Functional allele of a MATE gene selected during domestication modulates seed color in chickpea.

Seed color is one of the key target traits of domestication and artificial selection in chickpeas due to its implications on consumer preference and market value. The complex seed color trait has been well dissected in several crop species; however, the genetic mechanism underlying seed color variation in chickpea remains poorly understood. Here, we employed an integrated genomics strategy involving QTL mapping, high-density mapping, map-based cloning, association analysis, and molecular haplotyping in an inter-specific RIL mapping population, association panel, wild accessions, and introgression lines (ILs) of Cicer gene pool. This delineated a MATE gene, CaMATE23, encoding a Transparent Testa (TT) and its natural allele (8-bp insertion) and haplotype underlying a major QTL governing seed color on chickpea chromosome 4. Signatures of selective sweep and a strong purifying selection reflected that CaMATE23, especially its 8-bp insertion natural allelic variant, underwent selection during chickpea domestication. Functional investigations revealed that the 8-bp insertion containing the third cis-regulatory RY-motif element in the CaMATE23 promoter is critical for enhanced binding of CaFUSCA3 transcription factor, a key regulator of seed development and flavonoid biosynthesis, thereby affecting CaMATE23 expression and proanthocyanidin (PA) accumulation in the seed coat to impart varied seed color in chickpea. Consequently, overexpression of CaMATE23 in Arabidopsis tt12 mutant partially restored the seed color phenotype to brown pigmentation, ascertaining its functional role in PA accumulation in the seed coat. These findings shed new light on the seed color regulation and evolutionary history, and highlight the transcriptional regulation of CaMATE23 by CaFUSCA3 in modulating seed color in chickpea. The functionally relevant InDel variation, natural allele, and haplotype from CaMATE23 are vital for translational genomic research, including marker-assisted breeding, for developing chickpea cultivars with desirable seed color that appeal to consumers and meet global market demand.

Association between high-density mapping of atypical atrial flutter, clinical outcomes and healthcare utilization.

BACKGROUND: Success of atypical atrial flutter (AAFL) ablation has historically been limited by difficulty mapping the complex re-entrant circuits involved. While high-density (HD) mapping has become commonplace in clinical practice, there are limited data on outcomes of HD versus non-HD mapping for AAFL ablation. OBJECTIVE: To compare clinical outcomes and healthcare utilization using HD mapping versus non-HD mapping for AAFL ablation. METHODS: Retrospective analysis of all AAFL procedures between 2005 and 2022 at an academic medical center was conducted. Procedures utilizing a 16-electrode HD Grid catheter and Precision mapping system were compared to procedures using prior generation 10-20 electrode spiral catheters and the Velocity system (Abbott, IL). Cox regression models and Poisson regression models were utilized to examine procedural and healthcare utilization outcomes. Models were adjusted for left ventricular ejection fraction, CHA2DS2-VASc, and history of prior ablation. RESULTS: There were 108 patients (62% HD mapping) included in the analysis. Baseline clinical characteristics were similar between groups. Use of HD mapping was associated with a higher rate of AAFL circuit delineation (92.5% vs. 76%; p = .014) and a greater adjusted procedure success rate, defined as non-inducibility at procedure end, (aRR (95% CI) 1.26 (1.02-1.55) p = .035) than non-HD mapping. HD mapping was also associated with a lower rate of ED visits (aIRR (95% CI) 0.32 (0.14-0.71); p = .007) and hospitalizations (aIRR (95% CI) 0.32 (0.14-0.68); p = .004) for AF/AFL/HF through 1 year. While there was a lower rate of recurrent AFL through 1 year among HD mapping cases (aHR (95% CI) 0.60 (0.31-1.16) p = .13), statistical significance was not met likely due to the low sample size and higher rate of ambulatory rhythm monitoring in the HD group (61% vs. 39%, p = .025). CONCLUSION: Compared to non-HD mapping, AAFL ablation with HD mapping is associated with improvements in the ability to define the AAFL circuit, greater procedural success, and a reduction in the number of ED visits and hospitalization for AF/AFL/HF.

