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The well-defined concept of aberrant ventricular conduction was introduced over 100 years ago and, despite advances in cardiac physiology and electrophysiologic testing, it is still widely misunderstood. Aberrant ventricular conduction is due to physiologic refractoriness of the His-Purkinje system and in most cases does not reflect underlying conduction system disease. Electrophysiologically, aberrant ventricular conduction can manifest with premature atrial ectopics, the Ashman phenomenon with atrial tachyarrhythmias, concealed conduction, echo beats and with the sinus mechanism including rate dependent bundle branch block, bradycardia dependent bundle branch block and early sinus beats. It is important to recognise aberrant ventricular conduction in the context of a broad complex tachycardia, as the differentiation between supraventricular tachyarrhythmias with aberrant ventricular conduction and ventricular tachyarrhythmias carry different therapeutic and prognostic implications. This review will define the ECG footprints of aberrant ventricular conduction to allow accurate ECG interpretation. [ABSTRACT FROM AUTHOR]

Background: Mitral valve prolapse (MVP) is relatively common condition and while generally benign a small subset of patient suffers from malignant ventricular arrhythmias (MVA) and sudden cardiac death (SCD).Method and Material: We report three cases of mitral valve prolapse, mitral regurgitation and malignant ventricular arrhythmias refractory to medical therapy, who had surgical cryoablation at the time of surgery on the mitral valve.Results: During a follow-up period ranging from 3 to 11 years all three patients have remained free of ventricular arrhythmias and cryoablation lesions targeting the base of the papillary muscles have not caused any detrimental effect on the valve function.Conclusion: Surgical cryoablation of papillary muscles as described in this article should be considered in MVP who suffer from MVA, aborted SCD or frequent ventricular ectopics likely to cause LV dysfunction. [ABSTRACT FROM AUTHOR]

Ventricular arrhythmias are one of the leading causes of death in patients with a prior myocardial infarction. Implantable cardioverter-defibrillators (ICDs) are very effective in the prevention of sudden cardiac death but the risk of recurrence remains an issue since defibrillation does not alter the underlying substrate. Recurrent ICD shocks are distressing and are associated with an increase in mortality. Catheter ablation is an effective treatment for recurrent ventricular tachycardia in these patients, particularly when antiarrhythmic therapy produces side effects or is ineffective. This paper reviews the underlying mechanisms of VT in patients with a prior myocardial infarction, and the indications, strategies and outcomes of catheter ablation. [ABSTRACT FROM AUTHOR]

Contact Force During Cavotricuspid Isthmus Ablation Introduction Recurrent atrial flutter following cavotricuspid isthmus (CTI) ablation remains a significant problem. The prevalence of low contact force (CF) during CTI ablation using standard tools is unknown. Our aim was to characterize the prevalence of low CF applications when experienced operators performed CTI ablation using 'traditional' markers of contact blinded to CF measurements. Methods and Results Average CF (grams, g) and force-time integral (FTI) was analyzed in 458 lesions in 17 patients undergoing CTI ablation. The isthmus was divided into the annular, mid and caval segments for region-specific analysis. Despite 'good' contact using traditional markers, there was significant variability in CF within each isthmus segment (e.g., annular CTI 1-57 g). A high proportion of lesions had a CF <10 g (40%). Lowest CF was the annular (median 9 g), followed by the mid (12 g) and the caval CTI (18 g, P < 0.001). Sites of acute CTI re-connection had a lower average CF and FTI than nonreconnected sites (P < 0.05). Each 1 g increase in CF was associated with a 16% reduction in risk of recovered CTI conduction (95% confidence interval: 4-27%, P = 0.01). Conclusion Use of surrogate markers of 'good contact' during ablation by experienced operators in the absence of real-time CF sensing resulted in nearly half of all lesions being delivered with low CF with marked region-specific variability in CF. Low CF was implicated in longer time to achieve conduction block and increased risk of acute reconnection. These findings underscore the importance of real-time CF measurements for optimizing ablation of typical atrial flutter. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF, Glomeromycota) colonize roots of the majority of terrestrial plants. They provide essential minerals to their plant hosts and receive photosynthates in return. All major lineages of AMF harbor endobacteria classified as Mollicutes, and known as mycoplasma-related endobacteria (MRE). Except for their substantial intrahost genetic diversity and ability to transmit vertically, virtually nothing is known about the life history of these endobacteria. To understand MRE biology, we sequenced metagenomes of three MRE populations, each associated with divergent AMF hosts. We found that each AMF species harbored a genetically distinct group of MRE. Despite vertical transmission, all MRE populations showed extensive chromosomal rearrangements, which we attributed to genetic recombination, activity of mobile elements, and a history of plectroviral invasion. The MRE genomes are characterized by a highly reduced gene content, indicating metabolic dependence on the fungal host, with the mechanism of energy production remaining unclear. Several MRE genes encode proteins with domains involved in protein-protein interactions with eukaryotic hosts. In addition, the MRE genomes harbor genes horizontally acquired from AMF. Some of these genes encode small ubiquitin-like modifier (SUMO) proteases specific to the SUMOylation systems of eukaryotes, which MRE likely use to manipulate their fungal host. The extent of MRE genome plasticity and reduction, along with the large number of horizontally acquired host genes, suggests a high degree of adaptation to the fungal host. These features, together with the ubiquity of the MRE-Glomeromycota associations, emphasize the significance of MRE in the biology of Glomeromycota. [ABSTRACT FROM AUTHOR]

The life history of arbuscular mycorrhizal fungi (AMF, Glomeromycota) consists of a short asymbiotic phase when spores germinate and a longer symbiotic phase where hyphae form a network within roots and subsequently in the rhizosphere. Hyphal anastomosis contributes to colony formation, yet this process has been studied mostly in the asymbiotic phase rather than in mycorrhizal plants because of methodological limitations. We sought to compare patterns of anastomosis during each phase of fungal growth by measuring hyphal fusions in genetically identical and different single spore isolates of Rhizophagus clarus from different environments and geographic locations. These isolates were genotyped with two anonymous markers of microsatellite-flank-ing regions. Anastomosis of hyphae from germinating spores was examined in axenic Petri dishes. A rhizohyphatron consisting of agar-coated glass slides bridging single or paired mycorrhizal sorghum plants allowed evaluation of anastomosis of symbiotic hyphae. Anastomosis of hyphae within a colony, defined here as a mycelium from an individual germinating spore or from mycorrhizal roots of one plant, occurred with similar frequencies (8-38%). However, anastomosis between paired colonies was observed in germinating spores from either genetically identical or different isolates, but it was never detected in symbiotic hyphae. The frequency of anastomosis in asymbiotic hyphae from paired interactions was low, occurring in fewer than 6% of hyphal contacts. These data suggest that anastomosis is relatively unconstrained when interactions occur within a colony but is confined to asymbiotic hyphae when interactions occur between paired colonies. This pattern of behavior suggests that asymbiotic and symbiotic phases of mycelium development by R. clarus may differ in function. Anastomosis in the asymbiotic phase may provide brief opportunities for gene flow between populations of this and possibly other AMF species. [ABSTRACT FROM AUTHOR]

