Arrhythmogenic Foci Research Articles

A Comprehensive Review on Stereotactic Arrhythmia Radioablation (STAR): Pioneering a New Era in Arrhythmia Management.

Stereotactic arrhythmia radioablation (STAR) is an innovative treatment modality that leverages advanced imaging techniques and focused radiation to target arrhythmogenic foci within the heart, offering a non-invasive alternative to traditional catheter ablation methods. Arrhythmias, characterized by irregular heartbeats, pose significant health risks, including heart failure and stroke, particularly among older adults. Traditional management approaches, such as pharmacological therapies and catheter ablation, often face efficacy, safety, and recurrence limitations. STAR addresses these challenges by utilizing high-precision stereotactic technology to deliver targeted radiation, minimizing damage to surrounding tissues while maximizing therapeutic effects. This review explores the mechanisms, clinical indications, procedural techniques, and outcomes associated with STAR. Recent clinical studies demonstrate that STAR provides comparable efficacy to catheter ablation, with a favorable safety profile, making it a promising option for patients who have not responded to conventional treatments. Integrating STAR into arrhythmia management protocols may enhance patient outcomes and reduce the burden of recurrent arrhythmias. As research in this field advances, STAR holds the potential to reshape the landscape of arrhythmia treatment, providing new hope for patients suffering from these complex conditions. This review aims to elucidate the significance of STAR in modern arrhythmia management and to encourage further exploration and clinical application of this pioneering technique.

Implementing stereotactic arrhythmia radioablation with STOPSTORM.eu consortium support: intermediate results of aprospective Israeli single-institutional trial.

Ventricular tachycardia (VT) is alife-threatening arrhythmia originating from the heart's ventricles. Traditional treatments include antiarrhythmic medications, implantable cardioverter-defibrillators (ICDs), and catheter ablation. Stereotactic body radiation therapy (SBRT) targeting the arrhythmogenic focus in the left ventricle-stereotactic arrhythmia radioablation (STAR)-is an emerging treatment and may offer apotential solution for patients with refractory VT. We designed an interventional prospective clinical trial in Israel aligned with the STOPSTORM.eu consortium's benchmarks, recommendations, and directives to assess the safety and efficacy of STAR in patients with refractory VT. Our phaseI/II single-institutional trial was approved by the Ministry of Health of Israel for 10patients, initially assessing safety in the first 3patients. We included patients with ICDs experiencing symptomatic monomorphic VT after an inadequate response to previous therapies. The primary endpoints were treatment-related serious adverse events and areduction in VT burden as assessed by ICD interrogation. Secondary outcomes included areduction in antiarrhythmic medications and changes in quality of life. From August 2023 to August 2024, 3patients underwent STAR treatment. The prescription dose was asingle fraction of 25 Gy. Planning target volumes were 47.8, 49.7, and 91.8 cc, and treatment was successfully delivered with no grade3 or higher adverse events reported. Over afollow-up period of 12months for the first patient and 8months for the second one, no VT events were recorded after treatment. The third patient died from progressive heart failure 3months after treatment. Left ventricular ejection fraction remained stable, and no significant radiation-induced inflammatory changes were noted. The initial results of this trial suggest that STAR can reduce VT episodes in patients with refractory VT without severe adverse effects. The study highlights the importance of international collaboration and standardization in pioneering new treatments. Further follow-up and additional patient data will be necessary to confirm these findings and evaluate long-term outcomes, including potential adjustments to antiarrhythmic medication regimens.

Management of Left Atrial Tachyrhythms in the Setting of HFpEF with Pulsed-Field Ablation: Treating Fire with Water?