Automatic identification of ablation targets in persistent atrial fibrillation: Initial experience with a new mapping tool.

INTRODUCTION: Strategies beyond pulmonary vein isolation (PVI) in persistent atrial fibrillation (persAF) are debated. A novel mapping tool provides algorithmic detection of ablation targets based on electrogram (EGM) properties specific to stable localized rotational activations. METHODS: The mapping tool was used on 31 patients (20 de novo). The algorithm was used to optimize PVI line placement and guide additional ablations. Targets were detected by calculating local cycle length (L-CL) and local spread of activation within that L-CL (Duty Cycle; DC) for EGMs with consistent morphology and activation. At least two left atrial (LA) maps (pre-PVI and post-PVI) were acquired in atrial fibrillation (AF) in all patients (except those with AF termination during PVI). Extra-pulmonary vein (PV) targets were compared between the two LA maps in each patient. Follow-up included Holter monitoring every 3 months. RESULTS: Patients had a median of 3 extra-PV drivers/targets. The majority (81%) were localized in the same areas between the two LA maps. All patients had progressive AF organization demonstrated by global activation slowing: histogram peak L-CL increased from 162 to 171 ms (post-PVI; p = .0003) than to 175 ms (posttarget ablation; p = .04). Moreover, L-CL dispersion was reduced by ablation; in 50% their values tended to cluster around two dominant cycles. In de novo patients AF terminated to sinus rhythm or atrial tachycardia (AT) within 48 h postprocedure in 88% of cases, and at 18 months mean follow-up recurrence occurred in only five (25%) patients (three persAF, two AT). There were no complications. CONCLUSION: The algorithmic detection of EGMs consistent with localized reentry during sequential mapping of persAF provided reproducible targets for ablation. This allowed personalized PVI and limited, highly-selective, extra-PV ablation. Results of this initial experience included progressive organization of AF with ablation and a low recurrence rate after a single procedure.

High-density mapping of Koch's triangle during sinus rhythm and typical atrioventricular nodal re-entrant tachycardia, integrated with direct recording of atrio-ventricular node structure potential.

BACKGROUND: The mechanism of typical slow-fast atrioventricular nodal re-entrant tachycardia (AVNRT) and its anatomical and electrophysiological circuit inside the right atrium (RA) and Koch's Triangle (KT) are not well known. OBJECTIVE: To identify the potentials of the compact AV node and inferior extensions and to perform accurate mapping of the RA and KT in sinus rhythm (SR) and during AVNRT, to define the tachycardia circuit. METHODS: Consecutive patients with typical AVNRT were enrolled in 12 Italian centers and underwent mapping and ablation by means of a basket catheter with small electrode spacing for ultrahigh-density mapping and a modified signal-filtering toolset to record the potentials of the AV nodal structures. RESULTS: Forty-five consecutive cases of successful ablation of typical slow-fast AVNRT were included. The mean SR cycle length (CL) was 784.1 ± 6 ms and the mean tachycardia CL was 361.2 ± 54 ms. The AV node potential had a significantly shorter duration and higher amplitude in sinus rhythm than during tachycardia (60 ± 40 ms vs. 160 ± 40 ms, p < .001 and 0.3 ± 0.2 mV vs. 0.09 ± 0.12 mV, p < .001, respectively). The nodal potential duration extension was 169.4 ± 31 ms, resulting in a time-window coverage of 47.6 ± 9%. The recording of AV nodal structure potentials enabled us to obtain 100% coverage of the tachycardia CL during slow-fast AVNRT. CONCLUSION: Detailed recording of the potentials of nodal structures is possible by means of multipolar catheters for ultrahigh-density mapping, allowing 100% of the AVNRT CL to be covered. These results also have clinical implications for the ablation of right-septal and para-septal arrhythmias.