Abstract: A putative mutant of Scutellospora heterogama has been maintained for 19 pot culture generations over 15y. The mutant differed phenotypically from the wild-type parental lineage in characteristics of the spore wall: albino versus pigmented red-brown color, high plasticity in acidic mutants versus rigid and finely laminate, deep red-purple reaction versus no reaction in Melzer''s reagent, respectively. This variation was equivalent to or greater than that between any two species in Scutellospora or any other genus in Glomeromycota. Comparison of spore ontogenesis revealed that the terminal (mature) state of the albino mutant was similar to a transient intermediate stage in the wild-type. The albino phenotype, therefore, did not result from emergence of a unique morphological innovation. Rather, it arose from a mutation that led to premature termination of spore ontogenesis so that a unique transient juvenile stage became permanent in mature spores. Because this mutation was homogeneous in all progeny populations, it is hypothesized to be a recessive trait expressed only after the allele was distributed in all nuclei of the fungal thallus. Sampling of the genomes of the putative mutant and wild-type isolates by microsatellite-primed PCR suggested a local mutation. The profile of the mutant was identical to that of the wild-type parent and was 60–97 % similar to those of four other S. heterogama isolates. Phylogenetic analysis of the D1–D2 domains of the 25S rRNA gene and a β-tubulin gene with and without three variable introns placed the albino mutant solidly within the S. heterogama clade. These results suggest that stability of morphological traits is not a suitable criterion by itself to recognize species. The albino phenotype was a discrete and heritable mutation that became fixed in a population and was stable through time and space. In the absence of negative selection, this mutation could persist, disperse and then be misinterpreted as a new species in nature. Genetic markers expose this mutation as a population-level variant and therefore of no macroevolutionary significance. Assessment of genetic divergence amongst multiple isolates is important in ascertaining the contribution of morphological characters toward recognition of species in glomeromycotan clades. [Copyright &y& Elsevier]

Monomorphic ventricular tachycardia (VT) can arise from multiple different ventricular locations in the context of several different underlying myocardial substrates. Despite this variability, the surface 12-lead electrocardiograph (ECG) has proven to be a robust and reproducible initial mapping tool that can provide useful information in localizing the origin of both focal and reentrant forms of VT. The second part of this review series will look at the use of the ECG in mapping the various forms of VT encountered in clinical practice. [ABSTRACT FROM AUTHOR]

Ventricular Depolarization Abnormality in Sarcoidosis. A 47-year-old man presented with sustained monomorphic ventricular tachycardia of right ventricular origin. Surface ECG recorded during sinus rhythm showed a bizarre“double QRS” pattern. Biventricular cardiomyopathy was found with predominant right ventricular involvement, due to cardiac sarcoidosis. Electroanatomic mapping was used to characterize the right ventricular substrate abnormalities and to decipher the specific activation abnormalities responsible for the ECG findings.(J Cardiovasc Electrophysiol, Vol. 15, pp. 1091-1094, September 2004) [ABSTRACT FROM AUTHOR]

Conduction Across the Crista Terminalis . Introduction: Focal atrial fibrillation (AF) may initiate with an irregular rapid burst of atrial ectopic (AE) activity from a pulmonary vein (PV) focus, but how AF is maintained it is not known. The crista terminalis (CT) is an important line of block in atrial flutter (AFL), but its role in AF has not been determined. The aim of this study was to examine the conduction properties of the CT during onset of AF. Methods and Results: In 10 patients (mean age 38 ± 8 years), we analyzed conduction across the CT during onset of focal AF from an arrhythmogenic PV and during pacing from the same PV at cycle lengths of 700 and 300 ms. A 20-pole catheter was positioned on the CT using intracardiac echocardiography. In 10 control patients with no history of AF, we analyzed conduction across the CT during pacing from the distal coronary sinus at 700 and 300 ms. In all 10 AF patients, AF was initiated with 1 to 9 AE beats (median 5) from a PV. During sinus rhythm, there were no split components (SC) recorded on the CT. During PV AE activity, discrete SC were recorded on the CT in all patients over 6.3 ± 0.9 bipoles (3.7 ± 0.3 cm). Maximal splitting of SC was 66 ± 31 ms (37–139). There was an inverse relationship between AE coupling intervals and the degree of splitting between SC in all patients. Degeneration to AF was preceded by progressive decrement across the CT. SC were recorded during PV pacing at 700 and 300 ms (maximal distance between SC of 24 ± 3 ms and 43 ± 5 ms, respectively, P < 0.001). Maximum SC at CT in controls was 13 ± 8 ms at 700 ms (P = 0.06 vs AF patients) and 16 ± 9 ms at 300 ms (P < 0.01 vs AF patients). Conclusion: (1) These observations provide evidence of anisotropic, decremental conduction across the CT during onset of focal AF and during pacing from the same PV. A line of functional conduction block develops along this anatomic structure (CT). Whether this line of block acts as an initiator of AF or simply contributes passively to nonuniform fibrillatory conduction is unknown. (2) In some patients with focal AF, development of conduction block along the CT may provide a substrate for typical AFL. (J Cardiovasc Electrophysiol, Vol. 15, pp. 1-7, August 2004) [ABSTRACT FROM AUTHOR]

Intracardiac Echocardiography of the Flutter Isthmus. Introduction: Cavotricuspid isthmus (CTI) topography includes ridges, pouches, recesses, and trabeculations. These features may limit the success of radiofrequency ablation (RFA) of typical atrial flutter (AFL). The aim of this study was to assess the utility of phased-array intracardiac echocardiography (ICE) for imaging the CTI and monitoring RFA of AFL. Methods and Results: Fifteen patients (mean age 64 ± 9 years) underwent ICE assessment (imaging frequency 7.5–10 MHz) before and after RFA of AFL. The ICE catheter was positioned at the inferior vena cava-right atrial junction and the following parameters were measured: (1) CTI length from the tricuspid valve to the eustachian ridge; (2) extent of CTI pouching; and (3) thickness pre/post RFA of the anterior, mid, and posterior CTI. CTI length was 35 ± 6 mm at end-ventricular systole but shorter (30 ± 6 mm) and more pouched at end-ventricular diastole (P = 0.02) . A pouch or recess was seen in 11 of 15 patients (mean depth 6 ± 2 mm ). The septal CTI was more pouched than the lateral CTI, but the latter had more prominent trabeculations. Trabeculations were seen in 10 of 15 patients, and at these locations the CTI was 4.6 ± 1 mm thick. Anterior, mid, and posterior CTI thickness pre-RFA was 4.1 ± 0.8, 3.3 ± 0.5 , and 2.7 ± 0.9 mm , respectively ( P < 0.001 by analysis of variance). ICE guided RFA away from unfavorable CTI features (recesses/thick trabeculations). RFA applications created discrete CTI lesions that coalesced, forming diffuse CTI swelling. Post-RFA thickness was as follows: anterior 4.8 ± 0.8 mm (P = NS vs pre); mid 3.8 ± 0.8 mm (P = 0.05 vs pre) ; and posterior 3.8 ± 0.8 mm (P = 0.02 vs pre) . Conclusion: Phased-array ICE permits novel real-time CTI imaging with excellent endocardial resolution and may facilitate RFA of AFL. (J Cardiovasc Electrophysiol, Vol. 14, pp. 591-597, June 2003). [ABSTRACT FROM AUTHOR]

