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S C Heald

Publications and source records attributed to S C Heald.

At least 19 recordsLinked to original sources
PubMed2001

Physiology, biochemistry and taxonomy of deep-sea nitrile metabolising Rhodococcus strains.

A collection of nitrile-hydrolysing rhodococci was isolated from sediments sampled from a range of deep coastal, and abyssal and hadal trench sites in the NW Pacific Ocean, as part of our programme on the diversity of marine actinomycetes. Nitrile-hydrolysing strains were obtained by batch enrichments on nitrile substrates with or without dispersion and differential centrifugation pre-treatment of sediments, and were recovered from all of the depths sampled (approximately 1100-6500 m). Two isolates obtained from the Ryukyu (5425 m) and Japan (6475 m) Trenches, and identified as strains of Rhodococcus erythropolis, were chosen for detailed study. Both of the deep-sea isolates grew at in situ temperature (4 degrees C), salinities (0-4% NaCl) and pressures (40-60 MPa), results that suggest, but do not prove, that they may be indigenous marine bacteria. However, the absence of culturable Thermoactinomyces points to little or no run off of terrestrial microbiota into these particular trench sediments. Nitrile-hydrolysis by these rhodococci was catalysed by a nitrile hydratase-amidase system. The hydratase accommodated aliphatic, aromatic and dinitrile substrates, and enabled growth to occur on a much wider range of nitriles than the only other reported marine nitrile-hydrolysing R. erythropolis which was isolated from coastal sediments. Also unlike the latter strain, the nitrile hydratases of the deep-sea rhodococci were constitutive. The possession of novel growth and enzyme activities on nitriles by these deep-sea R. erythropolis strains recommends their further development as industrial biocatalysts.

DNA, Ribosomal↗
PubMed1999

4-Chlorophenol degradation by a bacterial consortium: development of a granular activated carbon biofilm reactor.

A bacterial consortium that can degrade chloro- and nitrophenols has been isolated from the rhizosphere of Phragmitis communis. Degradation of 4-chlorophenol (4-CP) by a consortium attached to granular activated carbon (GAC) in a biofilm reactor was evaluated during both open and closed modes of operation. During the operation of the biofilm reactor, 4-CP was not detected in the column effluent, being either adsorbed to the GAC or biodegraded by the consortium. When 4-CP at 100 mg l-1 was fed to the column in open mode operation (20 mg g-1 GAC total supply), up to 27% was immediately available for biodegradation, the rest being adsorbed to the GAC. Biodegradation continued after the system was returned to closed mode operation, indicating that GAC bound 4-CP became available to the consortium. Biofilm batch cultures supplied with 10-216 mg 4-CP g-1 GAC suggested that a residual fraction of GAC-bound 4-CP was biologically unavailable. The consortium was able to metabolise 4-CP after perturbations by the addition of chromium (Cr VI) at 1-5 mg l-1 and nitrate at concentrations up to 400 mg l-1. The development of the biofilm structure was analysed by scanning electron microscopy and confocal laser scanning microscopy (CLSM) techniques. CLSM revealed a heterogeneous structure with a network of channels throughout the biofilm, partially occupied by microbial exopolymer structures.

Anaerobiosis↗
PubMed1998

Taxonomy and biotransformation activities of some deep-sea actinomycetes.

Deep-sea soft sediments from trench systems and depths in the northwestern Pacific Ocean ranging from less than 300 to 10,897 m in depth have been analyzed for three target genera of actinomycetes: Micromonospora, Rhodococcus, and Streptomyces. Only culturable strains, recovered at atmospheric pressure on selective isolation media, have been examined to date. Maximum recoveries of culturable bacteria were greater that 10(7)/ml wet g sediment, but actinomycetes comprised a small proportion of this population (usually less than 1%). The target actinomycetes were isolated at all depths except from the Mariana Trench sediments. Actinomycete colonies were defined initially on the basis of colony morphologies, and preliminary identification then was made by chemotaxonomic tests. Pyrolysis mass spectrometry (PyMS) of deep-sea mycolic acid-containing actinomycetes gave excellent correspondence with numerical (phenetic) taxonomic analyses and subsequently was adopted as a rapid procedure for assessing taxonomic diversity. PyMS analysis enabled several clusters of deep-sea rhodococci to be distinguished that are quite distinct from all type strains. 16S rRNA gene sequence analysis has revealed that several of these marine rhodococci have sequences that are very similar to certain terrestrial species of Rhodococcus and to Dietzia. There is evidence for the intrusion of terrestrial runoff into these deep trench systems, and the inconsistency of the phenotypic and molecular taxonomies may reflect recent speciatiion events in actinomycetes under the high-pressure conditions of the deep sea. The results of DNA-DNA pairing experiments point to the novelty of Rhodococcus strains recovered from hadal depths in the Izu Bonin Trench. Biotransformation studies of deep-sea bacteria have focused on nitrile compounds. Nitrile-metabolizing bacteria, closely related to rhodococci, have been isolated that grow well at low temperature, high salt concentrations, and high pressures, suggesting that they are of marine origin or have adapted to the deep-sea environment.