First clinical data on artificial intelligence-guided catheter ablation in long-standing persistent atrial fibrillation.

INTRODUCTION: Despite advanced ablation strategies and major technological improvements, treatment of persistent atrial fibrillation (AF) remains challenging and the underlying pathophysiology is not fully understood. This study analyzed the multiple procedure outcome and safety of catheter ablation of spatiotemporal dispersions (DISPERS) detected by artificial intelligence (AI)-guided software in patients with long-standing persistent AF. METHODS AND RESULTS: The Volta VX1 software was used for 50 consecutive patients undergoing catheter ablation for persistent AF. First, high-density mapping (78% biatrial) with a multipolar mapping catheter was performed. In addition to pulmonary vein isolation (PVI), ablation of DISPERS was performed aiming at homogenizing, dissecting, isolating, or connecting DISPERS areas to nonconducting anatomical structures. Follow-up contained regular visits at our outpatient clinic at 1, 3, 6, and 12 months including 7-day Holter electrocardiograms. Patients were mainly suffering from long-standing persistent AF (mean AF duration 50.30 ± 54.28 months). Following PVI, ablation of left atrial and right atrial DISPERS areas led to AF cycle length prolongation (mean of 162.0 ± 16.6 to 202.2 ± 21.6 ms after) and AF termination to atrial tachycardia (AT) or sinus rhythm (SR) in 12 patients (24%). No stroke or pericardial effusion occurred; major groin complications (pseudoaneurysm n = 1, atrioventricular fistula n = 1) were detected in two patients. After a blanking period of 6 weeks, recurrence of any atrial arrhythmia was documented in 26 patients (52%). The majority of patients presented with organized AT (n = 15) while AF was present in n = 9 patients and AT/AF was observed in n = 2 patients. Twenty-two patients underwent reablation. During a mean follow-up of 363.14 ± 187.42 days and after an average of 1.46 ± 0.68 procedures, 82% of patients remained in stable SR. CONCLUSION: DISPERS-guided ablation using machine learning software (the Volta VX1 software) in addition to PVI in long-standing persistent AF ablation resulted in high long-term success rates regarding AF and AT elimination. Most arrhythmia recurrences were reentrant AT. After a total of 1.46 ± 0.68 procedures, freedom from AF/AT was 82%. Despite prolonged procedure times complication rates were low. Randomized studies are necessary to evaluate long-term efficacy of dispersion-guided ablation using AI.

Contemporary catheter ablation of complex atrial tachycardias after prior atrial fibrillation ablation: pulsed field vs. radiofrequency current energy ablation guided by high-density mapping.

AIMS: Catheter ablation (CA) of post-ablation left atrial tachycardias (LATs) can be challenging. So far, pulsed field ablation (PFA) has not been compared to standard point-by-point radiofrequency current (RFC) energy for LAT ablation. To compare efficacy of PFA vs. RFC in patients undergoing CA for LAT. METHODS AND RESULTS: Consecutive patients undergoing LAT-CA were prospectively enrolled (09/2021-02/2023). After electro-anatomical high-density mapping, ablation with either a pentaspline PFA catheter or RFC was performed. Patients were matched 1:1. Ablation was performed at the assumed critical isthmus site with additional ablation, if necessary. Right atrial tachycardia (RAT) was ablated with RFC. Acute and chronic success were assessed. Fifty-six patients (n = 28 each group, age 70 ± 9 years, 75% male) were enrolled.A total of 77 AT (n = 67 LAT, n = 10 RAT; 77% macroreentries) occurred with n = 32 LAT in the PFA group and n = 35 LAT in the RFC group. Of all LAT, 94% (PFA group) vs. 91% (RFC group) successfully terminated to sinus rhythm or another AT during ablation (P = 1.0). Procedure times were shorter (PFA: 121 ± 41 vs. RFC: 190 ± 44 min, P < 0.0001) and fluoroscopy times longer in the PFA group (PFA: 15 ± 9 vs. RFC: 11 ± 6 min, P = 0.04). There were no major complications. After one-year follow-up, estimated arrhythmia free survival was 63% (PFA group) and 87% (RFC group), [hazard ratio 2.91 (95% CI: 1.11-7.65), P = 0.0473]. CONCLUSION: Pulsed field ablation of post-ablation LAT using a pentaspline catheter is feasible, safe, and faster but less effective compared to standard RFC ablation after one year of follow-up. Future catheter designs and optimization of the electrical field may further improve practicability and efficacy of PFA for LAT.