We compared transesophageal and phased-array intracardiac echocardiography (TEE/ICE) for the 2-dimensional and spectral Doppler assessment of left atrial (LA) mechanical function. TEE is commonly used to assess LA body and LA appendage mechanical function in patients who are undergoing radiofrequency ablation of typical atrial flutter. Fifteen patients underwent TEE and ICE imaging before and after ablation of typical atrial flutter. The following parameters were measured: (1) LA appendage emptying velocity and fractional area change, (2) severity of LA spontaneous echo contrast (graded 0 to 4), (3) maximal inflow velocity of the left and right upper pulmonary veins, and (5) maximal mitral valve E- and A-wave inflow velocities in sinus rhythm. Diagnostic quality imaging was achieved in all patients with TEE and ICE. Comparing TEE and ICE, the following absolute values and linear correlation coefficient (R) were obtained: preablation LA appendage emptying velocity: 0.45 ± 0.21 versus 0.44 ± 0.21 m/s (r = 0.95, p = <0.001); postablation LA appendage velocity: 0.33 ± 0.24 versus 0.34 ± 0.24 m/s (r = 0.97, p <0.001); LA appendage fractional area change: 35.3 ± 13.7 versus 35.9 ± 17.1% (r = 0.81, p <0.001); left upper/right upper pulmonary vein inflow velocity: 0.50 ± 0.17/0.49 ± 0.18 versus 0.51 ± 0.17/0.47 ± 0.20 m/s (r = 0.93/0.90, p <0.001); mitral valve E/A wave: 0.66 ± 0.14/0.31 ± 0.14 versus 0.69 ± 0.17/0.35 ± 0.23 (r = 0.84/0.97, p <0.002); LA spontaneous echo contrast (pre- and postablation): 1.1 ± 1.2/1.3 ± 1.2 versus 1.2 ± 1.3/1.4 ± 1.3 (r = 0.92/0.90, p <0.001). No patients were identified with LA appendage thrombus. Thus, TEE and phased-array ICE provided equivalent imaging data with high statistical correlation. ICE may be an imaging alternative to TEE in the evaluation of a “stunned” left atrium. [Copyright &y& Elsevier]

OBJECTIVESThis study was designed to determine the sensitivity and specificity of concealed entrainment (CE) for the identification of a critical isthmus in the atrium.BACKGROUNDIsthmus identification during entrainment mapping of macro-reentrant atrial tachycardia (MRAT) relies on the demonstration of CE.METHODSUsing the model of typical atrial flutter, entrainment was performed in 10 patients at four rates (flutter cycle length [FCL] minus 10/20/30/40 ms) from seven sites: isthmus entrance/exit, low lateral/high lateral/high septal right atrium and proximal/distal coronary sinus. Surface 12-lead electrocardiogram fusion was evaluated by three observers blind to patient status. The extent of antidromic penetration (AP) was measured off the pacing catheter positioned around the tricuspid annulus.RESULTSThe sensitivity for CE identifying any isthmus site was greatest at FCL−10 (100%), but the specificity was poor (54%). Conversely, specificity was greatest at FCL−40 (98%), but the sensitivity was poor (65%), with manifest entrainment (ME) observed from the isthmus entrance in 70% of episodes. At FCL−30, sensitivity (85%) and specificity (90%) were “balanced,” but CE still resulted during entrainment from a non-isthmus site in five of 10 patients. Antidromic penetration increased with pacing CL shortening (p < 0.001) and correlated with the development of ME (p < 0.001). Antidromic penetration was significantly blunted from the isthmus exit compared to all other sites (p = 0.003).CONCLUSIONSThe sensitivity and specificity of CE for identifying an isthmus in the atrium are critically dependent on the pacing rate and the precise anatomic pacing site within the isthmus. These findings may have implications for the use of entrainment in the mapping of unknown MRAT circuits. [Copyright &y& Elsevier]

Shows that the association of arbuscular mycorrhizal fungi with particular host plants are positively correlated with the sporulation rates observed on the hosts in laboratory microcosm experiments. Influence of the time of harvest; Host-dependent differences in fungal growth rates; Estimates of fungal species richness; Maintenance of fungal species diversity.

Key Points: Question: Does adding posterior wall isolation (PWI) to pulmonary vein isolation (PVI) improve success in patients with persistent atrial fibrillation (AF) undergoing first-time catheter ablation? Findings: In this randomized clinical trial that included 338 patients with persistent AF, there was no significant difference in 12-month freedom from recurrent atrial arrhythmia after a single procedure and without antiarrhythmic medication among those with PVI and PWI compared with PVI alone (52.4% vs 53.6%, respectively; hazard ratio, 0.99). Meaning: Among patients with persistent AF undergoing first-time catheter ablation, the addition of PWI to PVI did not improve freedom from atrial arrhythmias compared with PVI alone. Importance: Pulmonary vein isolation (PVI) alone is less effective in patients with persistent atrial fibrillation (AF) compared with paroxysmal AF. The left atrial posterior wall may contribute to maintenance of persistent AF, and posterior wall isolation (PWI) is a common PVI adjunct. However, PWI has not been subjected to randomized comparison. Objective: To compare PVI with PWI vs PVI alone in patients with persistent AF undergoing first-time catheter ablation. Design, Setting, and Participants: Investigator initiated, multicenter, randomized clinical trial involving 11 centers in 3 countries (Australia, Canada, UK). Symptomatic patients with persistent AF were randomized 1:1 to either PVI with PWI or PVI alone. Patients were enrolled July 2018-March 2021, with 1-year follow-up completed March 2022. Interventions: The PVI with PWI group (n = 170) underwent wide antral pulmonary vein isolation followed by posterior wall isolation involving linear ablation at the roof and floor to achieve electrical isolation. The PVI-alone group (n = 168) underwent wide antral pulmonary vein isolation alone. Main Outcomes and Measures: Primary end point was freedom from any documented atrial arrhythmia of more than 30 seconds without antiarrhythmic medication at 12 months, after a single ablation procedure. The 23 secondary outcomes included freedom from atrial arrhythmia with/without antiarrhythmic medication after multiple procedures, freedom from symptomatic AF with/without antiarrhythmic medication after multiple procedures, AF burden between study groups at 12 months, procedural outcomes, and complications. Results: Among 338 patients randomized (median age, 65.6 [IQR, 13.1] years; 76.9% men), 330 (97.6%) completed the study. After 12 months, 89 patients (52.4%) assigned to PVI with PWI were free from recurrent atrial arrhythmia without antiarrhythmic medication after a single procedure, compared with 90 (53.6%) assigned to PVI alone (between-group difference, –1.2%; hazard ratio [HR], 0.99 [95% CI, 0.73-1.36]; P =.98). Of the secondary end points, 9 showed no significant difference, including freedom from atrial arrhythmia with/without antiarrhythmic medication after multiple procedures (58.2% for PVI with PWI vs 60.1% for PVI alone; HR, 1.10 [95% CI, 0.79-1.55]; P =.57), freedom from symptomatic AF with/without antiarrhythmic medication after multiple procedures (68.2% vs 72%; HR, 1.20 [95% CI, 0.80-1.78]; P =.36) or AF burden (0% [IQR, 0%-2.3%] vs 0% [IQR, 0%-2.8%], P =.47). Mean procedural times (142 [SD, 69] vs 121 [SD, 57] minutes, P <.001) and ablation times (34 [SD, 21] vs 28 [SD, 12] minutes, P <.001) were significantly shorter for PVI alone. There were 6 complications for PVI with PWI and 4 for PVI alone. Conclusions and Relevance: In patients undergoing first-time catheter ablation for persistent AF, the addition of PWI to PVI alone did not significantly improve freedom from atrial arrhythmia at 12 months compared with PVI alone. These findings do not support the empirical inclusion of PWI for ablation of persistent AF. Trial Registration: anzctr.org.au Identifier: ACTRN12616001436460 This randomized clinical trial compares pulmonary vein isolation (PVI) vs PVI with posterior wall isolation for achieving freedom from atrial arrhythmia in adult patients with persistent atrial fibrillation undergoing first-time catheter ablation in Australia, the UK, and Canada. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (phylum Glomeromycota) are among the oldest and most successful symbionts of land plants. With no evidence of sexual reproduction, their evolutionary success is inconsistent with the prediction that asexual taxa are vulnerable to extinction due to accumulation of deleterious mutations. To explore why Glomeromycota defy this prediction, we studied ribosomal RNA (rRNA) gene evolution in the Claroideoglomus lineage and estimated effective population size, Ne, in C. etunicatum. We found that rRNA genes of these fungi exhibit unusual and complex patterns of molecular evolution. In C. etunicatum, these patterns can be collectively explained by an unexpectedly large Ne combined with imperfect genome-wide and population-level rRNA gene repeat homogenization. The mutations accumulated in rRNA gene sequences indicate that natural selection is effective at purging deleterious mutations in the Claroideoglomus lineage, which is also consistent with the large Ne of C. etunicatum. We propose that in the near absence of recombination, asexual reproduction involving massively multinucleate spores typical for Glomeromycota is responsible for the improved efficacy of selection relative to drift. We postulate that large effective population sizes contribute to the evolutionary longevity of Glomeromycota. [ABSTRACT FROM AUTHOR]

