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Centrifugal activation is not always the origin of a focal atrial tachycardia (AT) ("true-focal"), but passive activation from the other structures ("pseudo-focal").We aimed to establish a method to differentiate true-focal from pseudo-focal.In 49 centrifugal activations in 35 patients with AT, 12-lead electrocardiogram, activation map, atrial global activation histogram (GAH), and local electrograms were analyzed. GAH demonstrates the relation between the activation area and timing through the cycle length, displayed with a normalized value, ranging from 0 (smallest activation area) to 1.0 (largest activation area).Of 30 centrifugal activations observed in the septal region, 6/30 (20.0%) were true-focal. The remaining 24/60 (80.0%) were pseudo-focal, of which 23 (95.8%) were from the opposite chamber. P-wave/flutter-wave duration200 ms discriminated true-focal from pseudo-focal (sensitivity 100%; specificity 54.5%; positive predictive value 33.3%; negative predictive value 100%). Multiple breakthrough ruled out the possibility of a true-focal AT. Other differentiating factors were an activation area within the initial 20 ms of5 mmCentrifugal activation is not necessarily due to a focal AT but passive activation. The activation map with GAH in addition to the 12-lead electrocardiogram and local electrograms enables an accurate differentiation.

Background: Achieving bidirectional mitral isthmus (MI) block using radiofrequency catheter ablation (RFCA) alone is challenging, and MI reconnection is common. Adjunctive vein of Marshall (VOM) ethanol infusion (VOM-Et) can facilitate acute MI block. However, little is known about its long-term success. This study sought to evaluate the impact of adjunctive VOM-Et on MI block achievement and durability compared with RFCA alone. Methods: Patients undergoing the first attempt of posterior MI ablation were grouped according to their MI block index strategy: adjunctive VOM-Et and RFCA alone. Rates of acute MI block and MI reconnection observed during repeat procedures were compared between the 2 groups. Results: The VOM-Et group consisted of 152 patients (63.8±9.4 years) undergoing adjunctive VOM-Et for MI block. The RFCA group consisted of 110 patients (60.9±9.2 years) undergoing MI ablation using RFCA alone. Acute MI block was more frequently achieved in the VOM-Et group (98.7% [150/152] versus 63.6% [70/110]; P P P P =0.008). Conclusions: Beyond facilitating acute MI block, VOM-Et is associated with greater lesion durability as evidenced by higher rates of MI block during repeat procedures.

Background Determining the etiology of syncope is challenging in Brugada syndrome (BrS) patients. Implantable cardioverter defibrillator placement is recommended in BrS patients who are presumed to have arrhythmic syncope. However, arrhythmic syncope in BrS patients can occur in the setting of atrioventricular block (AVB), which should be managed by cardiac pacing. The clinical characteristics of BrS patients with high-risk AVB remain unknown. Methods This study included 223 BrS patients with a history of syncope from two centers. The clinical characteristics of patients with high-risk AVB (Mobitz type II second-degree AVB, high-degree AVB, or third-degree AVB) were investigated. Results During the 99 ± 78 months of follow-up, we identified six BrS patients (2.7%) with high-risk AVB. Three of the six patients (50%) with AVB presented with syncope associated with prodromes or specific triggers. Four patients (67%) were found to have paroxysmal third-degree AVB during the initial evaluation for BrS and syncope, while two patients developed third-degree AVB during the follow-up period. The incidence of first-degree AVB was significantly higher in AVB patients than in non-AVB patients (83% vs. 15%; p = .0005). There was no significant difference in the incidence of ventricular fibrillation between AVB and non-AVB patients (AVB [17%], non-AVB [12%]; p = .56). Conclusion High-risk AVB can occur in BrS patients with various clinical presentations. Although rare, the incidence is worth considering, especially in BrS patients with first-degree AVB.

Background: Studies of ventricular fibrillation (VF) in humans are limited because of the short available duration. We sought to study surface ECG waveforms and effect of ablation in long-lasting VF in patients with left assist devices. Methods: Continuous 12-lead ECG of 5 episodes of long-lasting VF occurring in 3 patients with left ventricular assist device were analyzed. Spectral analysis (dominant frequency) and quantification of waveform amplitude, regularity (Unbiased Regularity Index), and complexity (Nondipolar Index) were performed over a median of 24 minutes of VF. Radiofrequency ablation was performed during VF in 2 patients. Results: There was a significant increase in dominant frequency between VF onset and termination but none of the other parameters significantly changed. Some VF parameters varied from patient to patient and from lead to lead. Dominant frequency decreased after radiofrequency ablation in both cases and VF terminated spontaneously shortly after ablation in one case. The previously incessant VFs in these 2 patients did not recur afterward. Conclusions: VF rate increases over time in patients with left ventricular assist devices and is lowered by ablation. Long-lasting VF may be modified or even terminated by ablation.

Background The QDOT MICRO catheter allows temperature- and flow-controlled (TFC) ablation and very-high-power short-duration (vHPSD) ablation. Objective The purpose of this study was to compare lesion characteristics between TFC/vHPSD ablation and standard power-controlled (PC) ablation. Methods Lesion characteristics in the right atrium, left atrium, and right ventricle (RV) of 6 sheep were compared between vHPSD (90 W/4 seconds, TC mode with 60°C target using QDOT) and standard radiofrequency settings (PC mode, 30 W/30 seconds with ThermoCool SmartTouch SF). Lesions in the left ventricle (LV) were compared, targeting 50 W for 60-second applications. Results Forty-six focal atrial lesions, 50 RV focal lesions, and 12 linear lesions were created by vHPSD ablation and PC ablation in each group of 6 animals. vHPSD ablation produced significantly larger focal atrial lesions in length (8.3 [6.4–9.7] mm vs 6.3 [5.2–7.4] mm; P = .0002), width (6.0 [5.3–6.9] mm vs 4.6 [3.8–5.4] mm; P Conclusion TFC/vHPSD ablation produces larger, shallower, more homogeneous, and less hemorrhagic lesions. vHPSD Ablation produces more transmural and contiguous linear lesions compared to PC ablation. LV lesions are more homogeneous with fewer steam pops in TFC ablation.