Atrial fibrillation (AF) in the setting of heart failure (HF) with preserved ejection fraction (HFpEF) is a prevalent comorbidity and is enabled by adverse left atrial (LA) remodeling, dilation, and scar tissue formation. These changes are facilitated by poor left ventricular compliance. A growing body of clinical evidence and medical guidelines suggest that managing atrial tachyrhythms with catheter ablation (CA) is paramount to treating concomitant HF. This recommendation is complicated in that thermal CA modalities, namely radiofrequency ablation and cryoablation, are both therapeutic via inducing additional scar tissue. AF treatment with thermal CA may compound the atrial scar burden for patients who already have extensive scars secondary to HFpEF. Therefore, thermal CA could act as "gasoline" to the slowly burning "fire" within the LA, increasing the rate of AF recurrence. Pulsed-field ablation (PFA), which utilizes high-voltage irreversible electroporation, is a non-thermal CA technique that is capable of disrupting reentrant microcircuits and arrhythmogenic foci without inducing significant scar burden. PFA has the potential to mitigate the strong fibrosis response to thermal CA that predisposes to AF by serving as "water" rather than "gasoline". Thus, PFA may increase the efficacy and durability of CA for AF in HFpEF, and subsequently, may decrease the risk of procedural complications from repeat CAs. In this article, we provide a summary of the clinical concepts underlying HFpEF and AF and then summarize the data to date on the potential of PFA being a superior CA technique for AF in the setting of comorbid HFpEF.

Association of superior vena cava isolation with improved outcomes in atrial fibrillation ablation

Abstract Background Pulmonary vein isolation (PVI) is the mainstay in atrial fibrillation (AF) ablation. However, additional arrhythmogenic foci seem to contribute to AF initiation and maintenance. A great proportion of those non-PV foci have been reported to be located in the superior vena cava. Purpose We aimed to investigate the effectiveness of SVC isolation as an adjunctive therapy to PVI isolation. Methods We performed a systematic review of MEDLINE, CENTRAL, and Embase. Inclusion criteria were cohort studies with control group or randomized clinical trials, comparing patients undergoing PVI only and patients undergoing PVI with concurrent SVC isolation, in effects of freedom from atrial tachycardia, need for cardioversion, hospitalization and all-cause mortality. Results A total of 7 studies, incorporating 1.550 patients, were included. The combination of SVC and PVI isolation in patients undergoing AF ablation was more effective than PVI isolation alone (risk ratio = 0.689; 95% confidence interval, 0.505-0.942). In a subgroup analysis, the isolation of SVC after identifying focal potentials demonstrated effectiveness (risk ratio = 0.573; 95% confidence interval, 0.364-0.902), while the isolation of SVC when the focal potentials were induced after isoprotenerol infusion or rapid atrial pacing did not alter the clinical outcomes (risk ratio = 0.798; 95% confidence interval, 0.493, 1.292). Conclusions The outcomes of AF ablation are favorable when additional SVC isolation is conducted. The effect is pronounced when spontaneous SVC potentials are identified.

Signal-averaged electrocardiography as a noninvasive tool for evaluating the ventricular substrate in patients with nonischemic cardiomyopathy: reassessment of an old tool.

Signal-averaged electrocardiography (SAECG) provides diagnostic and prognostic information regarding cardiac diseases. However, its value in other nonischemic cardiomyopathies (NICMs) remains unclear. This study aimed to investigate the role of SAECG in patients with NICM. This retrospective study included consecutive patients with NICM who underwent SAECG, biventricular substrate mapping, and ablation for ventricular arrhythmia (VA). Patients with baseline ventricular conduction disturbances were excluded. Patients who fulfilled at least one SAECG criterion were categorized into Group 1, and the other patients were categorized into Group 2. Baseline and ventricular substrate characteristics were compared between the two groups. The study included 58 patients (39 men, mean age 50.4 ± 15.5 years), with 34 and 24 patients in Groups 1 and 2, respectively. Epicardial mapping was performed in eight (23.5%) and six patients (25.0%) in Groups 1 and 2 (p = 0.897), respectively. Patients in Group 1 had a more extensive right ventricular (RV) low-voltage zone (LVZ) and scar area than those in Group 2. Group 1 had a larger epicardial LVZ than Group 2. Epicardial late potentials were more frequent in Group 1 than in Group 2. There were more arrhythmogenic foci within the RV outflow tract in Group 1 than in Group 2. There was no significant difference in long-term VA recurrence. In our NICM population, a positive SAECG was associated with a larger RV endocardial scar, epicardial scar/late potentials, and a higher incidence of arrhythmogenic foci in the RV outflow tract.