Many eukaryotes interact with heritable endobacteria to satisfy diverse metabolic needs. Some of these interactions are facultative symbioses, in which one partner is not essential to the other. Facultative symbioses are expected to be transitional stages along an evolutionary trajectory toward obligate relationships. We tested this evolutionary theory prediction in Ca. Glomeribacter gigasporarum, nonessential endosymbionts of arbuscular mycorrhizal fungi (Glomeromycota). We found that heritable facultative mutualisms can be both ancient and evolutionarily stable. We detected significant patterns of codivergence between the partners that we would only expect in obligate associations. Using codiverging partner pairs and the fungal fossil record, we established that the Glomeromycota-Glomeribacter symbiosis is at least 400 million years old. Despite clear signs of codivergence, we determined that the Glomeribacter endobacteria engage in recombination and host switching, which display patterns indicating that the association is not evolving toward reciprocal dependence. We postulate that low frequency of recombination in heritable endosymbionts together with host switching stabilize facultative mutualisms over extended evolutionary times. [ABSTRACT FROM AUTHOR]

To report the major complication rate associated with pulmonary vein antral isolation (PVAI) in a consecutive series of 500 patients from a single center. Catheter ablation for atrial fibrillation (AF) is an established procedure for refractory AF. However, the risk of major complications has been reported to range from 3.9% to 4.5% and continues to represent a cause for concern. We hypothesized that these studies may have overestimated the rate of major complications associated with PVAI in patients with a low prevalence of structural heart disease (SHD). Data were prospectively collected from 500 consecutive AF ablation procedures on 424 patients (mean age 55 ± 11 years, 79% men, paroxysmal AF-80% and persistent AF-20%, CHADS scores of 0, 1, 2, 3 present in 64%, 28%, 7%, 1%, respectively), performed between July 2006 and September 2009. All procedures were performed under general anesthesia with intraoperative transesophageal echo. PVAI was performed using a nonfluoroscopic mapping system with an endpoint of PV isolation. Adjunctive left atrial ablation was performed in 21% of patients only. Major complications were defined from a compilation of those reported in 5 prior studies reporting complications. In 500 procedures, there were no instances of death, stroke/TIA, cardiac tamponade, atrioesophageal fistula, or PV stenosis. Major complications occurred in 4 procedures (0.8%): esophageal hematoma (TEE probe)-2; pharyngeal trauma-1; and retroperitoneal hematoma-1. AF ablation can be performed safely in young patients without structural heart disease with a low risk (<1%) of major complications when using a strategy of PVAI. (J Cardiovasc Electrophysiol, Vol. 22, pp. 163-168, February 2011) [ABSTRACT FROM AUTHOR]

A considerable amount of phenotypic, genetic and symbiotic functional variability has been documented in arbuscular mycorrhizal fungi (AMF). However, little is known about whether distinct AMF ecotypes have evolved within their geographic range. We tested the hypothesis that AMF growing at temperatures closer to those prevalent within their origin would benefit their host and grow more than isolates distant from their native conditions. For each of six AMF species, we chose pairs of isolates that originated from distant areas with contrasting climates. Each isolate was grown in association with two grass species of different thermal optima at two temperature settings. Thus, we also tested whether AMF from different climatic origins were dependent on the thermal adaptation of the host plant species or to temperature per se. Although fungal growth was not directly affected by temperature, we found that AMF isolates originating from contrasting climates consistently and differentially altered plant growth. Our results suggest that AMF from contrasting climates have altered symbiotic function, thus linking an abiotic factor to ecotypic differentiation of putatively important symbionts. [ABSTRACT FROM AUTHOR]

Prevalence of Vagal Paroxysmal Atrial Fibrillation. Introduction: The prevalence of vagal and adrenergic atrial fibrillation (AF) and the success rate of pulmonary vein isolation (PVI) are not well defined. We investigated the prevalence of vagal and adrenergic AF and the ablation success rate of antral pulmonary vein isolation (APVI) in patients with these triggers compared with patients with random AF. Methods and Results: Two hundred and nine consecutive patients underwent APVI due to symptomatic drug refractory paroxysmal AF. Patients were diagnosed as vagal or adrenergic AF if >90% of AF episodes were related to vagal or adrenergic triggers; otherwise, a diagnosis of random AF was made. Clinical, electrocardiogram (ECG), and Holter follow-up was every 3 months in the first year and every 6 months afterward and for symptoms. Of 209 patients, 57 (27%) had vagal AF, 14 (7%) adrenergic AF, and 138 (66%) random AF. Vagal triggers were sleep (96.4%), postprandial (96.4%), late post-exercise (51%), cold stimulus (20%), coughing (7%), and swallowing (2%). At APVI, 94.3% of patients had isolation of all veins. Twenty-five (12%) patients had a second APVI. At a follow-up of 21 ± 15 months, the percentage of patients free of AF was 75% in the vagal group, 86% in the adrenergic group, and 82% for random AF (P = 0.51). Conclusion: In patients with PAF and no structural heart disease referred for APVI, vagal AF is present in approximately one quarter. APVI is equally effective in patients with vagal AF as in adrenergic and random AF. (J Cardiovasc Electrophysiol, Vol. 21, pp. 489-493, May 2010) [ABSTRACT FROM AUTHOR]

The arbuscular mycorrhizal fungus Glomus mosseae is commonly found in agricultural fields. The cosmopolitan species is found in Africa, Europe, America, Asia and Australia. Three hypotheses may explain this worldwide distribution: First, speciation occurred before the continents separated 120 Ma; second, the distribution is a result of human-mediated dispersal related to agriculture and finally, the morphologically defined species may encompass several local endemic species. To test these hypotheses, three genes were sequenced from 82 isolates of G. mosseae originating from six continents and the resulting sequences analysed for geographical subdivision and estimation of migration between continents. Coalescent analyses estimated divergence and age of mutations. Bayesian coalescent modelling was used to reveal important past population changes in the global population. The sequence data showed no geographical structure, with identical genotypes found on different continents. Coalescence analyses indicated a recent diversification in the species, and the data could be explained by a recent population expansion in G. mosseae. The results of this study suggest that speciation and the range expansion happened much later than continental spread and that human activity may have had a major impact on the dispersal and the population structure of the fungus. [ABSTRACT FROM AUTHOR]

Background: Catheter ablation is highly effective for atrioventricular nodal re‐entrant tachycardia (AVNRT). Generally junctional rhythm (JR) is an accepted requirement for successful ablation however there is a lack of detailed prospective studies to determine the characteristics of JR and the impact on slow pathway conduction. Methods: Multicentre prospective observational study evaluating the impact of individual radiofrequency (RF) applications in typical AVNRT (slow/fast). Characteristics of JR during ablation were documented and detailed testing was performed after every RF application to determine outcome. Procedural success was defined as ≤1 AV nodal echo. Results: Sixty‐seven patients were included (mean age 53 ± 18years, 57% female and a history of SVT 2.9 ± 4.7 years). RF (50w, 60°) ablation for AVNRT was applied in 301 locations with JR in 178 (59%). Successful slow pathway modification was achieved in 66 (99%) patients with slow pathway block in 30 (46%). Success was associated with JR in all patients. Success was achieved in six patients with RF < 10 s. There was no significant difference in the CL of JR during RF between effective (587 ± 150 ms) versus ineffective (611 ± 193 ms, p =.4) applications. Inadvertent junctional beat‐atrial (JA) block with immediate termination of RF was observed in 19 (28%) patients with AVNRT no longer inducible in 14 (74%). Freedom from SVT was achieved in 66 (99%) patients at a mean follow up of 15 ± 6 months. Conclusion: In this prospective study, JR was required during RF for acute success in AVNRT. Cycle length of JR during RF was not predictive of success. Although unintended JA block during faster JR was associated with slow pathway block, this is a precursor to fast pathway block and should not be intentionally targeted. [ABSTRACT FROM AUTHOR]