Actinomycetales↗
PubMed1998

Entrapment of an ablation catheter in the cardiac venous system: a case report.

Cannulation of the coronary sinus is a common procedure with infrequent complications. We report an unusual case of a steerable "dumb-bell" catheter passed through the ostium of the coronary sinus prior to an intended radiofrequency ablation procedure becoming stuck and requiring general anesthesia for extraction. We caution against the use of such catheters with a "waist" for the cannulation of the coronary sinus.

Adult↗
PubMed1997

Radiofrequency catheter ablation of accessory atrioventricular pathways: primary failure and recurrence of conduction.

OBJECTIVE: To identify possible factors associated with primary failure of radiofrequency ablation of accessory pathways or recurrence of accessory pathway conduction. PATIENTS AND METHODS: Radiofrequency ablation of accessory pathways failed in 25 of 243 patients, and recurrence of accessory pathway conduction occurred in an additional 13 patients. Factors possibly related to primary failure and recurrence were analysed. RESULTS: Primary failure and recurrence were less frequent in patients with left sided pathways (7% v 19%; 4% v 24%; P = 0.04). The factors that might relate to primary failure included an unstable catheter position (seven patients), a possible epicardial pathway (six patients), or misdiagnosis of accessory pathway location (two patients). The major factors for recurrence included the stability of the local atrial electrogram < or = 0.5 together with the stability of the local ventricular electrogram < or = 0.8, and prolonged time to pathway conduction block > or = 12 seconds). Thirty one patients underwent repeat ablation which was successful in 28. CONCLUSIONS: Primary failure and recurrence were more frequent in patients with right sided pathways. An unstable catheter position and a possible epicardial pathway location are the main contributing factors for primary failure, while unstable local electrograms and prolonged time to block are independent predictors for recurrence.

Adolescent↗
PubMed1996

Expression and substrate specificity of the toluene dioxygenase of Pseudomonas putida NCIMB 11767.

Pseudomonas putida NCIMB 11767 oxidized phenol, monochlorophenols, several dichlorophenols and a range of alkylbenzenes (C1-C6) via an inducible toluene dioxygenase enzyme system. Biphenyl and naphthalene were also oxidized by this enzyme. Growth on toluene and phenol induced the meta-ring-fission enzyme, catechol 2,3-oxygenase, whereas growth on benzoate, which did not require expression of toluene dioxygenase, induced the ortho-ring-cleavage enzyme, catechol 1,2-oxygenase. Monochlorobenzoate isomers and 2,3,5-trichlorophenol were gratuitous inducers of toluene dioxygenase, whereas 3,4-dichlorophenol was a fortuitous oxidation substrate of the enzyme. The organism also grew on 2,4- and 2,5-dichloro isomers of both phenol and benzoate, on 2,3,4-trichlorophenol and on 1-phenylheptane. During growth on toluene in nitrogen-limited chemostat culture, expression of both toluene dioxygenase and catechol 2,3-oxygenase was positively correlated with increase in specific growth rate (0.11-0.74 h-1), whereas the biomass yield coefficient decreased. At optimal dilution rates, the predicted performance of a 1-m3 bioreactor supplied with 1 g nitrogen l-1 for removal of toluene was 57 g day-1 and for removal of trichloroethylene was 3.4 g day-1. The work highlights the oxidative versatility of this bacterium with respect to substituted hydrocarbons and shows how growth rate influences the production of competent cells for potential use as bioremediation catalysts.

Biodegradation, Environmental↗
PubMed1996

Characteristics of bipolar electrograms during anterograde mapping: the importance of accessory atrioventricular pathway location.

