin-converting enzyme (ACE) and 5'-nucleotidase (NCT)] function in isolated rabbit lungs perfused in situ with platelet-poor (PPP) or platelet-rich (PRP) plasma in the presence or absence of neutrophils. Enzyme activities were estimated from the hydrolysis of the substrates [3H]benzoyl-Phe-Ala-Pro ([3H]BPAP) by ACE and 14C-labeled AMP by NCT during a single transpulmonary passage, using indicator-dilution techniques. In all treatment groups PMA produced a delayed increase in pulmonary vascular resistance to about three times the control value. PMA alone [in lungs perfused with PPP (n = 5 animals) or PRP (n = 6)] or neutrophils alone (in PPP-perfused lungs, n = 5) had no effect on enzyme activity. However, PMA-activated neutrophils (n = 5) decreased percent metabolism (%M) of [3H]BPAP from 87 +/- 3 to 77 +/- 4% (30 min after PMA), and the apparent first-order parameter [ratio of maximum activity to Michaelis constant (Amax/Km)] for ACE from 821 +/- 114 to 613 +/- 61 ml/min (30 min after PMA). At the same time, Km values of BPAP for ACE and AMP for NCT were elevated from 9.2 +/- 2.2 to 19.3 +/- 3 microM and 6.7 +/- 1.2 to 15.1 +/- 3.6 microM, respectively, whereas Amax (product of enzyme mass and rate of product formation, thus an index of perfused microvascular surface area) did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Somatostatin concentrations in cerebrospinal fluid and brain tissue of patients with refractory epilepsy

The somatostatin concentrations of cerebrospinal fluid (CSF) and brain tissue in 16 refractory epileptic patients were measured simultaneously by a radioimmunoassay (RIA) method. An increased level of somatostatin was found in the epileptic foci of cerebral cortex, determined by the cortical EEG. There were significant differences among the epileptic foci (75.58 +/- 6.58 pg/mg wet wt, +/- SEM), nonfocal tissues (37.04 +/- 6.55 pg/mg), and normal tissues of control patients (47.69 +/- 10.12 pg/mg), p < 0.001 and p < 0.05, respectively. The somatostatin concentrations of CSF in 11 epileptic patients were determined before (257.78 +/- 19.11 pg/mL) and after (178.36 +/- 8.78 pg/mL) the removal of epileptic focal area, and a dramatic decrease of the CSF somatostatin concentration after operation was detected (p < 0.01). We also found that the somatostatin level of cerebral scar induced by head injury in cases of posttraumatic epilepsy was highest (106.39 +/- 12.41 pg/mg). The results suggested that the surgical removal of the epileptic focal area in refractory epileptic patients may reduce the increased central somatostatin level, which could play an important part in the pathophysiological process of refractory epilepsy.

Mechanism of hypertriglyceridemia in human apolipoprotein (apo) CIII transgenic mice. Diminished very low density lipoprotein fractional catabolic rate associated with increased apo CIII and reduced apo E on the particles