Electrical Injury-induced Atrial Fibrillation

Atrial fibrillation (AF) is a prevalent cardiac arrhythmia with significant morbidity and mortality risks. Electrical shocks can elicit adverse cardiac effects, including arrhythmias, although AF following electrical injuries remains relatively rare. We present the case of a 45-year-old man who developed AF after accidentally touching a live cable carrying 220 volts during home construction. The patient exhibited palpitations and shortness of breath and was admitted to the emergency department. Electrocardiographic monitoring confirmed AF with an irregular heart rate of 106 bpm. Echocardiographic examination revealed AF with normal ejection fraction. Successful pharmacological cardioversion using digoxin restored normal sinus rhythm within 6 h. The mechanisms underlying AF after electrical injury are not fully understood, but they likely involve arrhythmogenic foci formation and alterations in cardiac ion channels. Prompt diagnosis and management are crucial, with digoxin proving effective in this case. AF is a rare but clinically significant occurrence following low-voltage electrical shocks. Early diagnosis and appropriate management are essential in resolving the arrhythmia and optimizing patient outcomes. Further research is needed to understand the mechanisms and risk factors associated with this rare occurrence and explore long-term outcomes and potential complications.

Myocardial electroporation — an alternative to thermal methods of atrial fibrillation treatment

Atrial fibrillation is one of the most common cardiac arrhythmias. By all estimates, the number of patients with this arrhythmia will only increase. Currently, the main and most used methods for the treatment of atrial fibrillation are radiofrequency and cryo-balloon ablation. However, the accumulated experience of their use has revealed a number of shortcomings — the lack of long-term pulmonary vein isolation, as well as life-threatening procedure complications. Relatively recent foreign studies showed data on the use of an alternative method of influencing arrhythmogenic foci. The method is based on the use of non-thermal pulsed field ablation, which leads to the appearance of pores in cardiomyocytes and their necrosis, which causes a more stable electrical left atrial pulmonary vein isolation. The margins of the lesions in this exposure are usually very sharp with a narrow transition from normal tissue to tissue with the complete necrosis, while not damaging neighboring structures such as blood vessels, nerves and esophagus. At present, information published in the literature on the use of pulsed field ablation in various fields of medicine, including oncology and cardiology, is clearly not enough. The implementation of this method for the interventional treatment of cardiac arrhythmias is considered a promising direction and is the subject of research by many leading scientific groups around the world. The purpose of this review is to structure the most significant information on the use of pulsed field ablation, presented in the literature, to analyze its possibilities, effectiveness, and disadvantages.

"<i>Primum non nocere</i> (First, do no harm)". Case report

Diastolic myocardial dysfunction is the most important pathogenetic factor in heart failure and makes a significant contribution to hemodynamic disorders, which leads to a significant deterioration in the quality of life and prognosis of patients. This article presents a case of a patient with hypertrophic cardiomyopathy with paroxysmal atrial fibrillation and repeated pulmonary edema due to impaired diastolic function, a significant increase in mitral regurgitation and pulmonary hypertension. Given the ineffectiveness of antiarrhythmic therapy and the predicted failure of catheter ablation of the arrhythmogenic focus, the patient was scheduled for atrioventricular destruction. However, the strategy was revised to optimize the heart failure therapy, against which the tachysystole paroxysmal atrial fibrillation did not recur over the following time.

Is it possible to determine arrhythmogenic focus localization of ventricular ectopic complexes detected by ambulatory electrocardiogram monitoring?