Local endocardial electrograms recorded at successful radiofrequency ablation sites during anterograde mapping (QRS-V interval, atrioventricular [AV] interval, AV ratio, the presence of accessory pathway potential, and stability of atrial and ventricular electrogram) were analyzed and compared according to location of accessory pathways. The mitral and tricuspid annuli were divided into 10 regions. Endocardial electrograms differed with regard to location of accessory AV pathways. The QRS-V interval was more negative in right posteroseptal, right free wall and right anteroseptal locations than the interval in other locations. The AV interval was longer in posteroseptal than the interval in left and right free wall sites. The stability of atrial and ventricular electrograms was better in left free wall sites than in posteroseptal sites and worst in right free wall and right anteroseptal sites. The variation in local electrograms at successful ablation sites with respect to pathway location may partly explain the low predictive value and the marked variation in previously suggested criteria for selecting target sites for radiofrequency energy delivery. The results also imply that the influence of accessory pathway location must be considered when attempts are made to establish electrogram-based criteria for predicting successful ablation of accessory pathways.

Adolescent↗
PubMed1996

Successful radiofrequency ablation of accessory pathways with the first energy delivery: the anatomic and electrical characteristics.

Successful ablation of accessory pathways has been achieved at the first energy delivery site in some patients, but factors permitting success at the first site are unclear. Accessory pathway location, surface and endocardial electrogram characteristics in each location were analysed and compared between the patients with first site block (group A, 34 patients) and those in whom multiple sites (median seven sites) were required (group B, 133 patients). No patients with right free-wall pathways had first site block. In group A surface electrocardiograms were more pre-excited (QRS duration: 132 +/- 20 vs 120 +/- 17 ms, P < 0.01). For left free-wall and septal pathways, the interval from the onset of the earliest delta wave on surface electrocardiogram to local ventricular activation (QRS-V) was more negative and the local atrioventricular interval (AV) was shorter in group A; the positive predictive value of a QRS-V < or = 0 ms, an AV < or = 30 ms and the presence of a possible accessory pathway potential was 67% for left free-wall and of a QRS-V < or = -10 ms with an AV < or = 30 ms was 100% for septal pathways. During retrograde mapping of concealed left free-wall and right anteroseptal pathways (first site block was not achieved in other locations) the positive predictive value of a local ventriculoatrial interval < or = 30 ms was 55%. Accessory pathway location correlated strongly with the chances of first site block, suggesting that anatomical features are important. Maximizing pre-excitation may be of benefit in achieving first site block. Delivery of energy to a site with special endocardial electrogram features was associated with an increased likelihood of first site block.

Accessory Nerve↗
PubMed1995

Prediction of atrioventricular block during radiofrequency ablation of the slow pathway of the atrioventricular node.

BACKGROUND: Selective radiofrequency (RF) ablation of the slow pathway is an effective treatment for atrioventricular (AV) nodal reentry tachycardia. A previous report showed that rapid junctional tachycardia (JT) caused by RF associated with loss of ventriculoatrial (VA) conduction is related to increased risk for AV block. However, this can be difficult to detect during energy delivery, and more importantly, it cannot be measured before the onset of RF energy delivery. The aim of our study was to determine whether measurements made from electrograms could be used to predict the risk of AV block before RF energy is delivered. METHODS AND RESULTS: Fifty-eight patients underwent 63 selective slow pathway RF ablation procedures. In 46 (26.9%) of 172 JTs caused by RF, VA block was observed, and in 11 this was followed by AV block of various degrees. Electrograms before each application of RF were analyzed for the interval between the atrial signals in the His bundle catheter and in the distal mapping catheter [A(H)-A(Md)], the interval between the atrial signals in the His bundle catheter and in the proximal coronary sinus catheter [A(H)-A(CS)], the AV ratio, and the presence of a slow pathway potential or a fractionated atrial signal in the distal mapping catheter. Mean cycle length (CL) of JT was calculated if it consisted of at least 10 beats. These parameters were compared between patients with JT who developed VA block and subsequent AV block (group 1), patients with JT and VA block but without subsequent AV block (group 2), and patients with JT without VA block (group 3). The A(H)-A(Md) interval was significantly shorter in group 1 (17 +/- 8 ms) than in groups 2 (33 +/- 8 ms, P < .001) and 3 (32 +/- 10 ms, P < .001), whereas the A(H)-A(Md) intervals of groups 2 and 3 did not differ from each other. CL of JT, A(H)-A(CS) interval, AV ratio, presence of a slow pathway potential, or a fractionated atrial electrogram were not related to the occurrence of AV block. CONCLUSIONS: The A(H)-A(Md) interval provides an electrophysiological marker that can be used in addition to the radiological catheter position to assess the risk for AV block before onset of RF delivery. CL of JT and occurrence of VA block are not related to the risk of AV block.