Hypertriglyceridemia is common in the general population, but its mechanism is largely unknown. In previous work human apo CIII transgenic (HuCIIITg) mice were found to have elevated triglyceride levels. In this report, the mechanism for the hypertriglyceridemia was studied. Two different HuCIIITg mouse lines were used: a low expressor line with serum triglycerides of approximately 280 mg/dl, and a high expressor line with serum triglycerides of approximately 1,000 mg/dl. Elevated triglycerides were mainly in VLDL. VLDL particles were 1.5 times more triglyceride-rich in high expressor mice than in controls. The total amount of apo CIII (human and mouse) per VLDL particle was 2 and 2.5 times the normal amount in low and high expressors, respectively. Mouse apo E was decreased by 35 and 77% in low and high expressor mice, respectively. Under electron microscopy, VLDL particles from low and high expressor mice were found to have a larger mean diameter, 55.2 +/- 16.6 and 58.2 +/- 17.8 nm, respectively, compared with 51.0 +/- 13.4 nm from control mice. In in vivo studies, radiolabeled VLDL fractional catabolic rate (FCR) was reduced in low and high expressor mice to 2.58 and 0.77 pools/h, respectively, compared with 7.67 pools/h in controls, with no significant differences in the VLDL production rates. In an attempt to explain the reduced VLDL FCR in transgenic mice, tissue lipoprotein lipase (LPL) activity was determined in control and high expressor mice and no differences were observed. Also, VLDLs obtained from control and high expressor mice were found to be equally good substrates for purified LPL. Thus excess apo CIII in HuCIIITg mice does not cause reduced VLDL FCR by suppressing the amount of extractable LPL in tissues or making HuCIIITg VLDL a bad substrate for LPL. Tissue uptake of VLDL was studied in hepatoma cell cultures, and VLDL from transgenic mice was found to be taken up much more slowly than control VLDL (P < 0.0001), indicating that HuCIIITg VLDL is not well recognized by lipoprotein receptors. Additional in vivo studies with Triton-treated mice showed increased VLDL triglyceride, but not apo B, production in the HuCIIITg mice compared with controls. Tissue culture studies with primary hepatocytes showed a modest increase in triglyceride, but not apo B or total protein, secretion in high expressor mice compared with controls. In summary, hypertriglyceridemia in HuCIIITg mice appears to result primarily from decreased tissue uptake of triglyceride-rich particles from the circulation, which is most likely due to increased apo CIII and decreased apo E on VLDL particles. the HuCIIITg mouse appears to be a suitable animal model of primary familial hypertriglyceridemia, and these studies suggest a possible mechanism for this common lipoprotein disorder.

cAMP induces up-regulation of ETA receptor mRNA and increases responsiveness to endothelin-1 of rat aortic smooth muscle cells in primary culture

The effects of cAMP on the expression of ETA (ET-1 selective type) receptor mRNA and on the response to endothelin-1 (ET-1) were investigated in rat aortic smooth muscle cells in primary culture, using reverse transcription polymerase chain reaction (RT-PCR) and fura-2 microfluorometry of cytosolic Ca2+ concentrations ([Ca2+]i). Incubation of the smooth muscle cells with 10 microM forskolin and 10 microM 3-isobutyl-1-methyl-xanthine (IBMX) induced an increase in ETA receptor mRNA by 420% of control after 24 hours. ET-1 induced a biphasic increase in [Ca2+]i, first transient and second sustained phases. Incubation of the smooth muscle cells with forskolin and IBMX for 24 hours increased the [Ca2+]i response by 849% in the first phase and 286% in the second phase, compared with time-matched controls. From these results, we conclude that cAMP induces an up-regulation of the ETA receptor mRNA and increases responsiveness to ET-1 of rat aortic smooth muscle cells in primary culture.

Catalysis by mutants of human carbonic anhydrase II: effects of replacing hydrophobic residues 198 and 204

Previous studies shows that the replacement of Phe-198 in carbonic anhydrase III to the corresponding Leu residue found in carbonic anhydrase II caused the appearance of isozyme II-like activity (LoGrasso et al. (1991) Biochemistry 30, 8463-8470). Carbonic anhydrase II is more efficient in the catalysis of CO2 hydration by 500-fold and has an apparent pKa for this catalysis about two pKa units above that of carbonic anhydrase III. Moreover, isozyme II catalyzes the hydrolysis of 4-nitrophenyl acetate, whereas isozyme III shows no appreciable catalysis. The purpose of this work was to test the hypothesis that making the converse replacement Leu-198-->Phe as well as Leu-204-->Glu and the double replacement in carbonic anhydrase II would give the resulting mutants of isozyme II properties of isozyme III. The catalytic activities of these mutants in CO2 hydration and 4-nitrophenyl acetate hydrolysis were smaller by at most 5-fold and the pKa values for these catalyses were identical compared with wild-type isozyme II. The different effects of converse mutants of HCA II and III indicate complexity in structure not evident from their similar backbone conformations.

