Junctional Tachycardia: A Critical Reassessment.

Junctional tachycardia (JT) is typically considered to have an automatic mechanism originating from the distal atrioventricular node. When there is 1:1 retrograde conduction via the fast pathway, JT would resemble the typical form of atrioventricular nodal re-entrant tachycardia (AVNRT). Atrial pacing maneuvers have been proposed to exclude AVNRT and suggest a diagnosis of JT. However, after excluding AVNRT, one should consider the possibility of an infra-atrial narrow QRS re-entrant tachycardia, which can exhibit features that resemble AVNRT as well as JT. Pacing maneuvers and mapping techniques should be performed to assess for infra-atrial re-entrant tachycardia before concluding that JT is the mechanism of a narrow QRS tachycardia. Distinguishing JT from typical AVNRT or infra-atrial re-entrant tachycardia has notable implications regarding the approach to ablation of the tachycardia. Ultimately, a contemporary review of the evidence on JT raises some questions as to the mechanism and source of what has traditionally been considered JT.

The utility of a novel mapping algorithm utilizing vectors and global pattern of propagation for scar-related atrial tachycardias.

BACKGROUND: Activation maps of scar-related atrial tachycardias (AT) can be challenging to interpret due to difficulty in inaccurate annotation of electrograms, and an arbitrarily predefined mapping window. A novel mapping software integrating vector data and applying an algorithmic solution taking into consideration global activation pattern has been recently described (Coherent™, Biosense Webster "Investigational"). OBJECTIVE: We aimed to assess the investigational algorithm to determine the mechanism of AT compared with the standard algorithm. METHODS: This study included patients who underwent ablation of scar-related AT using the Carto 3 and the standard activation algorithm. The mapping data were analyzed retrospectively using the investigational algorithm, and the mechanisms were evaluated by two independent electrophysiologists. RESULTS: A total of 77 scar-related AT activation maps were analyzed (89.6% left atrium, median tachycardia cycle length of 273 ms). Of those, 67 cases with a confirmed mechanism of arrhythmia were used to compare the activation software. The actual mechanism of the arrhythmia was more likely to be identified with the investigational algorithm (67.2% vs. 44.8%, p = .009). In five patients with dual-loop circuits, 3/5 (60%) were correctly identified by the investigational algorithm compared to 0/5 (0%) with the standard software. The reduced atrial voltage was prone to lead to less capable identification of mechanism (p for trend: .05). The investigational algorithm showed higher inter-reviewer agreement (Cohen's kappa .62 vs. .47). CONCLUSIONS: In patients with scar-related ATs, activation mapping algorithms integrating vector data and "best-fit" propagation solution may help in identifying the mechanism and the successful site of termination.

Recurrent Atrial Fibrillation After Initial Long-Term Ablation Success: Electrophysiological Findings and Outcomes of Repeat Ablation Procedures.

BACKGROUND: Atrial fibrillation recurrence after initial long-term success of catheter ablation has been described, yet not well studied. We assessed the electrophysiological findings and outcomes of repeat ablation procedures in this setting. METHODS AND RESULTS: Between 2000 and 2015, 10 378 patients underwent atrial fibrillation ablation and were enrolled in a prospectively maintained data registry. From this registry, we included all 137 consecutive patients who had initial long-term success, defined as freedom from recurrent arrhythmia for >36 months off antiarrhythmics, then underwent repeat ablation for recurrent atrial fibrillation. The median arrhythmia-free period that defined long-term success was 52 months (41-68 months). In redo ablations, reconnection along at least one of the pulmonary veins (PVs) was found in 111 (81%) patients. Reconnection along a left superior, left inferior, right superior, and right inferior PV was found in 64%, 62%, 50%, and 54% of patients, respectively, and were reisolated. Additional non-PV ablations were performed in 127 (92.7%) patients: posterior wall (46%), septal to right PVs (49%), superior vena cava (35%), roof lines (52%), and cavotricuspid isthmus (33%). After a median follow-up of 17 months (5-36.9 months), 103 patients (75%) were arrhythmia free (79 off antiarrhythmics, 24 on antiarrhythmics). CONCLUSIONS: PV reconnection is the most common electrophysiological finding in patients with atrial fibrillation recurrence after long-term success, but with lower rates than what had been reported for early recurrences. In our experience, repeat ablations in this setting involve complex ablation approaches to reisolate the PVs and modify the atrial substrate and are associated with good success rates.

Randomized Study of Persistent Atrial Fibrillation Ablation: Ablate in Sinus Rhythm Versus Ablate Complex-Fractionated Atrial Electrograms in Atrial Fibrillation.