Atrial fibrillation is the most common sustained cardiac arrhythmia and is associated with considerable morbidity and mortality. Electrically isolating the pulmonary veins from the left atrium by catheter ablation is superior to antiarrhythmic drug therapy for maintaining sinus rhythm, but its success varies depending on multiple factors, including arrhythmic burden. Although procedural outcomes have improved over the years, further gains are limited by a seemingly zero-sum relationship between effectiveness and safety, which is largely a product of the available technologies. Current energies used to create contiguous, transmural, and durable atrial lesions can result in serious complications if they reach the esophagus or phrenic nerve, for instance—structures that can be adjacent to the atrial myocardium, often within millimeters of the energy source. Consequently, high rates of pulmonary vein-left atrium reconnections are consistently seen in clinical studies and in clinical practice as operators appropriately forgo ablation effectiveness to protect patients from harm. However, as ablative technologies evolve to circumvent this stalemate, safer, and more effective pulmonary vein isolation seems increasingly realistic. Furthermore, the innovative nature of these technologies raises the prospect of markedly improved procedural efficiency, which could increase patient comfort, reduce operator occupational injuries, and enhance the use of health resources—all of which are increasingly important considerations particularly as the demand for catheter ablation for atrial fibrillation continues to rise. We herein review 3 promising candidate ablation technologies with the potential to revolutionize the management of patients with atrial fibrillation: electroporation (pulsed-field ablation), expandable lattice-tip radiofrequency ablation/electroporation, and ultra-low temperature cryoablation.

Background Gaps in the roof line have been ascribed to epicardial conduction using the septopulmonary bundle. Objectives We sought to evaluate the frequency of septopulmonary bundle bypass during roof line ablation, to describe anatomical conditions favoring this epicardial gap, and to propose an alternative strategy when present. Methods One hundred consecutive patients underwent atrial fibrillation ablation. A de novo roof line was created between the superior pulmonary veins. In cases of residual gaps, a floor line was created between the inferior pulmonary veins. Microtomography imaging and histological analyses of 5 human donor hearts were performed: a specific focus was made on the dome and the posterior wall. Results Residual gaps were more frequent in roof lines than floor lines (33% vs 15%; P = .049). Electrogram morphologies, activation sequences, and pacing maneuvers indicated an epicardial bypass of the roof line in all cases. Conduction block was obtained in 67 roof lines and 28 floor lines, resulting in a 95% success rate of linear block, without "box" isolation. Between the superior pulmonary veins, the atrial myocardium was thicker and consistently displayed adipose tissue separating the septopulmonary bundle from the septoatrial bundle. Conclusion Epicardial conduction across the roof line is common and requires careful electrogram analysis to detect. In such cases, a floor line can be an effective alternative strategy, with clear validation criteria. Myocardial thickness and fat interposition may explain difficulties in achieving lesion transmurality during roof line ablation.

Activation mapping using noninvasive electrocardiographic imaging (ECGi) has recently been used to describe the physiology of different cardiac abnormalities. These descriptions differ from prior invasive studies, and both methods have not been thoroughly confronted in a clinical setting.The goal of the present study was to provide validation of noninvasive activation mapping in a clinical setting through direct confrontation with invasive epicardial contact measures.Fifty-nine maps were obtained in 55 patients and aligned on a common geometry. Nearest-neighbor interpolation was used to avoid map smoothing. Quantitative comparison was performed by computing between-map correlation coefficients and absolute activation time errors.The mean activation time error was 20.4 ± 8.6 ms, and the between-map correlation was poor (0.03 ± 0.43). The results suggested high interpatient variability (correlation -0.68 to 0.82), wide QRS patterns, and paced rhythms demonstrating significantly better mean correlation (0.68 ± 0.17). Errors were greater in scarred regions (21.9 ± 10.8 ms vs 17.5 ± 6.7 ms; P.01). Fewer epicardial breakthroughs were imaged using noninvasive mapping (1.3 ± 0.5 vs 2.3 ± 0.7; P.01). Primary breakthrough locations were imaged 75.7 ± 38.1 mm apart. Lines of conduction block (jumps of ≥50 ms between contiguous points) due to structural anomalies were recorded in 27 of 59 contact maps and were not visualized at these same sites noninvasively. Instead, artificial lines appeared in 33 of 59 noninvasive maps in regions of reduced bipolar voltage amplitudes (P = .03). An in silico model confirms these artificial constructs.Overall, agreement of ECGi activation mapping and contact mapping is poor and heterogeneous. The between-map correlation is good for wide QRS patterns. Lines of block and epicardial breakthrough sites imaged using ECGi are inaccurate. Further work is required to improve the accuracy of the technique.

Catheter ablation for ventricular tachycardia (VT) has been increasingly used over the past two decades in patients with structural heart disease (SHD). In these individuals, a substrate mapping strategy is being more commonly applied to identify targets for VT ablation, which has been shown to be more effective versus targeting mappable VTs alone. There are a number of substrate mapping methods in existence that aim to explore potential VT isthmuses, although their success rates vary. Most of the reported electrogram-based mapping studies have been performed with ablation catheters; meanwhile, the use of multipolar mapping catheters with smaller electrodes and closer interelectrode spacing has emerged, which allows for an assessment of detailed near-field abnormal electrograms at a higher resolution. Another recent advancement has occurred in the use of imaging techniques in VT ablation, particularly in refining the substrate. The goal of this paper is to review the key developments and limitations of current mapping strategies of substrate-based VT ablation and their outcomes. In addition, we briefly summarize the role of cardiac imaging in delineating VT substrate.