Tyrosine-ester sulfotransferase from rat liver: bacterial expression and identification

A nucleotide sequence that had been proposed for, but not identified as, rat liver aryl sulfotransferase (EC 2.8.2.1) was prepared in an appropriate vector and transformed into Escherichia coli. The protein, expressed in large amounts, was not aryl sulfotransferase (EC 2.8.2.1) but rather tyrosine-ester sulfotransferase (EC 2.8.2.9), a sulfotransferase also active with phenols but having a much wider substrate range that includes hydroxylamines and esters of tyrosine. The recombinant tyrosine-ester sulfotransferase was identified by its unique substrate spectrum, by comparison with three peptides that were sequenced from homogeneous tyrosine-ester sulfotransferase isolated directly from rat liver, and by the specificity of antibody raised to the rat liver enzyme. Two isoforms were obtained, each of which was difficult to solubilize upon sonication of E. coli. Both forms were solubilized with a solution of polyols (glycerol and sucrose) and subsequently purified to homogeneity.

[Regulation of purine biosynthesis. I. Isolation of add:: MudJ (lacZ, Kanr) insertions and genetic mapping]

Report here is the isolation of adenosine deaminase deficient mutants and genetic mapping. Engineering transposon MudJ (lacZ, Kanr) was used for mutagenesis and six add:: MudJ were obtained among 20,000 Kanr transductants. Adenosine deaminase activity of these mutants were assayed and all are negative. Cotransduction analysis of add::MudJ indicated that add is 70% linked to pmi(31') and 37% linked to zxx1900::Tn10d-tet insertion which is 10% linked to purR(30'). Three points cross showed that add is located between pmi and Tn10d-tet insertion. Therefore the gene order is purR-zxx1900::Tn10d-tet-add-pmi.

Differences in FM response correlate with morphology of neurons in the rat inferior colliculus

The response characteristics to linear frequency sweeps were studied in two groups of FM (frequency modulation) sensitive neurons in the rat inferior colliculus. 'FM specialized' cells responded to frequency sweeps but not to pure tones. 'Mixed' cells responded to both frequency sweeps and pure tones. FM specialized cells preferred faster and broader sweeps of higher intensity than did mixed cells and were more directionally selective. In addition, FM specialized cells were more sharply tuned to FM velocity and FM range and had longer response latencies. Physiologically identified FM cells stained intracellularly with horseradish peroxidase revealed differences in morphology correlating with the differences in their responses to tones. FM specialized cells had larger dendritic fields, more dendritic branching and more dendritic spines than did mixed cells. The findings are taken as evidence that the two groups of inferior colliculus neurons are both functionally and morphologically distinct.

[Initial presentation of ventricular pre-excitation after catheter ablation of concealed retrograde conducting accessory atrioventricular pathways]

Catheter ablation using radiofrequency or direct current energy was performed in 19 consecutive patients with concealed accessory pathways. Four patients developed manifest preexcitation for the first time following ablation. The concealed accessory pathways of these four patients were localized at right lateral, left posteroseptal, left posterolateral, and left lateral sites, respectively. In two patients, manifest preexcitation developed immediately after attempted ablation. In the other two patients, preexcitation occurred after 4 and 14 days. Electrophysiologic testing revealed in all four patients that the origin of manifest preexcitation corresponded to the site of the concealed pathway. Successful catheter ablation using radiofrequency current was performed in three patients. One patient preferred surgical interruption of the accessory pathway. The reason for this sudden emergence of preexcitation of these patients with only retrograde conducting pathways remains to be investigated. The anterograde conduction capacity might have been modified by damaging the site of the accessory pathway insertion.