Keywords: amplicon sequencing; bioinformatics; eDNA; Glomeromycota; large subunit EN amplicon sequencing bioinformatics eDNA Glomeromycota large subunit 3048 3052 5 02/19/21 20210315 NES 210315 Background Arbuscular mycorrhizal fungi (AMF - phylum Glomeromycota) form symbioses with most plant species worldwide and play critical roles in plant nutrient and water uptake, pathogen resistance and soil aggregation (Smith & Read, 2008; Delavaux I et al i ., 2017; Brundrett & Tedersoo, 2018). Because AMF community composition influences ecological function (van der Heijden I et al i ., 1998; Vogelsang I et al i ., 2006; Koziol I et al i ., 2018), understanding patterns of AMF composition is a research priority. Reference database and pipeline We present a current curated database and reference tree using AMF sequences from several sources: a subset of sequences published by Krüger I et al i . GLO:F0R/15mar21:nph17080-fig-0001.jpg PHOTO (COLOR): 1 Arbuscular mycorrhizal fungi (AMF) large subunit (LSU) backbone tree. [Extracted from the article]

Background: Multipolar catheters provide high‐density mapping which may reduce the procedural duration and improve the success of catheter ablation (CA) for focal arrhythmias. The high‐density grid (HDG) catheter is a 16 electrode mapping catheter with bipole recordings at orthogonal splines. The aim of this study is to compare the clinical and procedural features from a cohort who underwent CA for focal arrhythmias using multipolar mapping (MPM) with age and case‐matched cohort using point‐by‐point (PbyP) mapping. Methods: Consecutive patients undergoing CA for focal arrhythmias between October 2018 and January 2020 guided by MPM were compared with PbyP mapping with the ablation catheter over a similar period. Demographics, procedural features, and outcomes were compared. Results: A total of 54 patients (27 in MPM vs. 27 in PbyP mapping) underwent CA for 68 focal arrhythmias (26 atrial and 42 ventricular). In the MPM group, the electrogram at the successful site was significantly earlier (39 ± 11 ms) than in the PbyP group (33 ± 7 ms; p =.02). In the MPM group, the mapping time (35 ± 24 vs. 53 ± 31 min in PbyP; p =.03) and procedural duration (126 ± 42 vs. 153 ± 39 min in PbyP; p =.02) were significantly shorter. There was no significant difference in radiofrequency and fluoroscopy times, acute procedural success, and arrhythmia recurrence. Conclusion: MPM with the HDG catheter for focal tachycardias identified earlier activation times and was associated with shorter mapping and procedure duration with equivalent success to PbyP mapping. [ABSTRACT FROM AUTHOR]

This study reports that patients with large body mass indexes (BMIs) and long-duration atrial fibrillation (AF) have greater defibrillation thresholds than patients with normal BMIs and AF of short duration. BMI is an independent predictor of defibrillation thresholds in patients with longer duration AF in whom external cardioversion has failed. [Copyright &y& Elsevier]

Abstract Background The key drivers of symptom severity and health-related quality of life (hr-QOL) in patients with atrial fibrillation (AF) remain unclear. We aimed to determine the relative contribution to symptom severity and hr-QOL of clinical factors including left ventricular (LV) diastolic function and ventricular rate control during AF and of psychological functioning. Methods Seventy-eight consecutive patients with symptomatic AF and preserved LV systolic function underwent detailed evaluation of i) AF symptom severity and hr-QOL; ii) clinical factors including left ventricular (LV) diastolic function, AF burden, and ventricular rate during AF and iii) state and trait aspects of psychological functioning. Results Moderate-to-severe AF-related symptoms were reported by 64% of the study population whilst 36% reported no more than mild symptoms. Worse symptom severity was associated with a higher score on the Perceived Stress Scale (16.7 ± 4.4 vs. 5.4 ± 4.4, p < 0.0001) and higher prevalence of the Type D Personality (20/50 vs. 4/28, p = 0.012). In multivariable models, only a predisposition to subjectively appraise life situations as stressful (higher PSS score) and a personality with a higher degree of negative affectivity and social inhibition (higher TDPS score) were independent predictors of higher AF symptom severity and poorer hr-QOL. No clinical factors including AF burden, ventricular rates during AF or LV diastolic function were significant predictors of AF-specific symptoms or hr-QOL. Conclusion In a tertiary AF population with preserved LV systolic function, only psychological functioning consistently predicts both AF-related symptoms and hr-QOL. LV diastolic function, AF burden, and ventricular rate during AF are not independent predictors. Highlights In a tertiary AF population, in analyses incorporating both clinical variables and variables of psychological function: • LV diastolic function does not predict AF symptom severity or hr-QOL. • Ventricular rates during AF do not predict AF symptom severity or hr-QOL. • AF burden or persistence do not predict AF symptom severity or hr-QOL. • Psychological function, specifically stress perception and a type D personality, is the dominant predictor of symptom severity and hr-QOL. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Cardiac magnetic resonance (CMR)‐identified late gadolinium enhancement (LGE), representing regional fibrosis, is often used to predict ventricular arrhythmia risk in nonischemic cardiomyopathy (NICM). However, LGE is more closely correlated with sustained monomorphic ventricular tachycardia (SMVT) than ventricular fibrillation (VF). We characterized CMR findings of ventricular LGE in VF survivors. Methods: We examined consecutively resuscitated VF survivors undergoing contrast‐enhanced 1.5T CMR between 9/2007 and 7/2016. We excluded coronary artery disease, hypertrophic cardiomyopathy, amyloid, sarcoid, arrhythmogenic right ventricular cardiomyopathy, and channelopathy. Preexisting implantable cardioverter‐defibrillator (ICD) was a CMR contraindication. VF patients were divided into three groups: (1) NICM, (2) left ventricular (LV) dilatation with normal LV ejection fraction (LVEF), and (3) normal LV size and LVEF. Two groups of NICM patients with and without SMVT were examined for comparison. Results: We analyzed 87 VF patients, and found that LGE was seen in 8/22 (36%) with NICM (LVEF 38 ± 11%, LV end‐diastolic volume index [LVEDVI] 134 ± 68 mL/BSA), 11/40 (28%) with LV dilatation and normal LVEF (LVEDVI 103 ± 17 mL/BSA), 4/25 (16%) with normal LV size and LVEF. Incidence of LGE in NICM patients without prior ventricular tachycardia/VF (LVEF 36 ± 12%, LVEDVI 141 ± 46 mL/body surface area [BSA]) was 117/277 and was not lower than those with VF and NICM (42% vs 36%; P = 0.59). By contrast, 22/37 NICM patients with SMVT (LVEF 42 ± 11%, LVEDVI 123 ± 48 mL/BSA) were LGE‐positive (59% NICM‐SMVT vs 36% NICM‐VF; P = 0.04). Conclusion: Most VF survivors with a diagnosis of NICM did not have LGE on CMR and would not have met primary prevention ICD criteria based on LVEF. Absence of LGE may not portend a benign prognosis in NICM. Novel strategies for determining SCD risk in this cohort are required. [ABSTRACT FROM AUTHOR]