Successful mapping and ablation of ventricular tachycardias remains a challenging clinical task. Whereas conventional entrainment and activation mapping was for many years the gold standard to identify reentrant circuits in ischaemic ventricular tachycardia ablation procedures, substrate mapping has become the cornerstone of ventricular tachycardia ablation. In the last decade, technology has dramatically improved. In parallel to high-density automated mapping, cardiac imaging and image integration tools are increasingly used to assess the structural ventricular tachycardia substrate. The aim of this review is to describe the technologies underlying these new mapping systems and to discuss their possible role in providing new insights into identification and visualization of reentrant tachycardia mechanisms.

Ventricular fibrillation (VF) is a common and life-threatening arrhythmia resulting in sudden cardiac death (SCD). Due to the inherent challenges of mapping VF in humans, the underlying mechanisms that initiate and sustain this common arrhythmia are still poorly understood. In high-risk patients and survivors of SCD, implantable cardioverter defibrillators (ICD) play a central role in treating VF episodes, however, ICDs do not prevent VF recurrences and patients remain at risk of electrical storm and multiple shocks that are often refractory to escalation of medical therapy. More recently, the utility of catheter ablation (CA) has extended to the treatment of VF storms. This review will focus on updates in elucidating the mechanism of VF leading into the role and indication of CA as a treatment strategy.

BACKGROUND Radiofrequency (RF) power is routinely considered during RF application. In contrast, impedance has been relatively poorly studied, despite also influencing RF lesion creation. The aim of this study was to examine the influence of electric impedance on RF lesion characteristics and on clinical RF ablation parameters. METHODS AND RESULTS In the first part of the study, power and impedance were systematically varied and the resulting current was calculated using custom-made software. In the second part of the study, ablation lesions (n = 40) were analyzed in a porcine ex vivo model. RF applications were delivered in cardiac muscle preparations with systematically varied values of electric impedance using a contact force ablation catheter. In the third part of the study, n = 3378 clinical RF applications were analyzed, power, impedance, and current data were exported and correlated with clinical patient data. 20 ± 3 W/80 Ω, 30 ± 3 W/120 Ω, 40 ± 3 W/160 Ω, and 50 ± 3 W/200 Ω RF applications resulted in 498 ± 40, 499 ± 26, 500 ± 20, and 500 ± 16 mA RF current, which were not significantly different (p = .32). Ablation lesions were significantly different in depth and diameter when applied with the same power but different impedances (p

Voltage criteria for ventricular mapping have been obtained from small series of patients and prioritizing high specificity.The purpose of this study was to analyse the potential influence of contact force (CF) on voltage mapping and to define voltage cutoff values for right ventricular (RV) scar using the tetralogy of Fallot as a model of transmural RV scar and magnetic resonance imaging (MRI) as reference.Fourteen patients (age 32.6 ± 14.3 years; 5 female) with repaired tetralogy of Fallot underwent high-resolution cardiac MRI (1.25 × 1.25 × 2.5 mm). Scar, defined as pixels with intensity50% maximum, was mapped over the RV geometry and merged within the CARTO system to RV endocardial voltage maps acquired using a 3.5-mm ablation catheter with CF technology (SmartTouch, Biosense Webster).In total, 2446 points were analyzed, 915 within scars and 1531 in healthy tissue according to MRI. CF correlated to unipolar (ρ = 0.186; P.001) and bipolar voltage in healthy tissue (ρ = 0.245; P.001) and in scar tissue. Receiver operating characteristic curve analysis excluding points with very low CF (5g) identified optimal voltage cutoffs of 5.19 mV for unipolar voltage and 1.76 mV for bipolar voltage, yielding sensitivity/specificity of 0.89/0.85 and 0.9/0.9, respectively.CF is an important factor to be taken into account for voltage mapping. If good CF is applied, unipolar and bipolar voltage cutoffs of 5.19 mV and 1.76 mV are optimal for identifying RV scar on endocardial mapping with the SmartTouch catheter. Data on the diagnostic accuracy of different voltage cutoff values are provided.

Anatomic macroreentrant atrial tachycardias (MATs) are conventionally reported to depend on the cavotricuspid isthmus, the mitral isthmus, or the left atrial roof, and are commonly seen following catheter ablation for atrial fibrillation.To define the precise circuits of anatomic MAT with ultrahigh-resolution mapping.In 57 patients (mean age, 62 years; 10 female) who developed ≥1 anatomic MAT, we analyzed 88 MAT circuits including 16 peritricuspid, 42 perimitral, and 30 roof-dependent circuits, using high-density mapping and entrainment.Of 16 peritricuspid atrial tachycardias (ATs), 8 (50.0%) showed a circuit not limited to the tricuspid annulus. However, cavotricuspid isthmus ablation terminated the tachycardia in all patients. Similarly, 26 of 42 perimitral ATs (61.9%) showed a circuit not limited to the mitral annulus, and a low-voltage zone0.1 mV around the mitral annulus was associated with nontypical perimitral ATs (P.0001). The practical isthmus was not in the mitral isthmus in 13 of these 26 perimitral ATs (50%). Finally, 22 of 30 roof-dependent ATs (73.3%) had a circuit not rotating around both pairs of pulmonary veins. Brief assessment of the activation direction on the posterior wall in relation to that on the septal, anterior, and lateral wall helped deduce the circuit of roof-dependent AT in 27 of 30 (90.0%). Practical isthmus was not in the roof in 8 of 22 (36.4%). Practical isthmuses mapped with the system were significantly shorter than the usual anatomic isthmuses (16.1 ± 8.2 mm vs 33.7 ± 10.4 mm) (P.0001).High-density mapping successfully identified the precise circuits and the practical isthmus of anatomic MATs in patients with prior atrial fibrillation ablation.