A CD44-like endothelial cell transmembrane glycoprotein (GP116) interacts with extracellular matrix and ankyrin

We used complementary biochemical and immunological techniques to establish that an endothelial cell transmembrane glycoprotein, GP116, is a CD44-like molecule and binds directly both to extracellular matrix components (e.g., hyaluronic acid) and to ankyrin. The specific characteristics of GP116 are as follows: (i) GP116 can be surface labeled with Na 125I and contains a wheat germ agglutinin-binding site(s), indicating that it has an extracellular domain; (ii) GP116 displays immunological cross-reactivity with a panel of CD44 antibodies, shares some peptide similarity with CD44, and has a similar 52-kDa precursor molecule, indicating that it is a CD44-like molecule; (iii) GP116 displays specific hyaluronic acid-binding properties, indicating that it is a hyaluronic acid receptor; (iv) GP116 can be phosphorylated by endogenous protein kinase C activated by 12-O-tetradecanoylphorbol-13-acetate and by exogenously added protein kinase C; and (v) GP116 and a 20-kDa tryptic polypeptide fragment of GP116 from the intracellular domain are capable of binding the membrane-cytoskeleton linker molecule, ankyrin. Furthermore, phosphorylation of GP116 by protein kinase C significantly enhances GP116 binding to ankyrin. Together, these findings strongly suggest that phosphorylation of the transmembrane glycoprotein GP116 (a CD44-like molecule) by protein kinase C is required for effective GP116-ankyrin interaction during endothelial cell adhesion events.

[Percutaneous high frequency current catheter ablation in permanent ventricular tachycardia of the "bundle-branch reentry" type after implantation of an automatic cardioverter-defibrillator]

A 65-year-old female patient with a history of recurrent sustained ventricular tachycardia presented with an incessant ventricular tachycardia (cycle length 360-400 ms) following implantation of a cardioverter-defibrillator (ICD). The tachycardia could not be terminated by antiarrhythmic drug treatment, antitachycardia pacing or internal defibrillation via the ICD. An invasive electrophysiologic study revealed that the mechanism of this newly occurring tachycardia was bundle branch reentry. The patient underwent emergency catheter ablation using radiofrequency (RF) current. Endocardial mapping of the right bundle branch and of the distal His bundle was performed and a bundle branch reentry tachycardia was diagnosed. After delivery of the fifth RF-impulse, the tachycardia terminated and complete AV block was induced. No malfunction of the ICD was observed following RF-ablation. The patient was hemodynamically stable with a junctional escape rhythm and antibradycardia pacing back-up of the ICD (VVI-mode). This case report demonstrates the feasibility of RF catheter ablation in the treatment of incessant bundle branch reentry tachycardia as a complementary option after implantation of an ICD.

Tests of adipsia and conditioned taste aversion following the intrahypothalamic injection of amylin

Intrahypothalamic injection of amylin (AMY) was shown to reduce the intake of rat chow and water for 8 and 4 h, respectively, in schedule-fed rats. Amylin also reduced water intake to a much lesser degree in 24-h water-deprived rats. A test of the ability of AMY to form a conditioned taste aversion yielded no change in saccharin preference, as compared to controls treated with vehicle. These results suggest that although AMY has adipsic effects, the reduction in water is not of sufficient magnitude to cause the anorexia. In addition, the failure of AMY to support a conditioned taste aversion suggests that AMY does not cause anorexia by inducing malaise. Therefore, in addition to other metabolic effects, AMY may be involved in the control of food and water intake.

The binding of transcription factor Sp1 to multiple sites is required for maximal expression from the rat transforming growth factor alpha promoter