Atrial fibrillation ablation workflow optimization facilitated by high-power short-duration ablation and high-resolution mapping.

AIMS: Pulmonary vein isolation (PVI) for catheter ablation of atrial fibrillation (AF) is a time-demanding procedure. High-power short-duration (HPSD) ablation protocols and high-density mapping catheters have recently been introduced to clinical practice. We investigated the impact of high-density mapping and HPSD ablation protocols on procedural timing, efficacy, and safety by comparing different standardized set-ups. METHODS AND RESULTS: Three electrophysiology (EP) laboratory set-ups were analysed: (i) circular catheter for mapping and HPSD ablation with 30/35 W guided by an ablation index (AI); (ii) pentaspline catheter for mapping an HPSD ablation with 50 W guided by an AI; and (iii) pentaspline catheter for mapping and HPSD ablation with 90 W over 4 s using a novel ablation catheter. All patients underwent PVI without additional left atrial ablation strategies. Procedural data and operating intervals in the EP laboratory were systematically analysed. Three hundred seven patients were analysed (30/35 W AI: n = 102, 50 W AI: n = 102, 90 W/4 s: n = 103). Skin-to-skin times [105.3 ± 22.7 (30/35 W AI) vs. 81.4 ± 21.3 (50 W AI) vs. 69.5 ± 12.2 (90 W/4 s) min, P ≤ 0.001] and total laboratory times (132.8 ± 42.1 vs. 107.4 ± 25.7 vs. 95.2 ± 14.0 min, P < 0.001) significantly differed among the study groups. Laboratory interval analysis revealed significant shortening of mapping and ablation times. Arrhythmia-free survival after 12 months was not different among the study groups (log-rank P = 0.96). CONCLUSION: The integration of high-density mapping and HPSD protocols into an institutional AF ablation process resulted in reduced procedure times without compromising safety or efficacy.

Conduction velocity mapping in atrial fibrillation using omnipolar technology.

BACKGROUND: Recent studies have shown that atrial slow conduction velocity (CV) is associated with the perpetuation of atrial fibrillation (AF). However, the criteria of CV measurement have not been standardized. The aim of this study was to evaluate the relationship between the slow CV area (SCVA) measured by novel omnipolar technology (OT) and AF recurrence. METHODS: This study included 90 patients with AF who underwent initial pulmonary vein isolation (PVI). The segmented surface area of the SCVA was measured by left atrial (LA) electrophysiological mapping using OT before the PVI. The proportion of the SCVA at each cutoff value of CV (from < 0.6 to < 0.9 m/s) was compared between the patients with and without AF recurrence. RESULTS: During a mean follow-up period of 516 ± 197 days, the recurrence of AF after the initial PVI was observed in 23 (25.5%) patients. In patients with AF recurrence, the proportion of the SCVA in the LA posterior, LA appendage (LAA), and LA anterior were significantly higher than those without AF recurrence. The multivariate analysis indicated that the proportion of the low voltage area and the SCVA in the LA anterior (local CV < 0.7 m/s) were independent predictors of AF recurrence (hazard ratio [HR], 1.07; 95% confidence interval [CI], 1.01-1.14; p = 0.03; HR, 1.40; 95% CI, 1.07-1.83; p = 0.01, respectively). CONCLUSION: By evaluating the local CV using OT, it was indicated that SCVA with CV < 0.7 m/s in the LA anterior is strongly associated with AF recurrence after PVI.