Aims To compare the arrhythmic response to isoproterenol and exercise testing in newly diagnosed arrhythmogenic right ventricular cardiomyopathy (ARVC) patients. Methods and results We studied isoproterenol [continuous infusion (45 µg/min) for 3 min] and exercise testing (workload increased by 30 W every 3 min) performed in consecutive newly diagnosed ARVC patients. Both tests were evaluated with regard to the incidence of (i) polymorphic premature ventricular contractions (PVCs) and couplet(s) or (ii) sustained or non-sustained ventricular tachycardia (VT) with left bundle branch block [excluding right ventricular outflow tract VT]; and compared to a control group referred for the evaluation of PVCs without structural heart disease. Thirty-seven ARVC patients (63.5% male, age 38 ± 16 years) were included. The maximal sinus rhythm heart rate achieved during isoproterenol testing was significantly lower compared to exercise testing (149 ± 17 bpm vs. 166 ± 19 bpm, P

Background The significance of fractionated electrograms (EGMs) is object of debate, with multiple mechanisms described. Objective Using Rhythmia, a high-density mapping system, we sought to investigate the relationship between specific electrophysiological phenomena and EGM characteristics at those sites. Methods Twenty-five consecutive patients underwent high-density atrial mapping during atrial tachycardias. Bipolar EGMs were recorded with a 64-electrode basket catheter. The following atrial phenomena were identified: slow conduction (SC) areas, lines of block (LB), wavefront collisions (WFC), pivot sites (PS), and gaps. EGMs collected at these predefined areas were analyzed in terms of amplitude, duration, and morphology. Results Twenty-five atrial maps with 195 sites of interest (1755 EGMs) were object of our analysis. Thirty-five percent were sites of SC: fractionation had low amplitude (0.16 ± 0.07 mV) and long duration (87.8 ± 10.7 ms); wavefront collisions were seen in 38% of sites with EGMs shorter in duration (46.5 ± 4.5 ms) and higher in voltage (0.58 ± 0.13 mV); 17% were lines of block, never responsible for fractionation (0.13 ± 0.05 mV; 122.4 ms ± 24.8 ms); 9% were PS with a high degree of fractionation (0.55 ± 0.15 mV; 85.8 ± 7.9 ms). Two gaps were identified (1%) with a low degree of fractionation. Conclusion Specific EGM characteristics in atrial tachycardia can be reproducibly linked to electrophysiological mechanisms. High-voltage and short-duration EGMs are associated with collision sites and PS that are unlikely to form critical sites for ablation; long-duration, low-voltage EGMs are associated with SC. However, not all SC regions will lie within the critical circuit and identification by only EGM characteristics cannot guide ablation.

Objectives This study sought to assess the relationship between fibrosis and re-entrant activity in persistent atrial fibrillation (AF). Background The mechanisms involved in sustaining re-entrant activity during AF are poorly understood. Methods Forty-one patients with persistent AF (age 56 ± 12 years; 6 women) were evaluated. High-resolution electrocardiographic imaging (ECGI) was performed during AF by using a 252-chest electrode array, and phase mapping was applied to locate re-entrant activity. Sites of high re-entrant activity were defined as re-entrant regions. Late gadolinium-enhanced (LGE) cardiac magnetic resonance (CMR) was performed at 1.25 × 1.25 × 2.5 mm resolution to characterize atrial fibrosis and measure atrial volumes. The relationship between LGE burden and the number of re-entrant regions was analyzed. Local LGE density was computed and characterized at re-entrant sites. All patients underwent catheter ablation targeting re-entrant regions, the procedural endpoint being AF termination. Clinical, CMR, and ECGI predictors of acute procedural success were then analyzed. Results Left atrial (LA) LGE burden was 22.1 ± 5.9% of the wall, and LA volume was 74 ± 21 ml/m 2 . The number of re-entrant regions was 4.3 ± 1.7 per patient. LA LGE imaging was significantly associated with the number of re-entrant regions (R = 0.52, p = 0.001), LA volume (R = 0.62, p Conclusions The number of re-entrant regions during AF relates to the extent of LGE on CMR, with the location of these regions clustering to LGE areas. These characteristics affect procedural outcomes of ablation.

Objectives This study sought to map the epicardial electrophysiological (EP) substrate in early repolarization (ER) syndrome patients using noninvasive electrocardiographic imaging (ECGI), and to characterize substrate properties that support arrhythmogenicity. Background The ER pattern is a common ECG finding. Recent studies established a definitive clinical association between ER and fatal ventricular arrhythmias. However, the arrhythmogenic substrate of ER in the intact human heart has not been characterized. Methods Twenty-nine ER syndrome patients were enrolled, 17 of whom had a malignant syndrome. Characteristics of the abnormal EP substrate were analyzed using data recorded during sinus rhythm. The EP mapping data were analyzed for electrogram morphology, conduction, and repolarization. Seven normal subjects provided control data. Results The abnormal EP substrate in ER syndrome patients has the following properties: 1) abnormal epicardial electrograms characterized by presence of J waves in localized regions; 2) absence of conduction abnormalities, including delayed activation, conduction block, or fractionated electrograms; and 3) marked abbreviation of ventricular repolarization in areas with J waves. The action potential duration (APD) was significantly shorter than normal (196 ± 19 ms vs. 235 ± 21 ms; p Conclusions ER is associated with steep repolarization gradients caused by localized shortening of APD. Results suggest association of PVC initiation sites with areas of repolarization abnormalities. Conduction abnormalities were not observed.

Introduction Micro Computed tomography has emerged as a powerful imaging tool to study the micro-structure of cardiac tissue of small mammals. However, conventional techniques in whole organs of large mammals, is compromised due to the use of high molecular weight contrast agents and the relative thickness of samples. Objective To develop a tissue preparation method to optimize microCT imaging of whole hearts with sizes including those of humans. Methods Male pig hearts (N = 5) were treated by: hydrated samples with conventional contrast agent (iodine, 0.5%) or dehydrated in ethanol and air-dried under hexamethyldisilazane (HMDS). Human hearts (N = 3) were treated using air-drying method. Hearts were imaged at 21.7 μm isotropic resolution by microCT (SkyScan 1276 Bruker). Images were quantified with Amira software using a 3D cylinder correlation technique. Results The X-ray attenuation of air-dried samples was better optimized for the bandwidth of the X-ray detector, indicated by reduced x-ray attenuation (pig 65%, human 55), compared to almost complete signal attenuation from hydrated samples (93%). Voxel intensity histograms showed two populations corresponding to the tissue and the background media and sample support structures. Yet, the separating minima of histogram intensities were always observed at lower intensities for air-dried hearts ( Fig. 1 A) than hydrated hearts, increasing the dynamic range for tissue-specific signals ( Fig. 1 B). Imaging air-dried pig or human hearts permitted a simple threshold-based segmentation to isolate microstructures of the heart, including vessels, myocardial fibers and Purkinje from the background (1C). Fiber orientation quantification could be performed directly on unfiltered images. Fiber orientation was validated against subsequent histology of the same samples. Conclusion Air drying with HMDS enables microCT imaging of human-sized hearts while preserving micro-structure and the identification of individual cardiac muscle fibers.