Aim. To study the possibility of using algorithms (developed using resting ECG as a mapping tool) for localization arrhythmogenic focus of ventricular arrhythmias (VA) detected by ambulatory 12-lead ECG monitoring (AECGM) with the identification of predominant origins of VA.Material and methods. The study included 54 patients aged 45 to 80 years with high frequency VA evaluated during AECGM: 29 — with coronary artery disease (CAD), 25 — w ithout CAD, who underwent radiofrequency ablation (RFA). The study included patients with effective ablation based on AECGM performed 6 months after RFA. Verification localization of VA exit site was carried out during endocardial mapping and AECGM («Cardiotechnika-04, СT-07», «Incart»). The following algorithms were considered in the study: D. Kuchar; O. Segal; J. Miller; A. S. Revishvili, R. Y. Snegur (2006, 2007); A. B. Weinstein; M. V. Noskova. It was assessed the percentage of matches applying the comparative analysis of results of the invasive and non-invasive methods, and it was revealed the predominant localization of VA.Results. The following algorithms had the highest percentage of matches: D. Kuchar in patients with CAD; A. S. Revishvili, R. Y. Snegur (2007) and M. V. Noskova in patients without CAD. The predominant origins of VA in patients without CAD were the left sinus of Valsalva, right ventricular outflow tract, and in patients with CAD — b asal inferior left ventricular wall, right ventricular outflow tract.Conclusion. Algorithms for arrhythmogenic focus localization of VA, developed using resting ECG, can be used to determine the origin of VA detecting by 12-lead AECGM, taking into account patient’s medical history (CAD, myocardial infarction).

213: ONE SHOCK TREATED WITH ANOTHER: NEW-ONSET ATRIAL FIBRILLATION AFTER HIGH-VOLTAGE ELECTRICAL INJURY

Introduction: Development of atrial fibrillation following electrical injury has been rarely reported in literature. This can place medical providers in a situation where they are uncertain on how to manage such event. We present a case of high voltage electrical injury (7200V) resulting in new onset atrial fibrillation. Description: A 38-year-old electric line worker with no previous medical history came in with complaint of new onset palpitations and lightheadedness that started an hour prior to arrival. Patient stated he was standing on a boom lift, pressure-washing a church’s tower when his lance touched an electrical wire overhead. The lines were coming from a main electric pole estimated to be 7200V that connected to the transformer. Patient felt a shock pass through his right hand down to the rest of his body for a few seconds, and then he fell. He was not wearing any gloves. He denied any loss of consciousness, alcohol use, chest pain or any previous heart condition. In the ED, he was found to be in atrial fibrillation with heart rate ranging from 110-150. His CPK was 295 units/L and troponin was < 6 ng/L. Patient received IV diltiazem 15mg and IV amiodarone 150mg. He was started on amiodarone drip, admitted to ICU for monitoring and transitioned to Metoprolol 25mg BID and Xarelto 15mg daily the next day before discharge. Three weeks later, he underwent transesophageal echocardiogram (TEE) guided electrical cardioversion for persistent atrial fibrillation. Discussion: Electrical injury can induce cardiac arrhythmias via different mechanisms. The sheer energy of the electric current could directly stimulate the myocytes. It could also impair the sodium-potassium adenosine triphosphatase transporter which plays a major role in electrical-mechanical activity of cardiac muscle. Myocardial necrosis can also lead to production of new arrhythmogenic foci. Troponin and CPK are not always strong indicators of myocardial injury, however, high CK levels >400 units/L may be associated with longer hospitalization, and a greater risk of skin grafting or amputation. Atrial fibrillation in setting of electrical injury is managed with the use of beta blockers, anti-arrhythmics and in some cases, electrical cardioversion.

