Substrate For Arrhythmias Research Articles

PO-683-07 CARDIOVASCULAR MAGNETIC RESONANCE MYOCARDIAL SCAR PATTERN PREDICTS MAJOR CARDIOVASCULAR EVENTS IN CORONARY ARTERY DISEASE

Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) is a powerful tool in the evaluation of myocardial scar, a known substrate for ventricular cardiac arrhythmia. Disparity in scar microstructure may drive important arrhythmogenic mechanisms. Analysis of these regions offers the potential for novel, non-invasive, risk stratification approaches for patients with coronary artery disease (CAD).

Bi-atrial characterization of the electrical substrate in patients with atrial fibrillation.

BackgroundLittle is known regarding the characterization of electrical substrate in both atria in patients with atrial fibrillation (AF).MethodsEight consecutive patients undergoing AF ablation (five paroxysmal, three persistent) underwent electrical substrate characterization during sinus rhythm. Mapping of the left (LA) and right atrium (RA) was performed with the use of the HD Grid catheter (Abbott). Bipolar voltage maps were analyzed to search for low voltage areas (LVA), the following electrophysiological phenomena were assessed: (1) slow conduction corridors, and (2) lines of block. EGMs were characterized to search for fractionation. Electrical characteristics were compared between atria and between paroxysmal versus persistent AF patients.ResultsIn the RA, LVAs were present in 60% of patients with paroxysmal AF and 100% of patients with persistent AF. In the LA, LVAs were present in 40% of patients with paroxysmal AF and 66% of patients with persistent AF. The areas of LVA in the RA and LA were 4.8±7.3 cm2 and 7.8±13.6 cm2 in patients with paroxysmal AF versus 11.7±3.0 cm2 and 2.1±1.8 cm2 in patients with persistent AF. In the RA, slow conduction corridors were present in 40.0% (paroxysmal AF) versus 66.7% (persistent AF) whereas in the LA, slow conduction corridors occurred in 20.0% versus 33.3% respectively (p = ns). EGM analysis showed more fractionation in persistent AF patients than paroxysmal (RA: persistent AF 10.8 vs. paroxysmal AF 4.7%, p = .036, LA: 10.3 vs. 4.1%, p = .108).ConclusionBi‐atrial involvement is present in patients with paroxysmal and persistent AF. This is expressed by low voltage areas and slow conduction corridors whose extension progresses as the arrhythmia becomes persistent. This electrophysiological substrate demonstrates the important interplay with the pulmonary vein triggers to constitute the substrate for persistent arrhythmia.

Radiosurgery in Treatment of Ventricular Tachycardia – Initial Experience Within the Polish SMART-VT Trial

BackgroundStereotactic Arrhythmia Radioablation (STAR) is an emerging treatment modality for patients with sustained ventricular tachycardia (VT) and refractory to treatment with drugs and radiofrequency catheter ablation (RFA). It is believed that up to 12–17% of patients experience recurrence of VT within 1 year of follow-up; thus, novel therapeutic options are needed. The aim of this article is to present initial experience within a novel treatment modality for VT.Case SummaryTwo patients with a medical history of coronary artery disease and heart failure with reduced left ventricle (LV) ejection fraction, after implantation of cardioverter-defibrillator (ICD) and previous unsuccessful RFAs owing to sustained VT were admitted to the cardiology department due to recurrence of sustained VT episodes. With electroanatomical mapping (EAM), the VT substrate in LV has been confirmed and specified. In order to determine the target volume for radioablation, contrast-enhanced computed tomography was performed and the arrhythmia substrate was contoured using EAM data. Using the Volumetric Modulated Arc Therapy technique and three 6 MeV flattening filter-free photon beam fields, a single dose of 25 Gy was delivered to the target volume structure located in the apex and anterior apical segments of LV in the first patient and in the apex, anterolateral and inferior apical segments of the second patient. In both cases, volumes of the target structures were comparable. Interrogation of the implanted ICD at follow-up visits throughout 6 months after the treatment revealed no VT episodes in the first patient and sudden periprocedural increase in VT burden with a subsequent gradual decrease of ventricular arrhythmia to only two non-sustained episodes at the end of the follow-up period in case of the second patient. A significant reduction in premature ventricular contractions burden was observed compared to the pre-treatment period. No noticeable deterioration in LV function was noted, nor any adverse effects of radiosurgery associated with the implanted device.ConclusionThe early response to STAR can be unpredictable and probably does not reflect the final outcome of irradiation. Close monitoring of patients, especially in the early period after irradiation is crucial to properly handle potentially harmful early reactions to STAR.

Recent Insights Into Mechanisms and Clinical Approaches to Electrical Storm.