Background: Despite technological advances, studies continue to report high complication rates for atrial fibrillation (AF) ablation. We sought to review complication rates for AF ablation at a high-volume centre over a 14-year period and identify predictors of complications.Methods: We reviewed prospectively collected data from 2750 consecutive AF ablation procedures at our institution using radiofrequency energy (RF) between January 2004 and May 2017. All cases were performed under general anaesthetic with transoesophageal echocardiography (TEE), 3D-mapping and an irrigated ablation catheter. Double transseptal puncture was performed under TEE guidance. All patients underwent wide antral circumferential isolation of the pulmonary veins (30W anteriorly, 25W posteriorly) with substrate modification at operator discretion.Results: Of 2255 initial and 495 redo procedures, ablation strategies were: pulmonary vein isolation (PVI) only 2097 (76.3%), PVI+ LA lines 368 (13.4%), PVI+posterior wall 191 (6.9%), PVI+cavotricuspid isthmus 277 (10.1%). There were 23 major (0.84%) and 20 minor (0.73%) complications. Cardiac tamponade (five cases - 0.18%) and phrenic nerve palsy (one case - 0.04%) rates were very low. Major vascular complications necessitating surgery or blood transfusion occurred in five patients (0.18%). There were no cases of death, permanent disability, atrio-oesophageal fistulae or symptomatic pulmonary vein (PV) stenosis, although there were five TEE probe-related complications (0.18%). Female gender (OR 2.14; 95% CI 1.07-4.26) but not age >70 (OR 1.01) was the only multivariate predictor of complications.Conclusions: Atrial fibrillation ablation performed at a high-volume centre using RF can be achieved with a low major complication rate in a representative AF population over a sustained period of time. [ABSTRACT FROM AUTHOR]

The mycoplasma-related endobacteria ( MRE), representing a recently discovered lineage of Mollicutes, are widely distributed across arbuscular mycorrhizal fungi ( AMF, Glomeromycota). AMF colonize roots of most terrestrial plants and improve plant mineral nutrient uptake in return for plant-assimilated carbon. The role of MRE in the biology of their fungal hosts is unknown. To start characterizing this association, we assessed partitioning of MRE genetic diversity within AMF individuals and across the AMF phylogeographic range. We further used molecular evolution patterns to make inferences about MRE codivergence with AMF, their lifestyle and antiquity of the Glomeromycota- MRE association. While we did not detect differentiation between MRE derived from different continents, high levels of diversity were apparent in MRE populations within AMF host individuals. MRE exhibited significant codiversification with AMF over ecological time and the absence of codivergence over evolutionary time. Moreover, genetic recombination was evident in MRE. These patterns indicate that, while MRE transmission is predominantly vertical, their complex intrahost populations are likely generated by horizontal transmission and recombination. Based on predictions of evolutionary theory, we interpreted these observations as a suggestion that MRE may be antagonists of AMF. Finally, we detected a marginally significant signature of codivergence of MRE with Glomeromycota and the Endogone lineage of Mucoromycotina, implying that the symbiosis between MRE and fungi may predate the divergence between these two groups of fungi. [ABSTRACT FROM AUTHOR]

Gender and Atrial Electrophysiology Background Gender-based differences in the clinical nature of cardiac arrhythmias such as atrial fibrillation (AF) are well established. Objective The purpose of this study was to identify any such gender-based differences in the underlying pulmonary vein and atrial substrate. Methods and Results Thirty-eight patients with no history of AF undergoing catheter ablation for supraventricular tachycardia (SVT) and 55 with paroxysmal or persistent AF undergoing catheter ablation of AF underwent detailed electroanatomic mapping of the pulmonary veins and atria. Refractory periods in multiple locations, sinus node function, endocardial bipolar voltage, pulmonary vein and atrial conduction, and bipolar electrogram complexity were analyzed. There were no significant between-gender differences in age or other clinical variables known to impact on the atrial or pulmonary vein substrate. In neither the AF nor the non-AF cohorts were there any significant differences in atrial or pulmonary vein refractoriness, sinus node function, any measure of PV electrophysiology, or any measure of atrial electrophysiology. Conclusion No systematic between-gender differences were observed in the PV or atrial substrate either in those with or without a history of AF, with a similar prevalence of the cardiovascular comorbidities frequently associated with atrial remodeling and AF seen in both male and female groups. [ABSTRACT FROM AUTHOR]

Catheter-Tissue Contact Force Determines Atrial Electrogram Characteristics Introduction Electrogram (EGM) characteristics are used to infer catheter-tissue contact. We examined if (a) atrial EGM characteristics predicted CF and (b) compared the value of CF versus other surrogates for predicting lesion efficacy. Methods and Results Twelve paroxysmal AF patients underwent pulmonary vein isolation using radiofrequency (RF) ablation facilitated by a novel CF-sensing catheter. Operators were blinded to CF. EGM amplitude, width, and morphology were measured pre- and post-RF. At each RF site, average CF, force-time integral (FTI), impedance fall, time to impedance plateau, maximum power, catheter tip temperature, and total energy delivered were recorded. An effective lesion was defined based on previously validated EGM criteria for transmural lesions. There was a moderate correlation between CF and EGM amplitude (r = 0.19) and EGM width (r = −0.22). Pre-RF, EGM amplitude, and width had modest to poor discriminative capacity for identifying preablation CF (e.g., EGM amplitude identified CF>20 g with sensitivity and specificity of 67% and 60%, respectively). Preablation CF, FTI, and total energy delivered during RF were the only independent predictors of effective lesion formation. Neither pre-RF EGM amplitude/width nor power, temperature, and impedance changes during RF predicted effective lesion formation. An average CF >16 g or FTI >404 g*s had excellent sensitivity and specificity (>80%) for identifying an effective lesion. Conclusions EGM characteristics do not reliably predict either CF before the onset of RF, nor do they predict the likelihood of an effective lesion. CF parameters were superior to power, temperature, and impedance changes during RF in predicting lesion efficacy. [ABSTRACT FROM AUTHOR]

A Systematic Review of Adenosine in AF Ablation Introduction Pulmonary vein reconnection is a major limitation of pulmonary vein isolation (PVI) for symptomatic atrial fibrillation (AF). Adenosine may unmask dormant PV conduction and facilitate consolidation of PV isolation. We performed a systematic review of the literature to determine the impact of routine adenosine administration on clinical outcomes in patients undergoing PVI. Methods References and electronic databases reporting AF ablation and adenosine following PVI were searched through to 31 July 2012. Six studies included 544 patients to assess the impact of catheter ablation to target adenosine-induced PV reconnection on AF ablation outcome and 3 studies included 612 patients to assess the impact of adenosine testing on AF ablation outcome. Relative risks were calculated and combined in a meta-analysis using random effects modeling. Results Routine adenosine testing for PV reconnection with additional targeted ablation resulted in a significant increase in freedom from AF post-PVI (RR 1.25; 95% CI 1.12-1.40; P < 0.001). However, within the group of patients undergoing adenosine testing, those with reconnection identified a population with a trend to reduction in freedom from AF despite the use of further targeted ablation in the reconnection group (RR 0.91 with 95% CI 0.81-1.03; P = 0.15). Conclusion Routine adenosine testing is associated with an improvement in freedom from AF post-PVI. Paradoxically acute adenosine-induced PV reconnection may portend a greater likelihood of AF recurrence despite additional ablation. Randomized controlled trials are required to determine the role of adenosine testing post-PVI. [ABSTRACT FROM AUTHOR]