Atrioventricular Node↗
PubMed1995

Influence of the infarct site on the identification of patients with ventricular tachycardia after myocardial infarction based on the time-domain and spectral turbulence analysis of the signal-averaged electrocardiogram.

In a significant proportion of patients with sustained ventricular tachycardia (VT) following anterior myocardial infarction, the areas of slow conduction are activated early during cardiac depolarization. Therefore, they may not be detected by the standard time-domain analysis of the signal-averaged electrocardiogram (SAECG) which is limited to the terminal part of the QRS complex. Spectral turbulence analysis of the SAECG is a new frequency domain technique which examines the whole QRS complex and may improve identification of patients with sustained VT following anterior infarction. We compared the results of time-domain and spectral turbulence analyses of the SAECG in 53 postinfarction patients with sustained VT and in 53 age-, gender- and infarct site-matched patients without VT. The receiver operator characteristic curves have shown that the time-domain analysis resulted in better identification of patients with VT following inferior than following anterior infarction (e.g., at the sensitivity level of 90%, the corresponding values of specificity were 96 and 90%, respectively), whereas the spectral turbulence analysis performed better in the anterior site of infarction. When both time-domain and spectral turbulence analyses were combined, the accuracy of the SAECG for identification of patients with VT following anterior infarction improved, reaching a specificity of 97% at the sensitivity level of 90%. In conclusion (1) spectral turbulence analysis of the SAECG results in better identification of patients with VT following anterior than following inferior infarction, and (2) the combination of time-domain and spectral turbulence analyses of the SAECG may improve identification of patients with VT following anterior infarction.

Aged↗
PubMed1995

Radiofrequency catheter ablation of Mahaim tachycardia by targeting Mahaim potentials at the tricuspid annulus.

BACKGROUND: Reentrant tachycardias associated with Mahaim pathways are rare but potentially troublesome. Various electrophysiological substrates have been postulated and catheter ablation at several sites has been described. OBJECTIVE: To assess the efficacy and feasibility of targeting discrete Mahaim potentials recorded on the tricuspid annulus for the delivery of radiofrequency energy in the treatment of Mahaim tachycardia. PATIENTS: 21 patients out of a consecutive series of 579 patients referred to one of three tertiary centres for catheter ablation of accessory pathways causing tachycardia. All had symptoms and presented with tachycardia of left bundle branch block configuration or had this induced at electrophysiological study. In all cases, the tachycardia was antidromic with anterograde conduction over a Mahaim pathway. RESULTS: 6 patients had additional tachycardia substrates (4 had accessory atrioventricular connections and 2 had dual atrioventricular nodal pathways and atrioventricular nodal reentry). After ablation of the additional pathways, Mahaim potentials were identified in 16 (76%) associated with early activation of the distal right bundle branch and radiofrequency energy at this site on the tricuspid annulus abolished Mahaim conduction in all 16 cases. In 2 patients there was early ventricular activation at the annulus without a Mahaim potential but radiofrequency energy abolished pre-excitation. In the remaining patients no potential could be found (1 patient), no tachycardia could be induced after ablation of an additional pathway (1 patient), or no Mahaim conduction was evident during the study (1 patient). During follow up (1-29 months (median 9 months)) all but 1 patient remained symptom free without medication. CONCLUSIONS: Additional accessory pathways seem to be common in patients with Mahaim tachycardias. The identification of Mahaim potentials at the tricuspid annulus confirms that most of these pathways are in the right free wall and permits their successful ablation and the abolition of associated tachycardia.

Adolescent↗
PubMed1994

Localization of accessory pathways from the 12-lead electrocardiogram using a new algorithm.