Relationships between biatrial substrate and recurrence after radiofrequency ablation in patients with persistent atrial fibrillation.

BACKGROUND: Global longitudinal strain (GLS) and atrial voltage are acknowledged markers for worse rhythm outcome after ablation of persistent atrial fibrillation (PeAF). The majority of research efforts have been directed towards the left atrium (LA), with relatively fewer studies focusing on the right atrium (RA). The aim of this study was to investigate the effect of the biatrial substrate on the outcome following radiofrequency catheter ablation (RFCA). METHODS: All patients underwent two-dimensional speckle tracking echocardiography (2D-STE) and high-density mapping (HDM) on LA and RA in preoperative and postoperative stages of RFCA. Atrial substrate was assessed by GLS, average voltage, and low voltage zone (LVZ). RESULTS: This retrospective study enrolled 48 patients. With a follow-up of 385.98 ± 161.78 days, 22.92% (11/48) of all patients had AF recurrence and 63.64% in low strain group. Left atrial-low voltage zone (LA-LVZ) prior to RFCA was 67.52 ± 15.27% and 54.21 ± 20.07%, respectively, in the recurrence group and non-recurrence group. Multivariate regression analysis showed that preoperative LA-GLS (OR 0.047, 95%CI 0.002-0.941, p = .046) was independent predictors of AF recurrence. Biatrial average voltage in preoperative and postoperative stages were positively correlated (preoperative: r = 0.563 p < .001; postoperative: r = 0.464 p = .002). There was no significant difference in the proportion of RA in the recurrence group except the septum in preoperative and postoperative stages. CONCLUSIONS: Low LA-GLS and high LA-LVZ may be predictors of RFCA recurrence in PeAF patients. Biatrial average voltage were positively correlated in preoperative and postoperative stages.

Real-time Ripple technique: A case report on Ripple map for real-time identification of conduction gaps without first-pass pulmonary vein isolation.

This paper presents a novel approach to gap mapping in pulmonary vein isolation (PVI) for atrial fibrillation (AF) treatment, utilizing the real-time Ripple (RR) technique. Radiofrequency (RF) catheter ablation, particularly encircling PVI, is a common intervention for AF. Identifying left atrium-pulmonary vein conduction gaps is crucial for achieving PVI with minimal additional ablation if first-pass PVI is unsuccessful. However, identifying conduction gaps can be relatively challenging, often necessitating manual electrocardiogram reannotation due to the limitations of local activation time (LAT) maps. In the case of a 63-year-old patient with drug-resistant symptomatic persistent AF, the RR technique was utilized to identify conduction gaps during RF ablation. The technique involved pausing fast anatomical mapping (FAM), activating Ripple map (RM) feature on the CARTO 3 system and acquiring points with an ultrahigh-resolution mapping catheter. This approach revealed that the actual site of earliest activation differs from the LAT map indication, enabling successful PVI. The RM feature's capability to reflect actual excitation propagation without reliance on map annotations was crucial for precise conduction gap identification, overcoming inter-operator variability and inaccuracies of conventional methods. The RR technique not only facilitated real-time analysis during gap mapping but also significantly reduced the procedure time, minimizing potential complications. This case report highlights the efficacy of the RR technique in real-time gap mapping, demonstrating its value in cases where first-pass PVI is unsuccessful. The integration of this technique into PVI procedures can enhance both the accuracy and efficiency of catheter ablation for AF.

Open window mapping for redo accessory pathway ablation in Ebstein anomaly.

Accessory pathway ablation in Ebstein anomaly can be significantly more challenging than in structurally normal hearts. An alternative to the conventional approach to mapping APs is to detect points with a high-density mapping catheter based on an automated detection algorithm using open window mapping. It detects the sharpest signal at each point with high-density mapping rather than relying on the origin of the local electrogram to localize the pathway and determine a site for successful ablation. We herein report the first case in literature of a redo-accessory pathway ablation in Ebstein anomaly using this technique.