Abstract 14225: Atrial Tachycardias After Surgical Left Atrial Appendage Exclusion

Introduction: Surgical left atrial appendage exclusion (LAA-Ex) is often performed to eliminate the need for long-term anticoagulation either as a stand-alone or concomitant procedure during cardiac surgery. A modified MAZE procedure is also usually performed during surgical LAA-Ex. Residual arrhythmogenic foci within the LAAA and/or zones of slow conduction along the stump of the LAA may contribute to recurrent atrial tachycardias (AT) after LAA-Ex. The purpose of this study was to determine the role of the LAA in recurrent atrial tachycardias (ATs) after surgical LAA-Ex. Methods: Catheter ablation (CA) was performed to eliminate ATs in 21 patients with history of AF (persistent in 18/21, 86%) 25±26 months after surgical LAA-Ex. There were 3 women; mean age was 66±9 years; and the left atrial diameter was 54±8 mms. A concomitant MAZE procedure and CA was performed previously, in 16 and 9 patients, respectively. Two patients had neither maze nor catheter ablation. There was residual blood flow into the LAA in 1/21 patient. Results: A reentrant AT involving the stump of the LAA was identified in 5/21 (24%) patients. Focal ablation on a critical isthmus within a zone of slow conduction along the LAA stump terminated AT in 3/5 patients. In the remaining 2 patients a linear lesion set from the stump to an existing line of block (left atrial roof line and anterior mitral annulus) terminated the macroreentrant AT revolving around the LAA stump. During 16±13 months of follow-up 10/21 patients (48%) remained free from recurrent ATs without antiarrhythmic drug therapy. A repeat ablation was performed in 3 patients, the mechanism of the AT was epicardial, perimitral, and multifocal but did not involve the LAA. Conclusions: After surgical LAA-Ex recurrent ATs are not uncommon and can involve the LAA stump, Although these ATs can be successfully identified and ablated, other ATs may recur and prompt additional antiarrhythmic or ablative therapy.

Comparison of pulmonary veins in patients with and without atrial fibrillation using multidedector computed tomographic angiography

Objectives: Atrial fibrilation (AF) develops from an arrhythmogenic ectopic focus, which triggers the vicious circle that creates arrhythmias. Arrhythmogenic foci are often located in the transition areas between the pulmonary veins and the left atrial endothelium. This study aims to compare the pulmonary vein anatomy of patients with and without AF using multidetector computed tomographic (MDCT) angiography and to evaluate the relationship between the presence of pulmonary vein variations and the development of AF. Methods: Seventy cases (38 males, 32 females) aged between 23 and 75 (mean age: 49.9 ± 13.3 years) were included in this study. This study consisted of 20 patients undergoing endovascular radiofrequency catheter ablation with AF and 50 participants (control) without AF. MDCT angiography examination was performed for the evaluation of pulmonary vein anatomy and variations. Results: Normal pulmonary vein anatomy was observed in 30% (n = 6) of the study group, 60% (n = 30) of the control group, and 51.4% (n = 36) of the total of both groups. Variation in pulmonary vein anatomy (accessory pulmonary vein or common ostium) was detected in 48.6% (n = 34/70) of the cases. The most common variation was the presence of accessory pulmonary vein (35.7%). Common ostium was found to be the second most common variation (12.8%). All common ostia were localized on the left side. Early branching of pulmonary veins was detected in 41 (58.5%) of 70 cases. Conclusions: Accesory pulmonary vein, common ostium and early branching are more frequently present in patients with AF.

Ethanol Infusion of Vein of Marshall for the Treatment of Persistent Atrial Fibrillation: The Basics and Clinical Practice.

Catheter ablation for persistent atrial fibrillation (PeAF) is particularly challenging, as the clinical outcomes are modest. Pulmonary vein isolation (PVI) plus linear ablation is one of the main strategies for PeAF ablation. Completely durable transmural lesions are difficult to achieve by catheter ablation during mitral isthmus ablation. The ligament of Marshall contains the vein of Marshall (VOM), myocardial tracts and innervation, and serves as arrhythmogenic foci that make it an attractive target in catheter ablation of atrial fibrillation. Additionally, it co-localizes with the mitral isthmus, and may serve as a part of the perimitral isthmus reentrant circuit. Ethanol infusion into the VOM results in rapid ablation of the neighboring myocardium and its innervation. Its incorporation into PVI significantly increases the success rate of mitral isthmus block and the clinical outcome of PeAF ablation.