A new algorithm (St. George's algorithm), based on the polarity and morphology of QRS complexes rather than delta waves, was developed for localizing accessory pathways to 1 of 9 sites on the atrioventricular annuli. This was compared with algorithms previously proposed by Skeberis et al (localizing to 1 of 7 sites) and Milstein et al (localizing to 1 of 4 sites). The preexcited 12-lead electrocardiograms recorded during sinus rhythm in 106 consecutive patients (including 60 retrospectively analyzed patients and 46 prospectively analyzed patients) who underwent successful radiofrequency catheter ablation of a single accessory pathway were analyzed by 3 blinded observers using all 3 algorithms. The results were compared with the actual localization of accessory pathways as derived from endocardial mapping during catheter ablation. In all 106 patients, the accuracy of the 3 algorithms for 4 sites on the atrioventricular annuli (as considered by Milstein's method) was 72%, 79%, and 92% for Milstein's, Skeberis', and St. George's algorithms, respectively. For 7 sites (as considered by Skeberis' method), the accuracy was 65% (Skeberis' algorithm) and 88% (St. George's algorithm), and for 9 sites (as considered by our method) the accuracy was 86% (St. George's algorithm). In 46 prospectively analyzed patients, the accuracy of the 3 algorithms for 4 sites was 70% (Milstein's), 67% (Skeberis'), and 87% (St. George's); for 7 sites the accuracy was 61% (Skeberis') and 85% (St. George's), and for 9 sites the accuracy was 85% (St. George's). The reproducibility of St. George's and Skeberis' methods was better than that of Milstein's method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Radiofrequency catheter ablation of septal accessory atrioventricular pathways.

OBJECTIVE: Septal accessory atrioventricular pathways are recognised as being more difficult to ablate than pathways in other locations. This paper describes an experience of 48 consecutive patients with septal accessory pathways who had catheter ablation with radiofrequency current. PATIENTS AND METHODS: There were 28 male and 20 female patients, mean (SD) age 35 (17). 43 patients had a single accessory pathway and 5 patients had multiple accessory pathways. Pre-excitation was present in 37 patients, and 11 patients had concealed accessory pathways. 21 patients had had a previous electrophysiological study. Catheter ablation was undertaken with radiofrequency current delivered by a standard unipolar technique or by delivery of current across the septum (the bipolar technique). RESULTS: The median total procedure time was 167 (83) minutes including a 30-40 minute observation period after the abolition of conduction by the accessory pathway. The median total fluoroscopic time was 56 (30) minutes. 42 (88%) out of 48 patients had successful ablation of the pathway during the first session. In the six patients in whom the procedure failed, five had a midseptal pathway and one had a right anteroseptal pathway. A second attempt at ablation was made in two patients and succeeded in both. In total, 49 accessory pathways were successfully ablated in 44 (92%) out of 48 patients. The bipolar technique was used in 11 patients and succeeded in 10 patients. Standard unipolar current delivery had previously failed in seven of the 11 patients. Complications developed in two patients with a mid septal pathway (one with complete atrioventricular block and the other with a small pericardial effusion). CONCLUSION: Radiofrequency catheter ablation of septal accessory pathways is efficacious and safe. The procedure time can be shortened and success rate can be increased after improvement of the technique--that is, consideration of a bipolar approach for energy delivery in difficult cases.

Adolescent↗
PubMed1993

Radiofrequency current delivery by way of a bipolar tricuspid annulus-mitral annulus electrode configuration for ablation of posteroseptal accessory pathways.

OBJECTIVES: This report describes a novel technique for ablation of "difficult" posteroseptal pathways. BACKGROUND: Although radiofrequency ablation of accessory atrioventricular (AV) pathways is successful in > or = 90% of cases, particular difficulty may be encountered with some bypass tracts in the posteroseptal region. METHODS: In eight patients with posteroseptal accessory pathways (two concealed), radiofrequency catheter ablation using conventional unipolar current applications from favorable sites along the tricuspid or mitral annulus, or both, was unsuccessful. Subsequently, a bipolar technique was adopted, with current application between the distal electrodes of two catheters positioned against the septal region at sites of early activation along both mitral and tricuspid annuli. RESULTS: The bipolar configuration proved effective in all cases. The number of bipolar lesions required for success was one (five patients), five (two patients) and nine (one patient). In five patients, bipolar current application abolished pathway conduction using positions at which delivery of unipolar lesions had been ineffective or caused transient block. The AV or ventriculoatrial interval at successful sites varied from 20 to 65 ms, and the time from delta wave onset to local ventricular activation was zero or negative. There were no complications attributable to the bipolar technique. During follow-up of 8 to 36 weeks, pathway conduction has not recurred in any patient. CONCLUSIONS: Bipolar radiofrequency current delivery across the septal region using a tricuspid annulus-mitral annulus electrode configuration may abolish accessory pathway conduction when conventional unipolar applications have proved ineffective. The technique may reduce procedure duration, radiation exposure and overall failure rate in these problematic cases.