Automatic identification of areas with low-voltage fragmented electrograms for the detection of the critical isthmus of atypical atrial flutters.

INTRODUCTION: Critical isthmuses of atypical atrial flutters (AAFLs) are usually located at slow conduction areas that exhibit fractionated electrograms. We tested a novel software, intended for integration with a commercially available navigation system, that automatically detects fractionated electrograms, to identify the critical isthmus in patients with AAFL ablation. METHODS AND RESULTS: All available patients were analyzed; 27 patients with 33 AAFLs were included. The PentaRay NAV catheter (Biosense Webster) was used for mapping. The novel software was retrospectively applied; fractionated points with duration ≥80 ms and bipolar voltage between 0.05 and 0.5 mV were highlighted on the surface of maps. In 10 randomly chosen AAFLs, an expert electrophysiologist evaluated the positive predictive value of the algorithm to detect true fractionation: 74.4%. We tested the capacity of the software to identify areas of fractionation (defined as clusters of ≥3 adjacent points with fractionation) at the critical isthmus of the AAFLs (defined using conventional mapping criteria). An area of fractionation was identified at the critical isthmus in 30 cases (91%). Globally, 144 areas of fractionation (median number per AAFL 4 [3-6]) were identified. Duration of the fractionation or the surface of the areas was not different between areas at critical isthmuses and the rest. Setting the fractionation score filter of the software in nine provided best performance. CONCLUSIONS: The novel software detected areas of fractionation at the critical isthmus in most AAFLs, which may help identify the critical isthmus in clinical practice.

Optimization of superior vena cava isolation with aid of ablation index guidance.

INTRODUCTION: To investigate the optimal range of quantitative ablation index (AI) value during superior vena cava (SVC) electrical isolation by radiofrequency catheter ablation (RFCA). METHODS: First, in a development cohort of patients with atrial fibrillation (AF), the RFCA with 40 W was performed to complete SVC isolation guided by the conduction breakthrough point from the right atrium to SVC. Then, the range of AI value was calculated by offline analysis on different segments of SVC. Lastly, for the validation of AF patients, the safety and effectiveness of SVC isolation with the optimized target range of AI value were evaluated with an additional adenosine test. RESULTS: A total of 101 patients with AF were included in the study (44 patients in the development cohort/57 in the validation cohort). The segmental ablation strategy was applied in 70% of the patients. According to the offline analysis of the AI values in the development cohort, the target AI value range was set as 350-400. The success rate of SVC isolation in the validation cohort was significantly higher than that in the exploration cohort (100% vs. 90.9%, p = .02), and no complications occurred in the exploration cohort. During the adenosine test, the recovery rate of electrical conduction in SVC was significantly lower than that in the pulmonary vein (3.5% vs. 17.5%). CONCLUSION: The target AI value with a range from 350 to 400 is safe and effective for high-power RFCA to complete SVC isolation.

Impact of Low Voltage Threshold Adjustment on Activation Mapping Interpretation for Atrial Tachycardia in Low-Voltage Left Atrium.

Background: The misinterpretation of activation propagation within low voltage zone (LVZ) can complicate atrial tachycardia (AT) mechanism analysis, especially in patients with remodeled atrial substrate. This study investigated the impact of low voltage threshold adjustment (LVTA) on left atrial (LA) tachycardia activation mapping interpretation. Methods: We identified 55 ATs in 42 patients undergoing catheter ablation for LA tachycardia, with a mean LA voltage of < 0.5 mV. Activation mapping of LA or both atria was used to evaluate AT mechanisms before and after LVTA. Patients underwent regular clinic follow-up after the procedure. Results: Comparing activation mapping before and after LVTA revealed four categories: (1) complete change in AT circuit and ablation design in 9 ATs; (2) an unchanged AT circuit but tailored ablation design in 16 ATs; (3) identification of bystander gaps in 3 ATs; (4) an unchanged AT circuit and ablation design in 27 ATs. Effective ablation, defined as AT termination or circuit change, was obtained in all 9 Type 1 ATs and 15 of 16 Type 2 ATs by targeting the critical area identified by activation mapping after LVTA. After a median follow-up of 16.5 months, the cumulative freedom from AT was 69.3%. Conclusions: In patients with low LA voltage, conduction propagation hidden within LVZ was not uncommon, but is often excluded from activation mapping. LVTA can uncover this subtle conduction propagation with reliable accuracy, improving the veracity of activation mapping, and helping guide subsequent ablation.