Inferior Vena Cava as a Trigger for Paroxysmal Atrial Fibrillation: Incidence, Characteristics, and Implications.

Identifying nonpulmonary vein triggers during atrial fibrillation (AF) ablation is of great importance. Currently, there are limited data on AF triggered by the inferior vena cava (IVC). This study was performed to investigate the incidence, characteristics, and implications of IVC triggers for AF. A total of 661 patients who underwent initial paroxysmal AF ablation were included. After pulmonary vein isolation, ectopic beats that triggered AF were further studied. Activation mapping and angiography were performed to confirm the location of ectopic origin. Electrocardiographic analysis of the ectopic P-wave (P'-wave) was performed. Six patients (0.91%) with AF triggered by the IVC were confirmed. The mean distance from the earliest activation site to the IVC ostium was 6.8 ± 2.5mm (5.2 to 11.2mm). Furthermore, the arrhythmogenic foci within the IVCwere all located at the apical hemisphere of the IVC (3 at the septal side and 3 at the anterior side). A total of 2.3±0.5 applications of radiofrequency energy were delivered to eliminate IVC triggers. The mean duration of the P'wave was 91.2 ± 11.2 milliseconds (81 to 108 milliseconds), which was narrower than that of the sinus P-wave (115.2±19.3 milliseconds [87 to 139 milliseconds]; P = 0.002). Moreover, the configuration of all P' waves in the inferior leads was negative. During a mean follow-up period of 25.5 ± 7.3months, all 6 patients remained arrhythmia free without antiarrhythmic drugs. IVC trigger, a rare but latent source of paroxysmal AF, could be identified and safely eliminated by focal radiofrequency ablation. Ectopic beats originating from the IVC presented with narrow P'-wave duration and negative P'waves in all inferior leads.

SUCCESSFUL ABLATION IN PEDIATRIC PATIENT WITH SURGICAL REPAIR OF RASTELLI AV CANAL TYPE SECUNDARY TO REFRACTORY VENTRICULAR TACHYCARDIA

TYPE: Late Breaking Case Report TOPIC: Critical Care INTRODUCTION: The management of the patient with post surgical cardiac pathology is complex, frecuently requiring critical care and multidisciplinary interventions to have success. We present a complicated clinical case with complicated ventircular tachycardia treated with ablation of the ventricular arrhythmogenic focus. CASE PRESENTATION: 5-Year-old female with down syndrome and rastelli type “A” av channel weight 18 kg. It is admitted in picu for corrective repair, presenting as a complication of refractory ventricular tachycardia under medical management. With post-surgical echocardiogram without residual defects, lvef of 79%. Extubed in its first 48 post-surgical hours, shows collapse rhythm, beginning amiodarone, lidocaine and even electric cardioversion, ventilatory support and vasoactive without improvement. Cardiac and myocardial profile: troponin i: 300 ckmb: 24 myoglobin: 311, probnp: 2501. ecg: monomorphic ventricular fibrillation, abnormal axis deviation, incomplete right branch block, right ventricular hypetrophy. Undergo catheterism with ablation of arrhythmogenic focus in anterior lateral wall of the left ventricle. DISCUSSION: Transcathether ablation by radio frequency constitutes a curative therapeutic alternative for different cardiac tachyarrhythmias already proven in pediatric patients, it has demonstrated a high effectiveness of the problem resolution. CONCLUSIONS: Radiofrequency ablation is an excellent therapeutic tool in critical medicine for surgical complications such as ventricular tachycardia refractria with ventricular arrithmogenic focus. DISCLOSURE: Nothing to declare. KEYWORD: refractory ventricular tachycardia

Back to the Future.