Adolescent↗
PubMed1993

Detection of atrial activation by intraventricular electrogram morphology analysis: a study to determine the feasibility of P wave synchronous pacing from a standard ventricular lead.

The detection of atrial activation from a standard ventricular pacing lead with standard ventricular electrodes would provide patients with VVI and VVIR pacing systems atrial rate response and atrial synchrony. In addition to potentially increasing cardiac output appropriately in these patients at rest and during moderate exercise, P wave sensing with such a device could help reduce pacemaker syndrome. In this study, unipolar signals from distal and proximal intraventricular electrodes were recorded from the right ventricular apex in 20 patients. Unipolar electrograms from 16 patients were recorded using temporary electrophysiology catheters and in four patients using permanent pacemaker leads. Approximately 3 minutes of data per patient were acquired and analyzed. After selection of a P wave template, the difference in baseline normalized area between the template and signal was calculated on a point-by-point basis. The percent of atrial depolarizations correctly detected was determined for each patient and lead configuration at the optimal threshold. Far-field P wave accuracy was better at the proximal electrode (74 +/- 25%) than at the distal electrode (57 +/- 34%) (P < 0.025). At the proximal electrode, 15/20 (75%) patients had > 70% accuracy and 11/20 (55%) patients had > 80% accuracy. At the distal electrode, 10/21 (48%) patients had > 70% accuracy and 7/21 (33%) patients had > 80% accuracy. In conclusion, far-field detection of atrial activation at the ventricular proximal electrode appears possible with sufficient accuracy to provide periods of atrial rate response and synchrony in patients with a single standard lead.

Atrioventricular Node↗
PubMed1993

Radiofrequency ablation of accessory atrioventricular pathways: predictive value of local electrogram characteristics for the identification of successful target sites.

BACKGROUND: Radiofrequency catheter ablation of accessory arterioventricular pathways has been shown to be a highly effective treatment in patients with paroxysmal superventricular tachycardia. There is, however, considerable variability in the number of attempted ablation sites, contributing to lengthy operations in some cases. The purpose of this study was to investigate the predictive value of local electrogram characteristics for the identification of successful target sites. METHODS AND RESULTS: Local bipolar electrograms from 60 patients recorded at 568 sites of attempted ablation were analysed. There were 511 sites at which ablation was guided by antegrade mapping, with 49 successful sites and 462 failed sites including 61 at which accessory pathway conduction was blocked temporarily. In multivariate analysis, the time of local ventricular activation relative to onset of the QRS complex (QRS-V interval) (p < 0.001) and the presence of a possible accessory pathway potential (p < 0.05) were found to be independent predictors of successful outcome, whereas the atrioventricular interval, atrioventricular amplitude ratio, stability of local electrogram, and presence of continuous electrical activity were not. A QRS-V interval of < or = +10 ms identified successful sites with a sensitivity of 98%, but the positive predictive accuracy was only 11%. Even a QRS-V interval of < or = 20 ms resulted in only a 24% probability of success with a sensitivity of just 18%. Combining the QRS-V interval with the presence of a possible accessory pathway potential greatly reduced the sensitivity at all cut off values, but failed to increase positive predictive accuracy above 25%. There were no significant differences in electrogram characteristics between the successful sites and the sites at which conduction of the accessory pathway was interrupted transiently. There were 57 sites (nine successful, 48 failed) at which ablation was guided by retrograde mapping, but none of the local electrogram characteristics analysed emerged as independent predictors of successful pathway ablation. CONCLUSION: Local electrogram characteristics used to guide radiofrequency catheter ablation are all associated with a low positive predictive accuracy, which significantly contributes to duration of the operation. It is unlikely that this problem will be resolved solely by modification of the mapping techniques. It could require advances in catheter technology and power sources to enable larger tissue lesions to be delivered more reliably than is possible with the equipment in current use.

Adolescent↗