Background: Atrial fibrillation ablation–related atrial tachycardia (AT) is complex and may demonstrate several forms: anatomic macroreentrant AT (AMAT), non-AMAT, and focal AT. We aimed to elucidate the recurrence rate and mechanisms of atrial fibrillation ablation–related AT recurrence. Methods: Among 147 patients with ATs treated with the Rhythmia system, 68 (46.3%) had recurrence at mean 4.2 (2.9–11.6) months, and 44 patients received a redo procedure. AT circuits in the first procedure were compared with those in the redo procedure. Results: Although mappable ATs were not observed in 7 patients, 68 ATs were observed in 37 patients during the first procedure: perimitral flutter (PMF) in 26 patients, roof-dependent macroreentrant AT (RMAT) in 18, peritricuspid flutter in 10, non-AMAT in 14, and focal AT in 3. During the redo AT ablation procedure, 54 ATs were observed in 41/44 patients: PMF in 24, RMAT in 14, peritricuspid flutter in 1, non-AMAT in 14, and focal AT in 1. Recurrence of PMF and RMAT was observed in 15 of 26 (57.7%) and 8 of 18 (44.4%) patients, respectively, while peritricuspid flutter did not recur. Neither the same focal AT nor the same non-AMAT were observed except in 1 case with septal scar–related biatrial AT. Epicardial structure–related ATs were involved in 18 of 24 (75.0%) patients in PMF, 4 of 14 (28.6%) in RMAT, and 4 of 14 (28.6%) in non-AMAT. Of 21 patients with a circuit including epicardial structures, 6 patients treated with ethanol infusion in the vein of Marshall did not show any AT recurrence, although 8 of 15 (53.3%) treated with radiofrequency showed AT recurrence ( P =0.04). Conclusions: Although high-resolution mapping may lead to correct diagnosis and appropriate ablation in the first procedure, the recurrence rate is still high. The main mechanism of atrial fibrillation ablation–related AT is the recurrence of PMF and RMAT or non-AMAT different from the first procedure. Epicardial structures (eg, coronary sinus/vein of Marshall system) are often involved, and ethanol infusion in the vein of Marshall may be an additional treatment.

Early repolarization indicates an electrocardiographic phenotype affecting the junction (J wave) between the QRS complex and the ST segment in inferolateral leads. Here, we report a patient surviving a ventricular fibrillation in whom therapeutic mild hypothermia caused a major increase in J-wave and an arrhythmic storm. Other similar cases in the literature are discussed. Their analysis supports a potential diagnostic role of hypothermic methods in the risk assessment of J- wave syndromes.

Persistent left superior vena cava (LSVC) is the most common thoracic venous anomaly. It is frequently implicated in atrial fibrillation initiation and maintenance in patients who harbor them, as exemplified by this case study. The LSVC is in continuity with the CS and can be disconnected from the left atrium to which it is connected by multiple myocardial bridges, creating an ideal substrate for rapid reentry.

We present a 40-year old patient with symptomatic persistent AF. This case illustrates the importance of thoracic veins in the pathogenesis of atrial fibrillation. In this case, PV isolation resulted in a drastic cycle length prolongation with AF persisting with periods of organized activation sequence allowing for localization of the culprit area: a bursting SVC, whose isolation led to sinus resumption.

Background: Various strategies for ablation of ventricular tachycardia (VT) have been described, but their impact on ventricular fibrillation (VF) is largely unknown. The aim of our study was to assess the effect of substrate-based VT ablation targeting local abnormal ventricular activity (LAVA) on recurrent VF events in patients with structural heart disease. Methods: A retrospective 2-center study was performed on patients with structural heart disease and both VT and VF, with incident VT ablation procedures targeting LAVAs. Generalized estimating equations with a Poisson loglinear model were used to assess the impact of catheter ablation on VF episodes. The change in VF events before and after catheter ablation was compared with matched controls without ablation. Results: From a total of 686 patients with an incident VT ablation procedure targeting LAVAs, 21 patients (age, 57±14 years; left ventricular ejection fraction, 30±10%) had both VT and VF and met inclusion criteria. A total of 80 VF events were recorded in the implantable cardioverter-defibrillator logs the 6 months preceding ablation. Complete and partial LAVA elimination was achieved in 11 (52%) and 10 (48%) patients, respectively. Catheter ablation was associated with a highly significant reduction in VF recurrences ( P P =0.0003). Conclusions: Substrate-guided VT ablation targeting LAVAs may be associated with a significant reduction in recurrent VF, suggesting that VT and VF share overlapping arrhythmogenic substrates in patients with structural heart disease.