Left Septal Atrial Tachycardias. Objective: The objective was to characterize the electrocardiographic and electrophysiological features of focal atrial tachycardia (FAT) originating from the left septum (LS). Background: FAT is recognized to occur at predefined anatomic locations rather than randomly throughout the atria. We describe the ECG and EP features of ATs originating from the LS as an important site for apparent perinodal tachycardias. Methods: Nine patients presenting with LS FAT from a consecutive series of 384 underwent EP/RFA for symptomatic FAT. Results: The mean age was 56 ± 12 years; 7 female with symptoms for 36 ± 28 months. P wave morphology (PWM) was negative/positive in lead V1 and across the precordial leads and negative or negative/positive in inferior leads in all patients. Tachycardia was incessant in 6 out of 9 patients with a mean tachycardia cycle length 421 ± 56 milliseconds. His A was ahead of P wave in all patients (mean −15 ± 5 milliseconds) and earlier than CS proximal (mean 4 ± 9 milliseconds). Successful acute focal ablation achieved at a mean of 31 ± 12 milliseconds ahead of P wave with no recurrences at a mean follow-up of 30 ± 28 months. Conclusion: Although the left septum is an uncommon site for focal AT an awareness of this location for harboring foci is particularly important when mapping apparently right-sided septal tachycardias. (J Cardiovasc Electrophysiol, Vol. 24, pp. 413-418, April 2013) [ABSTRACT FROM AUTHOR]

Atrial Remodeling in Atrial Flutter. Introduction: Atrial fibrillation (AF) and atrial flutter (AFL) are related arrhythmias with common triggers, yet in individual patients either AF or AFL often predominates. We performed detailed electrophysiologic (EP) and electroanatomic (EA) studies of the right atrium (RA) in patients with AF and AFL to determine substrate differences that may explain the preferential expression of AF/AFL in individual patients. Methods: Patients with AF (n = 13) were compared to patients with persistent AFL (n = 10). Detailed studies were performed, and 3-dimensional electroanatomic mapping studies were created and the RA was divided into 4 segments for regional analysis. Global, septal, lateral, anterior, and posterior segments were compared for analysis of: bipolar voltage; proportion of low-voltage areas and areas of electrical silence; conduction times; and proportion of abnormal signals (fractionated signals and double potentials). Results: Compared to patients with AF, patients with AFL had (1) lower bipolar voltage and an increase in the proportion of low-voltage areas; (2) an increase in the proportion of complex signals; and (3) prolongation of activation times. Conclusions: Patients with AFL showed more advanced remodeling than patients with AF with slowed conduction, lower voltage areas with regions of electrical silence, and a greater proportion of complex signals, particularly in the posterior RA. These changes facilitate the stabilization of AFL and may explain why some patients are more likely to develop AFL as a sustained clinical arrhythmia. (J Cardiovasc Electrophysiol, Vol. 23 pp. 1067-1072, October 2012) [ABSTRACT FROM AUTHOR]

Abstract: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in human beating hearts. AF initiates self-perpetuating changes in electrophysiology, structure and functional properties of the atria, a phenomenon known as atrial remodeling. Hypertension, heart failure, valvular heart disease, sleep apnea, congenital heart disease are well known risk factors for AF that contribute to the development of atrial substrate. There is some evidence that reversal of atrial remodeling is possible with correction of antecedent conditions, however the timing of the intervention or upstream therapy may be critical. This review will describe the pathophysiology of atrial remodeling as it pertains to AF. We will describe components of remodeling including changes in atrial refractoriness, conduction and atrial structure, in addition to autonomic changes and anatomic factors that predispose to remodeling. We will discuss our current understanding of the electrophysiological changes that contribute to AF persistence. We will describe nature of atrial and pulmonary vein remodeling in the context of different forms of AF, with and without predisposing risk factors. We will describe the nature of remodeling over time following therapeutic interventions such as AF ablation in order to show that it does not necessarily improve and may worsen. [Copyright &y& Elsevier]

Atrial Remodeling in Atrial Fibrillation. Introduction: The nature of the atrial substrate thought to contribute toward maintaining atrial fibrillation (AF) outside the pulmonary veins remains poorly defined. Therefore, our objective was to determine whether patients with paroxysmal and persistent AF have an abnormal electroanatomic substrate within the left atrium (LA). Methods and Results: Thirty-one patients with AF (17 paroxysmal AF and 14 persistent AF) were compared with 15 age-matched controls with left-sided supraventricular tachycardia (SVT). High-density 3-dimensional electroanatomic maps were created and the LA was divided into 8 segments for regional analysis. Bipolar voltage, conduction, and effective refractory periods (ERPs) of the posterior LA, left atrial appendage (LAA), and distal coronary sinus (CSd) and percentage complex signals were assessed. In the majority of LA regions, compared with controls, AF patients had: (1) lower mean voltage and a higher percentage low voltage; (2) slower conduction; and (3) more prevalent complex signals. Many of these changes were more marked in the persistent than the paroxysmal AF group. Conclusions: Patients with AF have lower regional voltage, increased proportion of low voltage, slowed conduction, and increased proportion of complex signals compared to controls. Many of these changes are more pronounced in persistent AF patients, suggesting there may be a progressive nature to the changes. Differences occurred in the absence of structural heart disease. These substrate abnormalities provide further insight into the progressive nature of atrial remodeling and the mechanisms involved in maintenance of AF. (J Cardiovasc Electrophysiol, Vol. 23 p. 232-238, March 2012.) [ABSTRACT FROM AUTHOR]

Electroanatomic Properties of the Pulmonary Veins. Introduction: Rapid PV activity is critical in initiating and maintaining AF. The underlying substrate responsible for this remains uncertain. We sought to identify if patients with paroxysmal (PAF) and persistent atrial fibrillation (PeAF) have an abnormal substrate within the pulmonary veins (PVs). Methods and Results: Thirty-nine patients with AF (21 PAF, 18 PeAF) were compared with 15 age-matched controls with left-sided accessory pathways (AVRT). High-density 3D electroanatomic maps of the PVs were created. PV voltage, conduction, PV muscle sleeve length, effective refractory periods (ERPs) of the PVs, posterior left atrium (PLA), left atrial appendage (LAA) and distal coronary sinus (CSd), and signal complexity were assessed. Compared with controls, the PVs of AF patients had (1) lower mean-voltage and a higher % low-voltage; (2) shorter PV muscle sleeves; (3) slower conduction; (4) shorter ERP; and (5) more prevalent complex signals. Compared with the PAF group, the PeAF group had (1) higher % low voltage; (2) slower conduction; and (3) more complex signals. In PAF patients, the PLA and LAA ERPs were longer than controls and the PV ERP was shorter than controls; in PeAF patients PLA and LAA ERPs were reduced, but to a lesser extent than in the PVs. AF induction occurred during PV ERP testing in both AF groups, but not controls. Conclusions: PAF and PeAF patients demonstrate electrical and electroanatomic remodeling of the PVs compared to control patients without prior AF. Some of these changes were more marked in PeAF. (J Cardiovasc Electrophysiol, Vol. 22, pp. 1083-1091, October 2011) [ABSTRACT FROM AUTHOR]