Transcoronary mapping with an over-the-wire multielectrode catheter in scar-related ventricular tachycardia patients.

AIMS: The usefulness of coronary venous system mapping has been reported for assessing intramural and epicardial substrates in patients with scar-related ventricular tachycardia (VT). However, there has been little data on mapping from coronary arteries. We investigated the safety and utility of mapping from coronary arteries with a novel over-the-wire multielectrode catheter in scar-related VT patients. METHODS AND RESULTS: Ten consecutive scar-related VT patients with non-ischaemic cardiomyopathy who underwent mapping from a coronary artery were analysed. Six patients underwent simultaneous coronary venous mapping. High-density maps were created by combining the left ventricular endocardium and coronary vessels. Substrate maps were created during the baseline rhythm with 2438 points (IQR 2136-3490 points), including 329 (IQR 59-508 points) in coronary arteries. Abnormal bipolar electrograms were successfully recorded within coronary arteries close to the endocardial substrate in seven patients. During VT, isthmus components were recorded within the coronary vessels in three patients with no discernible isthmus components on endocardial mapping. The ablation terminated the VT from an endocardial site opposite the earliest site in the coronary arteries in five patients. CONCLUSION: The transcoronary mapping with an over-the-wire multielectrode catheter can safely record abnormal bipolar electrograms within coronary arteries. Additional mapping data from the coronary vessels have the potential to assess three-dimensional ventricular substrates and circuit structures in scar-related VT patients.

Delineation of conduction gaps of linear lesions during atrial fibrillation ablation using ultra-high-density mapping.

AIMS: Linear lesions are routinely created by radiofrequency catheter ablation. Unwanted electrical conduction gaps can be produced and are often difficult to ablate. This study aimed to clarify the characteristics of conduction gaps during atrial fibrillation ablation by analysing bidirectional activation maps using a high-density mapping system (RHYTHMIA). METHODS AND RESULTS: This retrospective study included 31 patients who had conduction gaps along pulmonary vein (PV) isolation or box ablation lesions. Activation maps were sequentially created during pacing from the coronary sinus and PV to reveal the earliest activation site, defined by the entrance and exit. The locations, length between the entrance and exit (gap length), and direction were analysed. Thirty-four bidirectional activation maps were drawn: 21 were box isolation lesions (box group), and 13 were PV isolation lesions (PVI group). Among the box group, nine conduction gaps were present in the roof region and 12 in the bottom region, while nine in right PV and four in left PV among the PVI group. Gap lengths in the roof region were longer than those in the bottom region (26.8 ± 11.8 vs. 14.5 ± 9.8 mm; P = 0.022), while those in right PV tended to longer than those in left PV (28.0 ± 15.3 vs. 16.8 ± 8.0 mm, P = 0.201). CONCLUSION: The entrances and exits of electrical conduction gaps were separated, especially in the roof region, indicating that epicardial conduction might contribute to gap formation. Identifying the bidirectional conduction gap might indicate the location and direction of epicardial conduction.

Epicardial connections and bi-atrial tachycardias: From anatomy to clinical practice.