I was asked to describe the left atrial anatomy in Mr Smith, an elderly gentleman with atrial fibrillation, whose cardiologist needed a CT to plan the ablation of a potentially arrhythmogenic foci in the pulmonary veins. Despite the complexity of the procedure, the questions for me were simple: How many veins? How big are the veins? Any tributaries within 10 mm of the vein joining the left atrium? My report would then be copied and pasted into the cardiologist’s summary of the patient under the heading “Data.”

Evaluation of arrhythmogenic foci using a novel automated detection algorithm and isoproterenol in persistent atrial fibrillation

The CARTOFINDER mapping system analyzes activation patterns using unipolar potentials during atrial fibrillation (AF), where isoproterenol (ISP) is conventionally used to induce non-pulmonary vein (PV) foci and confirm PV arrhythmogenicity. In 20 patients with persistent AF who underwent ablation at our hospital, arrhythmogenic foci were evaluated using both these methods. Before pulmonary vein isolation (PVI), PV and left atrium (LA) were analyzed during AF using CARTOFINDER, and the isolation line was determined based on the results. After PVI, ISP was loaded after return of sinus rhythm and confirmation of the presence of arrhythmogenic foci. The activation site in LA was ablated at the discretion of the surgeon. Focal activation sites detected by CARTOFINDER correlated with the arrhythmogenic foci induced by ISP in the PVs. The results also showed that a greater number of focal activation sites in the PVs correlated to an increased response to ISP administration. In one patient, it was observed that the focal activation site identified in the PV also coincided with the site of the origin of automaticity induced by ISP after PVI. CARTOFINDER and ISP both reliably determined the presence of arrhythmogenic foci in PV, in patients with persistent AF. Knowledge of the nature of arrhythmogenic foci in non-PV is considered to be a topic for future studies, and further data collection is required.

New safe approach to target symptomatic Hisian ectopy/tachycardia

Although cryoenergy safety profile is appropriate for the ablation of arrhythmogenic foci near the conduction system, mapping using the cryoablation catheter is of limited precision. Combining the safety of cryoenergy and the high precision of a 3D mapping system therefore appears the most appropriate set-up for ablation in the vicinity of the His bundle. A 29-year-old woman with a 3-year history of increasing shorteness of breath and palpitations refractory to medical treatment was sent to the EP laboratory for catheter ablation. Surface ECG showed sinus rhythm and frequent ectopic beats with narrow QRS complexes similar to those of the sinus beats. The left ventricular ejection fraction was impaired (38%) with no other etiology found, apart from frequent ectopies. Detailed intracardiac mapping, using a 3D electroanatomical system, revealed that the ectopy originated from the distal His bundle, which was indicated by both antegrade and reversed His bundle activation sequence during ectopy compared to that during sinus rhythm. Due to the proximity of the conduction system, cryoenergy rather than radiofrequency was chosen to target this Hisian ectopy. A special set-up was made in order to allow the cryoablation catheter to be visualized into the 3D mapping system. Cryoenergy delivered to the site of earliest Hisian ectopy activation completely abolished it ( Fig. 1 ). Such a combined approach may help to improve therapeutic strategy for ablation procedures with a high-risk of injury to the conduction system. It could notably be extended to the ablation of para-Hisian ectopy or accessory pathways.

Identification of novel pulmonary vein nodes as generators of ectopic arrhythmic foci for atrial fibrillation: an immunohistochemical proof.

