An improved window of interest for electroanatomical mapping of atrial tachycardia.

PURPOSE: Diagnosis of atrial tachycardia (AT) with 3D mapping system remains challenging due to fibrosis or previous ablation. This study aims to evaluate a new electroanatomical mapping annotation setting using a window of interest adjusted at the end of the P wave (WOIp wave) to identify the AT mechanism more accurately. METHODS: Twenty patients with successful ablation of left AT using navigation system CARTO3 were evaluated. Two maps for each patient were generated offline using either conventional settings of WOI (WOIconv.) or WOIp wave. Three investigators from two centres analysed the maps blindly. RESULTS: Mechanisms of AT were macroreentrant in 14/20 patients (70%) and focal in 6/20 (30%). WOIp wave resulted in a significant increase in the percentage of correct identification of the mechanism based on mapping alone (93.3 ± 13.7% vs 58.3 ± 33.9%; p = 0.0003) compared with WOIconv.. Diagnoses based on mapping were arrived at faster (27.8 ± 16.4 s vs 38.97 ± 13.64 s, respectively; p = 0.0231) and with a greater confidence in the diagnosis (confidence index 2.57 ± 0.45 vs 2.12 ± 0.45, respectively; p = 0.0024). With perimitral re-entry specifically "early meets late" was closer to the anatomical region of the mitral isthmus (15.9 ± 20.9 mm vs 48.77 ± 23.23 mm, respectively; p = 0.0028). CONCLUSIONS: This study found that electroanatomical mapping acquisition with a window of interest set at the end of the P wave improves the ability to diagnose the arrhythmia mechanism based on the initial map. It is particularly beneficial in identifying area of interest for ablation in perimitral AT.

High-Power (40-50 W) Radiofrequency Ablation Guided by Unipolar Signal Modification for Pulmonary Vein Isolation: Experimental Findings and Clinical Results.

Background Although proposed to facilitate pulmonary vein isolation (PVI), high-power ablation may favor extracardiac damage. Negative component abolition of the unipolar signal reflects lesion transmurality. The present study sought to evaluate the safety and efficacy of high-power ablation using unipolar signal modification as a local end point. Methods High power and standard power were compared in 4 swine and 100 consecutive patients referred for PVI. The first 50 patients were included in the control group (25-30 W) and the last 50 patients in the study group (40-50 W). Atrial radiofrequency applications were stopped 2 s (study group and swine) or 5 s (control group) after unipolar signal modification. Ventricular radiofrequency applications of 500 J (25 W·20 s versus 50 W·10 s) were performed at the swine epicardium. Results Swine gross necropsy did not show any extracardiac damage related to atrial lesions. At equal energy of 500 J, 50 W lesions were deeper (3±0.9 versus 2.6±1.1 mm; P=0.03) and wider (6.2±2 versus 5±2.3 mm; P=0.006) than 25 W lesions. No complications occurred during the clinical study, whatever the power output used for PVI. For a similar sinus rhythm maintenance at 12 months (90% versus 88%; P=0.75), the study group displayed higher first-pass PVI (92% versus 73%; P<0.001), lower acute pulmonary vein reconnection (2% versus 17%; P<0.001), reduced procedure time (73.1±18.2 versus 107.4±21.2 min; P<0.001), and ablation time (13±2.9 versus 30.3±8.8 min; P<0.001). Conclusions High-power PVI guided by unipolar signal modification safely decreases procedural burden while ensuring robust 12-month outcomes.

Elimination of the negative component of the unipolar electrogram as a local procedural endpoint during paroxysmal atrial fibrillation catheter ablation using contact-force sensing: the UNIFORCE study.

PURPOSE: Elimination of the negative component of the unipolar atrial electrogram is a reliable indicator of the creation of a transmural lesion. Contact-force (CF) sensing technology has the potential to increase the durability of pulmonary vein isolation (PVI). In the present multicenter study, we assessed the 2-year sinus rhythm (SR) maintenance rate in patients with paroxysmal atrial fibrillation (PAF) after PVI guided by these two approaches. METHODS: Two hundred fifteen consecutive PAF patients (62.1 ± 10.1 years, 65 women) were prospectively enrolled. All patients underwent PVI under CARTO guidance according to a systematic contiguous "point-by-point" approach, using radiofrequency energy, and a CF externally irrigated ablation catheter with the goal of at least 10g (ideally 20g) of force. The ablation endpoint of each individual lesion was elimination of the negative component of the unipolar atrial signal. The procedural endpoint was PVI with bidirectional block. RESULTS: All PVs were successfully isolated. After 30 min of waiting time, 35 patients (16%) had PV reconnection and in all of them, the PVs were re-isolated. Two years after a single ablation procedure, 187 patients (87%) remained arrhythmia free, without anti-arrhythmic drugs. Of the 28 patients presenting with AF recurrence, 25 had PV reconnection and underwent repeat PVI while in the remaining 3 patients, all four PVs were isolated and extra-PV triggers were identified. There were six groin hematomas and one transient ischemic attack. CONCLUSIONS: Unipolar atrial signal analysis combined with CF sensing ensures a robust 2-year SR maintenance rate in the treatment of PAF. Clinical trial registration-URL: http://www.clinicaltrials.gov . Unique identifier: NCT02520960.

The Latent Structure of Dictionaries.

How many words-and which ones-are sufficient to define all other words? When dictionaries are analyzed as directed graphs with links from defining words to defined words, they reveal a latent structure. Recursively removing all words that are reachable by definition but that do not define any further words reduces the dictionary to a Kernel of about 10% of its size. This is still not the smallest number of words that can define all the rest. About 75% of the Kernel turns out to be its Core, a "Strongly Connected Subset" of words with a definitional path to and from any pair of its words and no word's definition depending on a word outside the set. But the Core cannot define all the rest of the dictionary. The 25% of the Kernel surrounding the Core consists of small strongly connected subsets of words: the Satellites. The size of the smallest set of words that can define all the rest-the graph's "minimum feedback vertex set" or MinSet-is about 1% of the dictionary, about 15% of the Kernel, and part-Core/part-Satellite. But every dictionary has a huge number of MinSets. The Core words are learned earlier, more frequent, and less concrete than the Satellites, which are in turn learned earlier, more frequent, but more concrete than the rest of the Dictionary. In principle, only one MinSet's words would need to be grounded through the sensorimotor capacity to recognize and categorize their referents. In a dual-code sensorimotor/symbolic model of the mental lexicon, the symbolic code could do all the rest through recombinatory definition.