Bi-atrial tachycardia (BiAT) is not rare after extensive atrial ablation or cardiac surgery. The complexity of bi-atrial reentrant circuits poses a great challenge for clinical practice. With recent advances in mapping technologies, we are now able to characterize atrial activation in detail. However, given the involvement of both atria and multiple epicardial conductions, endocardial mapping for BiATs is not easy to understand. Knowledge of the atrial myocardial architecture is the foundation for the clinical management of BiATs; as it is required to understand the possible mechanism of the tachycardia and identify the optimal target of ablation. In this review we summarize current knowledge about the anatomy of interatrial connections as well as other epicardial fibers and discuss the interpretation of electrophysiological findings and ablation strategies for BiATs.

High density mapping of complex atrial tachycardia in patients after cardiac surgery.

To provide an overview of the current application of high-density mapping (HDM) in the mechanism of complex atrial tachycardias (ATs). Complex ATs are frequently scar-related, after history of previous cardiac surgery and large scars. These scar-related ATs are difficult to manage medically and frequently recur after electrical cardioversion. HDM technologies have enabled rigorous elucidation of AT mechanisms in patients post cardiac surgery. This article showed the application of HDM technology in complex ATs from the mechanisms of complex ATs, the development of HDM technology, and the identification of scars or critical isthmus from HDM. HDM-guided approach is highly effective for identifying the ATs mechanism and critical isthmus.

Detection of a unidirectional epicardial connection between the right-sided pulmonary venous carina and the right atrium by pacing from a high-density mapping catheter.

We report a case of recurring, persistent atrial fibrillation (AF) in a patient with a unidirectional epicardial connection (EC) between the right-sided pulmonary venous (PV) carina and the right atrium detected using a high-density mapping catheter with a steerable introducer support, but not a conventional circular mapping catheter. This unidirectional EC could be steadily abolished by a radiofrequency delivery. Finally, we were able to successfully achieve complete PV antrum isolation. Thereafter, he has remained well without any AF.

Long-term success of a multi-electrode substrate mapping and ablation strategy versus a classic single tip mapping and ablation strategy for ventricular tachycardia ablation in patients with ischemic cardiomyopathy.

INTRODUCTION: Over the past years, mapping and ablation techniques for the treatment of ventricular tachycardia (VT) have evolved rapidly. High Density (HD) substrate mapping is now routine and pre-procedural imaging is increasingly used. The additional value of these techniques for long-term VT-free survival is not clear. METHODS: We compared baseline and procedural characteristics, procedural success, safety and outcome of mapping and ablation of ventricular tachycardia in patients with ischemic heart disease between two groups. (1) Low Density (LD) group: VT mapping and ablation with a 4 mm single tip catheter (2) HD group: HD substrate mapping with the Pentaray (Biosense Webster, USA) or HD Grid (Abbott, USA) catheter and ablation with a 4 mm single tip catheter. RESULTS: VT ablation was performed in 133 patients (71 patients in LD group and 62 patients in HD group). The median follow-up was 5.0 years in LD group and 2.0 years in HD group. One-, two-, and five-year VT recurrence rates were 47%, 56%, and 65% in the LD group versus 39%, 50%, and 55% in the HD group (log-rank test for VT recurrence p = .70). One-, two-, and five-year ICD shock recurrence rates were 14%, 18%, and 24% in the LD group versus 8%, 15%, and 19% in the HD group (log-rank test for ICD-shock p = .79). All-cause mortality, cardiac (non-arrhythmic), and arrhythmic death, were similar in both groups. Severe procedural complications (tamponade, stroke, or procedural death) occurred in four patients (5%, 1 vascular, 3 tamponade) in the LD group versus two patients (3%, both tamponade) in the HD group (NS). In univariate and multivariable analysis, only a higher LVEF was significantly associated with VT-free survival. HD mapping was not significantly associated with VT-free survival. Anterior infarct location and age were significantly associated with ICD recurrent shock in both univariate and multivariable analyses. CONCLUSIONS: In patients with ischemic cardiomyopathy, a HD substrate mapping, and ablation strategy did not lead to higher VT-free survival and shock-free survival compared to a single tip mapping and ablation strategy. In this study, only LVF is an independent predictor for VT recurrence. Anterior infarct location and age predict recurrent ICD shocks.