The atrial muscle sleeve (AMS) of the pulmonary vein is the most common source of the arrhythmogenic triggers in atrial fibrillation (AF). Anatomical substrate generating these ectopic currents is still elusive. The present study was designed to study the AMS of pulmonary veins with an emphasis on the structural basis which might govern AF initiation and perpetuation. The study was conducted on a longitudinal tissue section of pulmonary vein, taken from 15 human cadaveric nondiseased hearts. Tissue was studied histologically using H&E and Gömöri trichrome stain. The pacemaker channels were identified by immunohistochemistry using monoclonal HCN4 and HCN1 antibodies. The AMS was identified in each pulmonary vein, located between the tunica adventitia and tunica media. A node-like arrangement of myocytes was seen within the AMS in 30% of veins. It had a compact zone limited by a fibrous capsule and contained much smaller, paler and interconnected myocytes. Outside the capsule, there was a zone of dispersed, singly placed myocytes separating the compact zone from the working myocytes of the AMS. HCN4 and HCN1 antibodies were expressed on the cell membrane of nodal myocytes, while the working myocytes demonstrated none to minimal staining. Pulmonary veins nodes are similar to the specialized cardiac conductive tissue in the histological arrangement of compact and transitional zones, cellular characteristics and the presence of pacemaker channels. They might be the anatomical basis of ectopic arrhythmogenic foci. To our knowledge, these nodes are being described for the first time in human.

Clinical and functional characteristics of children with ventricular arrhythmias depending on the ectopic focus localization

Aim. To determine the prevalence of ventricular arrhythmias (VA) among children with cardiac arrhythmias and to assess the clinical, functional, and electrophysiological characteristics of VA, depending on the localization of the ectopic focus.Methods. The study included 260 children, 153 (58,8%) boys, the mean age of patients was 13.4±3.1years. Based on clinical and anamnestic data, ECG, Holter monitoring, echocardiography, dosed exercise test, invasive electrophysiological study (EPS), radiofrequency ablation (RFA) a comparative assessment of the clinical and functional features of the most frequently diagnosed localizations of the ectopic focus in children with VA was carried out according to the data of invasive EPS, RFA.Results. According to invasive EPI, the most frequent localization of VA in children is the right ventricle outflow tract (RVOT) - 144 (55%), less often - the Valsalva sinuses - 52 (20%) and the RV free wall - 47 (18%). In most cases (255 children, 98%) there was a focal arrhythmia (trigger activity). The localization of ectopia in the RV free wall is characterized by the predominance of single ventricular premature beats (VPB) or in combination with a paired VPB (78,7%) and polymorphism of ventricular complexes (30%). The peculiarity of ventricular tachycardia in this localization is its stable character (17,0%) and low heart rate in volleys (idioventricular rhythm) (12,8%). When the focus was localized in the RVOT, as well as when it was localized in the RV free wall, single VPB or in combination with paired VPB prevailed (84,7%), but polymorphism of ventricular complexes was less often observed (10,4%). Differences in myocardial contractility at the sinus rhythm in right ventricular arrhythmias were revealed. Thus, the ejection fraction at the localization of the lesion in the RV free wall was significantly lower than in the RVOT (63.4±5.5% and 65.8±5.9%, respectively; p&lt;0.01). Hemodynamic significance is characteristic for RV arrhythmias (21.3% and 16.0% of patients) and was practically not observed at the left-sided localization of the arrhythmogenic focus (3.8%; p&lt;0.01). VA in patients without structural heart disease, regardless of the localization of the arrhythmic focus in children, is asymptomatic and is detected, in most cases, within the framework of clinical examination 206 patients, 79.2%. The prevalence of syncope in children with idiopathic VA is 15.8% (41 patients), and in most cases, they are of vaso-vagal origin. In most children (178, 70%), idiopathic VA is dependent on the level of parasympathetic influences on the heart, disappearing or significantly decreasing during exercise, which is revealed during the stress test confirming the high role of autonomic influences on the regulation of heterotopic rhythm in children with VA.Conclusion. VA is a common arrhythmia in children. Depending on the localization of the arrhythmogenic focus, characteristic features of the structure and density of the heart, as well as differences in the contractile function of the myocardium on the sinus rhythm and on the ectopic complex were revealed.