Background Atrioventricular (AV) node duality is suggested by several electrophysiological findings, none of which are strong predictors of AV nodal reentrant tachycardia (AVNRT). Objective The purpose of this study was to propose a novel maneuver to study conduction over the AV node and attempt to induce slow-fast AVNRT. Methods Ventricular-triggered atrial pacing (VTAP) with decremental VA delay was carried out in 36 consecutive patients with slow-fast AVNRT and in 21 controls after conventional electrophysiology study. Maneuvers were repeated after ablation in patients with AVNRT. Results VTAP resulted in a hysteretic conduction curve in 21 of 36 patients (58%) in the AVNRT group but only 4 of 21 patients (19%) in the control group (sensitivity 58; specificity 81%). This finding demonstrates sustained conduction in a slow conducting pathway and concealed retrograde conduction over a fast pathway. VTAP resulted in AVNRT induction in 15 of 25 inducible patients at baseline (60%), 4 of which were not inducible with incremental pacing or programmed atrial stimulation. VTAP resulting in a suspended p wave had 51% (39%–64%) sensitivity and 100% (89%–100%) specificity for predicting noninducibility in a given autonomic state. Conclusion VTAP is useful in patients with suspected slow-fast AVNRT. A hysteretic conduction curve demonstrates sustained conduction over a slow pathway and concealed retrograde conduction through the fast pathway, a finding in favor of slow-fast AVNRT. VTAP may facilitate AVNRT induction and proves to be an interesting complement to classic maneuvers. A suspended p-wave response specifically predicts noninducibility of slow-fast AVNRT in a given autonomic state, providing an interesting surrogate to noninducibility as a procedural end point.

Idiopathic ventricular fibrillation and J-wave syndromes are causes of sudden cardiac death (SCD) without any identified structural cardiac disease after extensive investigations. Recent data show that high-density electrophysiological mapping may ultimately offer diagnoses of subclinical diseases in most patients including those termed "unexplained" SCD. Three major conditions can underlie the occurrence of SCD: (1) localized depolarization abnormalities (due to microstructural myocardial alteration), (2) Purkinje abnormalities manifesting as triggering ectopy and inducible reentry; or (3) repolarization heterogeneities. Each condition may result from a spectrum of pathophysiologic processes with implications for individual therapy.

The incidence of atrial fibrillation (AF) in Brugada syndrome (BrS) has been reported at between 9% and 53% by different series, but the true prevalence is unknown. However, AF may be the presenting feature in some patients. The underlying mechanisms for AF may be a combination of multiple factors, genetic or acquired, that may impact upon autonomic function, atrial structure, and conduction velocities or other unknown factors. The presence of AF has been associated with a more malignant course, with a greater incidence of syncope and ventricular arrhythmias, thus acting as marker of more advanced disease. Regarding the management of patients with AF, antiarrhythmic drugs effective in preventing malignant arrhythmias in BrS such as quinidine or invasive treatment with pulmonary vein isolation (PVI) may be useful in AF treatment. In this review, we aim to present the current perspectives regarding the genetics, pathophysiology, management, and prognosis of AF in patients with BrS.

BACKGROUND: Pulmonary vein isolation remains the cornerstone of atrial fibrillation (AF) ablation. However, due to high recurrence rates, especially in patients with persistent AF, PV antral isolation, complemented by linear ablation, autonomic modulation, and ablation of complex fractionated electrograms, have been attempted to increase the odds of success. However, the optimum approach for a complementary strategy in addition to PVI for persistent AF is unknown. METHODS: We performed a prospective randomized trial by assigning 92 patients with persistent AF in 1:1 ratio to pulmonary-vein isolation plus ablation of electrograms showing complex fractionated activity (45 patients), or pulmonary-vein isolation plus additional linear ablation across the left atrial roof and mitral valve isthmus (47 patients). The duration of follow-up was five years. The primary endpoint was freedom from any documented recurrence of atrial fibrillation after a single ablation procedure. RESULTS: At a 12-month follow-up, 9 (23%) patients had AF recurrence in the linear ablation and 8 (21%) patients in the CFAE groups. At a mean follow-up duration of 59±36 months, 48.3% of patients in the linear ablation group and 44.6% of patients in the CFAE group were free from AF (p=0.403). There were no significant differences between the two groups for independent predictors of freedom from AF. The overall procedure time and radiation exposure were higher in the PVI+linear ablation group. There were five adverse events noted, two in the linear group (pericardial effusion not requiring drain) and 3 in the CFAE group (1 pseudoaneurysm, one effusion requiring pericardiocentesis and one effusion nor requiring drain). CONCLUSIONS: Among patients with persistent atrial fibrillation, we found no difference in maintenance of sinus rhythm in either linear ablation or ablation of complex fractionated electrograms was performed in addition to pulmonary vein isolation in short- and long-term follow-up.

Background Brugada syndrome (BrS) is sometimes diagnosed because of chest pain. Prevalence and characteristics of such BrS patients are unknown. Methods A total of 200 BrS probands were retrospectively included. BrS diagnosis made because of chest pain (n = 34, 17%) was compared to the other ones. Results BrS probands with diagnosis because of chest pain had significantly more often smoker habits, increased body mass index, and familial history of coronary artery disease but less frequently previous resuscitated sudden death/syncope or atrial fibrillation. Presence of coronary spasm and familial coronary artery disease were independently associated with BrS diagnosed because of chest pain. They presented more often with spontaneous type 1 ST elevation (59% vs 26%, P = .0004) and higher ST elevation during the episode of chest pain compared to other patients or compared to baseline electrocardiogram after chest pain resumption. ST elevation during chest pain was lower compared to ajmaline test. A total of 20% of them had significant coronary artery disease and four (11%) had coronary spasm, and they experienced more often recurrent chest pain episodes (24% vs 5%, P = .0002). Presence of chest pain at BrS diagnosis was not correlated to future arrhythmic events in univariate analysis. Only previous sudden cardiac death (SD)/syncope and familial SD were still significantly associated with outcome in multivariate analysis. Conclusion Chest pain is a common cause for BrS diagnosis, although major part is not apparently explained by ischemic heart disease. Mechanisms leading to chest main remain unknown in the other ones. ST elevation is higher in this situation but does not seem to carry poor prognosis.