Transcription from the rat transforming growth factor alpha (TGF-alpha) promoter initiates at multiple sites within a 200-bp G+C-rich region that lacks TATA and CAAT motifs but contains multiple potential binding sites for the transcription factor Sp1. In the present study, we used deletion analysis to establish the 5' boundary of sequences required for efficient transcription from the predominant -58 start site. We then examined the functional activity of several putative Sp1 binding sites that occur within the transcriptionally important region downstream from -155. In the presence of either crude HeLa cell extract or purified Sp1 protein, two double-stranded oligonucleotides from this region, each of which contains three Sp1 elements, both displayed gel mobility shifts that were specifically inhibited in the presence of excess bona fide Sp1-binding sequence from the hamster dihydrofolate reductase (DHFR) gene. Methylation interference analysis of the major gel-shift complex produced with one of these oligonucleotides revealed a series of critical guanine residues located in, or adjacent to, one of the putative Sp1 recognition elements. The functional importance of Sp1 binding was confirmed by the findings that transcription in vitro from the -58 start site was inhibited in the presence of excess consensus Sp1-binding sequence and that coexpression of Sp1 dramatically induced TGF-alpha promoter-directed chloramphenicol acetyl transferase (CAT) expression in transfected Drosophila Schneider cells that otherwise lack functional Sp1. Additionally, the introduction of mutations into any of several putative Sp1 elements inhibited transcription in vitro from the -58 site, with the most proximal element tested having the largest effect. Sequential mutation of more distal elements produced a synergistic inhibition of transcription, suggesting that cooperative interactions between Sp1 sites are necessary for full expression from the TGF-alpha promoter.

[Hepatic carcinoma treated by hepatic arterial embolization using 131I and chemotherapeutic agent gelatin microspheres: report of 9 cases]

Nine patients with inoperable hepatoma were treated by using hepatic arterial embolization 131I and chemotherapeutic agent gelatin microsphere (131I-CA-GM). The emission CT after operation detected that the microspheres were concentrated on tumor area. The ratio between the radioactivity in tumor and that in liver was 4.1:1. A case died of ictopic embolization; the others survived 3, 4, 5, 19, 24, 7, 8, and 12 months respectively. Three of them were still alive. 131I-CA-GM has triple anticarcinogenic actions, including the arterial occlusion, targeting chemotherapy and internal radiation. The microspheres can selectively accumulate in the tumor artery and can be easily traced by gamma-camera or emission CT. 131I-CA-GM is a hopeful embolic agent for the treatment of liver cancer, but some problems about ectopic arterial embolization should be further studied.

Characteristics of local electrogram predicting successful transcatheter radiofrequency ablation of left-sided accessory pathways

OBJECTIVES

The purpose of this study was to analyze and compare the local electrograms recorded at successful and unsuccessful sites of ablation to identify the criteria that may predict successful sites and minimize unnecessary radiofrequency delivery.

BACKGROUND

Transcatheter ablation of accessory pathways using radiofrequency energy requires extremely precise localization of an accessory pathway.

METHODS

Local electrograms from 50 consecutive patients with left-sided accessory pathways who underwent transcatheter radiofrequency ablation were analyzed. During catheter ablation, localization of accessory pathways was performed in 39 pathways during pre-excited sinus rhythm and in 14 pathways during orthodromic tachycardia. A total of 429 local electrograms at target sites obtained before delivery of radiofrequency current was analyzed. A prospective study was performed in another 20 patients using the criteria derived from the retrospective study.

RESULTS

Accessory pathway conduction block was achieved in 36 (92%) of 39 pathways in which mapping was performed during pre-excited sinus rhythm and in 9 (64%) of 14 pathways in which mapping was performed during orthodromic tachycardia (p less than 0.05). When mapping was performed during pre-excited sinus rhythm, a combination of four variables (that is, an accessory pathway potential, stability of local electrograms, atrial activation greater than 1 mV and ventricular activation preceding the onset of the delta wave) showed a 62% probability of success. In contrast, excluding these variables resulted in a 95% probability of failure (noneffective or transiently effective). The prospective study shows that the use of these criteria can significantly reduce the number of current applications. When mapping was performed during orthodromic tachycardia, recording the earliest atrial activation was the most powerful predictor of success. A stable local electrogram with a small notch on the ventricular potential, presumed to be an accessory pathway potential, may add predictive value.

CONCLUSIONS

Transcatheter radiofrequency ablation is highly effective in the treatment of patients with left-sided accessory pathways. Specific characteristics of local electrograms can be important predictors of success or failure. Mapping during pre-excited rhythm renders ablation more effective than does mapping during orthodromic tachycardia.