Background: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common mechanism of supraventricular tachycardia. Slow pathway (SP) ablation is the first-line treatment approach with a high acute success rate and a low risk of inadvertent complete atrioventricular (AV) block. However, there is still some uncertainty as to the most appropriate procedural endpoints and the impact of these on risk of recurrence. We report the acute and long-term results of SP ablation in a large single-center consecutive series and analyze predictors of acute success and late recurrence. Methods: The study included 1,448 consecutive procedures in 1,419 patients with AVNRT (mean age 49 ± 17 years, 66% women) who underwent SP ablation using a combined electrophysiologic and anatomic approach. Univariate and multivariate analysis was performed for potential predictors of acute success and late recurrence. Results: Acute success was achieved in 98.1%. Transient (first, second, or third degree) AV block occurred during the procedure in 20 (1.41%) patients. One patient (0.07%) had persistent first-degree and transient second-degree AV block after ablation and underwent pacemaker implant at day 21. Of the 1,391 patients with successful ablation, 22 patients (1.5%) developed AVNRT recurrence during a follow-up period of 63 ± 38 months. The only independent predictor of reduced procedural success was the presence of atypical AVNRT (hazard ratio 3.1, P = 0.04). Independent predictors of AVNRT recurrence were age <20 years and female gender (hazard ratios 14.1 and 3.7, respectively). No significant difference in the incidence of late recurrence was observed in patients with or without residual slow-pathway conduction, or according to use of isoproterenol testing or general anesthesia. However, patients with a single echo with recurrence had a significantly larger echo window (median 85 ms) than those without (median 30 ms, P = 0.01). Conclusions: This study demonstrates in a large consecutive single-center series that SP ablation using radiofrequency energy is a highly effective procedure with an extremely low risk of inadvertent AV block and a low recurrence rate. We found that single-AV nodal echo beats represented a procedural endpoint that did not predict AVNRT recurrence but that a large echo window is associated with recurrence. Recurrence rates in this series were higher in young women, possibly reflecting a more conservative approach to ablation in this age group. (PACE 2011; 34:927-933) [ABSTRACT FROM AUTHOR]

In patients with surgical atrial septal defect (ASD) repair, late atrial flutters (AFLs), including cavotricuspid isthmus (CTI)-dependent and non-CTI-dependent scar-related flutter (AFL), are common. Radiofrequency ablation (RFA) of these arrhythmias has a high acute success rate. We aimed to characterize the long-term freedom from atrial arrhythmias in this population. Twenty consecutive patients undergoing RFA for AFL late after ASD repair were included. Electrophysiological assessment included multipolar activation, entrainment, and electroanatomic mapping. Clinical, electrocardiograph, and Holter monitoring follow-up was conducted every 6 months. Mean age was 53 ± 13 years. Time from surgical repair to RFA was 29 ± 15 years. All patients had CTI-dependent AFL (20/20). There were 1.6 ± 0.7 arrhythmias per patient; other arrhythmias included non-CTI-dependent AFL (14), focal atrial tachycardia (two), and atrioventricular nodal reentry tachycardia (two) . Acute success was obtained in 100%. Five patients with recurrent AFL (three CTI dependent, two non-CTI dependent) at 13 ± 8 months had successful repeat RFA. At 3.2 ± 1.6 years follow-up since the last procedure, 90% of patients with successful RFA for AFL remained free of their clinical arrhythmia. However, 30% of the original 20 patients had documented atrial fibrillation (AF) 2.1 ± 1.6 years after the last procedure; five (25%) required AF intervention. One stroke (5%) occurred in the context of late AF. RFA of AFL occurring late after surgical ASD repair has a low long-term risk of recurrence, although 25% of patients required two procedures. However, there is a high late incidence of AF (30%), with an additional 25% of patients requiring intervention for AF. (PACE 2011; 34:431-435) [ABSTRACT FROM AUTHOR]

Atrial Fibrillation and Pulmonary Vein Tachycardia. Objectives: This study aimed to characterize the long-term outcome and incidence of atrial fibrillation (AF) in patients following catheter ablation of focal atrial tachycardia (AT) from the pulmonary veins (PV). Background: Although both AT and AF may originate from ectopic foci within PVs, it is unknown whether PV AT patients subsequently develop AF. Methods: Twenty-eight patients with 29 PV ATs (14%) from a consecutive series of 194 patients who underwent RFA for focal AT were included. Patients with concomitant AF prior to the index procedure were excluded. Results: The minimum follow-up duration was 4 years; mean age 38 ± 18 years with symptoms for 6.5 ± 10 years, having tried 1.5 ± 0.9 antiarrhythmic drugs. The distribution of foci was: left superior 12 (41%), right superior 10 (34%), left inferior 5 (17%), and right inferior 2 (7%). The focus was ostial in 93% and 2–4 cm distally within the vein in 7%. Mean tachycardia cycle length was 364 ± 90 ms. Focal ablation was performed in 25 of 28 patients. There were 6 recurrences with 5 from the original site. Twenty-six patients were available for long-term clinical follow-up. At a mean of 7.2 ± 2.1 years, 25 of 26 (96%) were free from recurrence off antiarrhythmic drugs. No patients developed AF. Conclusions: Focal ablation for tachycardia originating from the PVs is associated with long-term freedom from both AT and AF. Therefore, although PV AT and PV AF share a common anatomic distribution, PV AT is a distinct clinical entity successfully treated with focal RFA and not associated with AF in the long term. (J Cardiovasc Electrophysiol, Vol. pp. 747-750, July 2010) [ABSTRACT FROM AUTHOR]

Ablation of Right Atrial Free Wall Flutter. Introduction: Ablation for atypical atrial flutter (AFL) is often performed during tachycardia, with termination or noninducibility of AFL as the endpoint. Termination alone is, however, an inadequate endpoint for typical AFL ablation, where incomplete isthmus block leads to high recurrence rates. We assessed conduction block across a low lateral right atrial (RA) ablation line (LRA) from free wall scar to the inferior vena cava (IVC) or tricuspid annulus in 11 consecutive patients with atypical RA free wall flutter. Method and results: LRA block was assessed following termination of AFL, by pacing from the ablation catheter in the low lateral RA posterior to the ablation line and recording the sequence and timing of activation anterior to the line with a duodecapole catheter, and vice versa for bidirectional block. LRA block resulted in a high to low activation pattern on the halo and a mean conduction time of 201 ± 48 ms to distal halo. LRA conduction block was present in only 2 out of 6 patients after termination of AFL by ablation. Ablation was performed during sinus rhythm (SR) in 9 patients to achieve LRA conduction block. No recurrence of AFL was observed at long-term follow-up (22 ± 12 months); 3 patients developed AF. Conclusion: Termination of right free wall flutter is often associated with persistent LRA conduction and additional radiofrequency ablation (RFA) in SR is usually required. Low RA pacing may be used to assess LRA conduction block and offers a robust endpoint for atypical RA free wall flutter ablation, which results in a high long-term cure rate. (J Cardiovasc Electrophysiol, Vol. 21, pp. 526-531, May 2010) [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to compare the electrophysiologic substrate in ischemic cardiomyopathy (ICM) patients with and without sustained monomorphic ventricular tachycardia (SMVT). Background: Despite the universal presence of potentially arrhythmogenic left ventricular (LV) scarring, it is not clear why the majority of ICM patients never develop SMVT. Methods: Detailed electroanatomic mapping of the LV endocardium was performed in 17 stable control ICM patients (16 males) without clinical SMVT. They were compared with 17 ICM patients (15 males) with spontaneous SMVT. Standard definitions of low-voltage zones and fractionated, isolated, and very late potentials were used. Results: There were no significant baseline differences between the groups in terms of LV diameter, ejection fraction (27% vs. 28%), infarct territory, or time from infarction. However, control patients had smaller total low-voltage area ≤1.5 mv (30% of surface area vs. 55%, p < 0.001); smaller very low-voltage area <0.5 mv (7.3% vs. 29%, p < 0.001); higher mean voltage of low-voltage zones; fewer fractionated, isolated, and very late potentials with lower density of these scar-related electrograms per unit low-voltage area; and less SMVT inducibility. Potential conducting channels within dense scar and adjacent to the mitral annulus were more frequent in SMVT patients. Conclusions: Compared with ICM patients with SMVT, an otherwise similar control group demonstrated markedly smaller endocardial low-voltage zones, lower scar-related electrogram density, and fewer conducting channels with faster conduction velocity. These findings may explain why some ICM patients develop SMVT and others do not. [Copyright &y& Elsevier]