Background:Multipolar catheters are increasingly used for high-density mapping. However, the threshold to define scar areas has not been well described for each configuration. We sought to elucidate the impact of bipolar spacing and orientation on the optimal threshold to match magnetic resonance imaging-defined scar.Method:The HD-Grid catheter uniquely allows for different spatially stable bipolar configurations to be tested. We analyzed the electrograms with settings of HD-16 (3 mm spacing in both along and across bipoles) and HD-32 (1 mm spacing in along bipoles and 3 mm spacing in across bipoles) and determined the optimal cutoff for scar detection in 6 infarcted sheep.Results:From 456 total acquisition sites (mean 76±12 per case), 14 750 points with the HD-16 and 32286 points with the HD-32 configuration for bipolar electrograms were analyzed. For bipolar voltages, the optimal cutoff value to detect the magnetic resonance imaging-defined scar based on the Youden’s Index, and the area under the receiver operating characteristic curve (AUROC) differed depending on the spacing and orientation of bipoles; across 0.84 mV (AUROC, 0.920; 95% CI, 0.911–0.928), along 0.76 mV (AUROC, 0.903; 95% CI, 0.893–0.912), north-east direction 0.95 mV (AUROC, 0.923; 95% CI, 0.913–0.932), and south-east direction, 0.87 mV (AUROC, 0.906; 95% CI, 0.895–0.917) in HD-16; and across 0.83 mV (AUROC, 0.917; 95% CI, 0.911–0.924), along 0.46 mV (AUROC, 0.890; 95% CI, 0.883–0.897), north-east direction 0.89 mV (AUROC, 0.923; 95% CI, 0.917–0.929), and south-east direction 0.83 mV (AUROC, 0.913; 95% CI, 0.906–0.920) in HD-32. Significant differences in AUROC were seen between HD-16 along versus across (P=0.002), HD-16 north-east direction versus south-east direction (P=0.01), HD-32 north-east direction versus south-east direction (PP=0.006). The AUROC was significantly larger (PConclusions:Spacing and orientation of bipoles impacts the accuracy of scar detection. Optimal threshold specific to each bipolar configuration should be determined. Selecting one best voltage point among multiple points projected on the same surface is also critical on the Ensite-system to increase the accuracy of scar-mapping.

Background: Catheter ablation of ventricular tachycardia (VT) in structural heart disease is challenging because of noninducibility or hemodynamic compromise. Ablation often depends on elimination of local abnormal ventricular activities (LAVAs) but which may be hidden in far-field signal. We investigated whether altering activation wavefront affects activation timing and LAVA characterization and allows a better understanding of isthmus anatomy. Methods: Patients with ischemic cardiomyopathy underwent mapping using the ultra-high density Rhythmia system (Boston Scientific). Maps were generated for all stable VTs and with pacing from the atrium, right ventricular apex, and an left ventricular branch of the coronary sinus. Results: Fifty-six paced maps and 23 VT circuits were mapped in 22 patients. In 79% of activation maps, there was ≥1 line of block in the paced conduction wavefront, with 93% having fixed block and 32% showing functional partial block. Bipolar scar was larger with atrial than right ventricular (31.7±18.5 versus 27.6±16.3 cm 2 , P =0.003) or left ventricular pacing (31.7±18.5 versus 27.0±19.2 cm 2 , P =0.009); LAVA areas were smaller with atrial than right ventricular (12.3±10.5 versus 18.4±11.0 cm 2 , P 2 , P 2 , P =0.01). All patients had successful VT isthmus ablation. In 11±8 months follow-up, 2 patients had a recurrence. Conclusions: Wavefronts of conduction slowing/block may aid identification of critical isthmuses in unmappable VTs. Altering the activation wavefront leads to significant differences in conduction properties of myocardial tissue, along with scar and LAVA characterization. In patients where few LAVAs are identified during substrate mapping, using an alternate activation wavefront running perpendicular to the VT isthmus may increase sensitivity to detect arrhythmogenic substrate and critical sites for reentry.

Background The natural history and long‐term outcome in pediatric patients with idiopathic ventricular fibrillation ( IVF ) are poorly characterized. We sought to define the clinical characteristics and long‐term outcomes of a pediatric cohort with an initial diagnosis of IVF . Methods and Results Patients were included from an International Registry of IVF (consisting of 496 patients). Inclusion criteria were: (1) VF with no identifiable cause following comprehensive analysis for ischemic, electrical or structural heart disease and (2) age ≤16 years. These included 54 pediatric IVF cases (age 12.7±3.7 years, 59% male) among whom 28 (52%) had a previous history of syncope (median 2 syncopal episodes [interquartile range 1]). Thirty‐six (67%) had VF in situations associated with high adrenergic tone. During a median 109±12 months of follow‐up, 31 patients (57%) had recurrence of ventricular arrhythmias, mainly VF . Two patients developed phenotypic expression of an inherited arrhythmia syndrome during follow‐up (hypertrophic cardiomyopathy and long QT syndrome, respectively). A total of 15 patients had positive genetic testing for inherited arrhythmia syndromes. Ten patients (18%) experienced device‐related complications. Three patients (6%) died, 2 due to VF storm. Conclusions In pediatric patients with IVF , a minority develop a definite clinical phenotype during long‐term follow‐up. Recurrent VF is common in this patient group.

Objectives This study reports the use of a novel “Lumipoint” algorithm in ventricular tachycardia (VT) ablation. Background Automatic mapping systems aid rapid acquisition of activation maps. However, they may annotate farfield rather than nearfield signal in low voltage areas, making maps difficult to interpret. The Lumipoint algorithm analyzes the complete electrogram tracing and therefore includes nearfield signals in its analysis. Methods Twenty-two patients with ischemic cardiomyopathy and 5 with dilated cardiomyopathy underwent mapping using the ultra-high density Rhythmia system. Lumipoint algorithms were applied retrospectively. Results In all left ventricular substrate maps, changing the window of interest to the post-QRS phase automatically identified late potentials. In 25 of 27 left ventricular VT activation maps, a minimum spatial window of interest correctly identified the VT isthmus as seen by the manually annotated map, entrainment, and response to ablation. In 6 maps, the algorithm identified the isthmus where the standard automatically annotated map did not. Conclusions The Lumipoint algorithm automatically highlights areas with electrograms having specific characteristics or timings. This can identify late and fractionated potentials and regions that exhibit discontinuous activation, as well as the isthmus of a VT circuit. These features may enhance human interpretation of the electrogram signals during a case, particularly where the circuit lies in partial scar with low amplitude nearfield signals and potentially allow a more targeted ablation strategy.