BACKGROUND: Achieving long-term successful outcomes with ablation of persistent atrial fibrillation (AF) remains a clinical and procedural challenge. We aimed to assess 2 ablation strategies for persistent AF: pulmonary vein antral isolation (PVAI) in sinus rhythm after direct current cardioversion versus PVAI and ablation targeting complex-fractionated atrial electrograms while in AF. METHODS AND RESULTS: Between June 2009 and July 2013, patients with continuous persistent AF for ≥3 months were prospectively randomized to either direct current cardioversion before PVAI and posterior wall/septum ablation while in sinus rhythm (group 1), versus same ablation in group 1 in addition to complex-fractionated atrial electrogram ablation while in AF (group 2). The procedural profiles and clinical outcomes of the 2 strategies were compared. Ninety patients were randomized to group 1 (n=46) or group 2 (n=44). There were no differences in baseline characteristics between groups. Over 365 days of follow-up after the index procedure, 16 patients (35%) in group 1 and 13 patients (30%) in group 2 remained arrhythmia-free off antiarrhythmic medications. Over long-term follow-up (median, 867 days), arrhythmia-free survival off antiarrhythmic medications was more likely in group 1 than in group 2 in Kaplan-Meier analysis (Log Rank P=0.04). Group 1 ablation was associated with significantly shorter procedural duration and fluoroscopy time (231±72 versus 273±76 min; P=0.008 and 54 [Q1-Q3: 46-67] versus 66 (Q1-Q3: 53-83] min; P=0.018, respectively). CONCLUSIONS: In patients with persistent AF, PVAI in sinus rhythm after direct current cardioversion is associated with higher success and shorter procedural and fluoroscopy times compared with PVAI in AF with additional complex-fractionated atrial electrogram ablation. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02429648.

Evolving strategies to prevent stroke and thromboembolism in nonvalvular atrial fibrillation.

Stroke prevention in patients with nonvalvular atrial fibrillation relies on an assessment of the individual risks for stroke and bleeding. Patients at high risk for stroke are candidates for anticoagulant therapy. Anticoagulants, however, have substantial bleeding risks that must be weighed in the therapeutic decision. Warfarin has been the traditional choice, but the recently introduced novel oral anticoagulants offer similar efficacy with less bleeding risk. Additionally, they do not require monitoring and have fewer drug interactions and dietary restrictions than warfarin. Several devices, which isolate the left atrial appendage, have become available as treatment options for patients with elevated risks of both thromboembolism and bleeding complications.

Characteristics, treatment, and outcomes of periprocedural cerebrovascular accidents during electrophysiologic procedures.

OBJECTIVES: We sought to identify the characteristics, treatment, and outcomes of periprocedural cerebrovascular accident (PCVA) during electrophysiologic (EP) procedures. BACKGROUND: Periprocedural cerebrovascular accident is one of the most feared complications during EP procedures with very few data regarding its characteristics, management, and outcomes. METHODS: Between January 1998 and December 2008, we reviewed 30,032 invasive EP procedures for PCVA occurrence and characteristics. Management and outcomes were also determined. RESULTS: Thirty-eight CVAs were identified. Twenty (53 %) were intraprocedural and 18 (47 %) postprocedural. Thirty-two (84 %) were classified as strokes and six (16 %) as transient ischemic attacks. All CVAs except one (37, 97 %) were ischemic and the vast majority occurred during ablation procedures (36, 95 %). Among the 31 patients with ischemic stroke, 11 (35 %) were treated with reperfusion (eight catheter-based therapy and three intravenous t-PA) of whom five (46 %) had complete recovery, three (27 %) had partial recovery, and three (27 %) had no recovery. No hemorrhagic transformations occurred. CONCLUSION: Periprocedural cerebrovascular accident during EP procedures is rare and is almost always ischemic. It occurs more frequently during ablation procedures. Reperfusion therapy is feasible and safe.

A distinct family of acetylcholinesterases is secreted by Nippostrongylus brasiliensis.

A third variant of acetylcholinesterase (AChE A) secreted by the parasitic nematode Nippostrongylus brasiliensis has been isolated which shows 63-64% identity to AChE B and AChE C, with a truncated carboxyl terminus and a short internal insertion relative to AChEs from other species. Three of the fourteen aromatic residues which line the active site gorge in Torpedo AChE are substituted by non-aromatic residues (Y70T, W279D and F288M). All three enzymes have 8 cysteine residues in conserved positions, including 6 which have been implicated in disulphide bonds in other AChEs. Phylogenetic analysis suggests that these enzymes form a distinct group which evolved after speciation and are most closely related to ACE-2 of Caenorhabditis elegans. Recombinant AChE A secreted by Pichia pastoris was monomeric and hydrophilic, with a substrate preference for acetylthiocholine and negligible activity against butyrylthiocholine. A model structure of AChE A built from the coordinates of the Torpedo californica AChE suggests that W345 (F331 in Torpedo) limits the docking of butyrylcholine. This model is consistent with mutational analysis of the nematode enzymes. Expression of AChE A is regulated at the transcriptional level independently of the other 2 secreted variants, with maximal expression by fourth stage larvae and young adult worms. These enzymes thus appear to represent an unusual family of AChEs with conserved structural features which operate outside the normal boundaries of known functions in regulation of endogenous neurotransmitter activity.