Background Ethanol infusion of the vein of Marshall (VOM) may be effective to treat Marshall bundle-related atrial tachycardia (MB-AT). However, methods and clinical results of ethanol infusion for MB-AT have been not established. Objective To assess the accessibility of the VOM and the success rate of ethanol infusion using a femoral approach for MB-AT. Methods A single-center observational study included consecutive patients who had MB-AT and in whom we attempted to treat MB-AT during AT by ethanol infusion. When the VOM was able to be cannulated following VOM venogram using a femoral approach, we systematically performed ethanol infusion with selective balloon occlusion of the VOM. We analyzed in detail the efficacy of ethanol infusion of VOM in patients who were in MB-AT during ethanol infusion. Results We enrolled 54 consecutive patients in whom we attempted to treat MB-AT by ethanol infusion. Of those, the VOM was accessible in 92.5% of patients (50 of 54). Of the 50 patients treated by ethanol infusion during MB-AT, AT was successfully terminated in 56% percent of the patients (28 of 50) by solo treatment of ethanol infusion without RF ablation. The remainder required additional RF application to terminate the MB-AT. A mean of 6.2 ± 2.8 mL of ethanol was infused resulting in the low-voltage area significantly larger than that before ethanol infusion (12.7 ± 8.3 vs 6.6 ± 5.3 cm2 , P Conclusion The present study demonstrated that the VOM was highly accessible and MB-AT was amenable to treatment by ethanol infusion by using a femoral approach.

Ventricular fibrillation (VF) storm after myocardial infarction (MI) is a life-threatening condition that necessitates multiple defibrillations. Catheter ablation is a potentially effective treatment strategy for VF storm refractory to optimal medical treatment. However, its impact on patient survival has not been verified in a large population.We conducted a multicenter, retrospective observational study involving consecutive patients who underwent catheter ablation of post-MI refractory VF storm without preceding monomorphic ventricular tachycardia. The target of ablation was the Purkinje-related ventricular extrasystoles triggering VF. The primary outcome was in-hospital and long-term mortalities. Univariate logistic regression and Cox proportional-hazards analysis were used to evaluate clinical characteristics associated with in-hospital and long-term mortalities, respectively.One hundred ten patients were enrolled (age, 65±11years; 92 men; left ventricular ejection fraction, 31±10%). VF storm occurred at the acute phase of MI (4.5±2.5 days after the onset of MI during the index hospitalization for MI) in 43 patients (39%), the subacute phase (1 week) in 48 (44%), and the remote phase (6 months) in 19 (17%). The focal triggers were found to originate from the scar border zone in 88 patients (80%). During in-hospital stay after ablation, VF storm subsided in 92 patients (84%). Overall, 30 (27%) in-hospital deaths occurred. The duration from the VF occurrence to the ablation procedure was associated with in-hospital mortality (odds ratio for each 1-day increase, 1.11 [95% CI, 1.03-1.20]; P=0.008). During follow-up after discharge from hospital, only 1 patient developed recurrent VF storm. However, 29 patients (36%) died, with a median survival time of 2.2 years (interquartile range, 1.2-5.5 years). Long-term mortality was associated with left ventricular ejection fraction30% (hazard ratio, 2.54 [95% CI, 1.21-5.32]; P=0.014), New York Heart Association class ≥III (hazard ratio, 2.68 [95% CI, 1.16-6.19]; P=0.021), a history of atrial fibrillation (hazard ratio, 3.89 [95% CI, 1.42-10.67]; P=0.008), and chronic kidney disease (hazard ratio, 2.74 [95% CI, 1.15-6.49]; P=0.023).In patients with MI presenting with focally triggered VF storm, catheter ablation of culprit triggers is lifesaving and appears to be associated with short- and long-term freedom from recurrent VF storm. Mortality over the long-term follow-up is associated with the severity of underlying cardiovascular disease and comorbidities in this specific patient population.

International audience; ObjectiveThis study sought to determine whether 3-dimensionally-reconstructed computed tomography (CT) channels correlate with electrophysiological isthmuses during ventricular tachycardia (VT).MethodsWe retrospectively studied 9 postinfarction patients (aged 57 ± 15 years, 1 female) with 10 complete VT activation maps (cycle length 429 ± 77ms) created using high-resolution mapping. Three-dimensionally-reconstructed WT maps from CT were merged with the activation map during sinus rhythm (SR) and VT. The relationship between WT and electrophysiological characteristics was analyzed.ResultsA total of 41 CT channels were identified (median 4 per patient), of median (range) length 21.2 mm (17.3–36.8 mm), width 9.0 mm (6.7–16.5 mm), and area 1.49 cm2(1.00–1.75 cm2). WT in the channel was significantly thicker in the center than in the edge (median 2.4 mm vs 1.5 mm, P < .0001). Of 3163 (2493–5960) mapping points in SR, 382 (191–1115) local abnormal ventricular activities (LAVAs) were identified. One patient had a maximal proportion of LAVAs in 3–4 mm, 3 patients in 2–3 mm, 2 in 1–2 mm, and 2 in 0–1 mm. The VT isthmuses of all 10 VTs corresponded with 1–4 CT channels. Twenty-one of the 41 CT channels (51.2%) corresponded to a VT isthmus (entrance, mid, or exit). Electrophysiological VT isthmuses were more likely to be associated with CT channels that were longer (P = .04, odds ratio [OR] 1.05/mm), thinner (but not less than 1 mm) (P = .03, OR 0.36/mm), or parallel to the mitral annulus (P = .07, OR 3.93).ConclusionVT isthmuses were always found in CT channels (100% sensitivity), and half of CT channels hosted VT isthmuses (PPV 51%). Longer and thinner (but >1 mm) CT channels were significantly associated with VT isthmuses.