Electrical storm, characterized by repetitive ventricular tachycardia/ventricular fibrillation over a short period, is becoming more common with widespread use of implantable cardioverter defibrillator (ICD) therapy. Electrical storm, sometimes called "arrhythmic storm" or "ventricular tachycardia storm," is usually a medical emergency requiring hospitalization and expert management, and significantly affects short- and long-term outcomes. This syndrome typically occurs in patients with underlying structural heart disease (ischemic or nonischemic cardiomyopathy) or inherited channelopathies. Triggers for electrical storm should be sought but are often unidentifiable. Initial management is dictated by the hemodynamic status, whereas subsequent management typically involves ICD interrogation and reprogramming to reduce recurrent shocks, identification and management of triggers like electrolyte abnormalities, myocardial ischemia, or decompensated heart failure, and antiarrhythmic drug therapy or catheter ablation. Sympathetic nervous system activation is central to the initiation and maintenance of arrhythmic storm, so autonomic modulation is a cornerstone of management. Sympathetic inhibition can be achieved with medications (particularly β-adrenoreceptor blockers), deep sedation, or cardiac sympathetic denervation. More definitive management targets the underlying ventricular arrhythmia substrate to terminate and prevent recurrent arrhythmia. Arrhythmia targeting can be achieved with antiarrhythmic medications, catheter ablation, or more novel therapies, such as stereotactic radiation therapy, that target the arrhythmic substrate. Mechanistic studies point to adrenergic activation and other direct consequences of ICD shocks in promoting further arrhythmogenesis and hypocontractility. In this report, we review the pathophysiologic mechanisms, clinical features, prognosis, and therapeutic options for electrical storm. We also outline a clinical approach to this challenging and complex condition, along with its mechanistic basis.

Contemporary Management of Complex Ventricular Arrhythmias.

Percutaneous catheter ablation is an effective and safe therapy that can eliminate ventricular tachycardia, reducing the risks of both recurrent arrhythmia and shock therapies from a defibrillator. Successful ablation requires accurate identification of arrhythmic substrate and the effective delivery of energy to the targeted tissue. A thorough pre-procedural assessment is needed before considered 3D electroanatomical mapping can be performed. In contemporary practice, this must combine traditional electrophysiological techniques, such as activation and entrainment mapping, with more novel physiological mapping techniques for which there is an ever-increasing evidence base. Novel techniques to maximise energy delivery to the tissue must also be considered and balanced against their associated risks of complication. This review provides a comprehensive appraisal of contemporary practice and the evidence base that supports recent developments in mapping and ablation, while also considering potential future developments in the field.

Newer Methods for Ventricular Tachycardia Ablation and When to Use Them.

Radiofrequency (RF) catheter ablation has long been an important therapy for ventricular tachycardia and frequent symptomatic premature ventricular beats and nonsustained arrhythmias when antiarrhythmic drugs fail to suppress the arrhythmias. It is increasingly used in preference to antiarrhythmic drugs, sparing the patient adverse effects of drugs. Success of ablation varies with the underlying heart disease and type of arrhythmia: very effective for patients without structural heart disease, less effective in structural heart disease. Failure occurs when a target for ablation cannot be identified or ablation lesions fail to reach and abolish the arrhythmia substrate that may be extensive, intramural, or subepicardial in location. Approaches to improving ablation lesion creation are modifications to RF ablation and emerging investigational techniques. Easily- implemented modifications to RF methods include manipulating the size and location of the cutaneous dispersive electrode, increasing duration of RF delivery, and use of lower-tonicity catheter irrigation (usually 0.45% saline). When catheters can be placed on either side of culprit substrate, RF can be delivered in a bipolar or simultaneous unipolar configuration that can be successful. Catheters with extendable and retractable irrigated needles for delivery of RF are under investigation in clinical trials. Cryoablation is potentially useful with specific situations in which maintaining contact is difficult. Transvascular ethanol ablation and stereotactic radioablation have both shown promise for arrhythmias that fail other ablation strategies. Although substantial clinical progress has been achieved, further improvement is clearly needed. With ability to increase ablation lesion size, continued careful evaluation of safety, which has been excellent for standard RF ablation, remains important.

Imaging Modality Selection in Cardiac Ablation.

Catheter ablation as a treatment method for both ventricular and atrial arrhythmias has evolved significantly over the past 40 years since it was first performed in humans. This evolution has been paralleled by a similar expansion in both invasive and non-invasive imaging modalities directed at further elucidating cardiac morphology and arrhythmia substrate pathophysiology. Access to multimodality imaging options is a significant piece of the armamentarium available to interventional electrophysiologists who are tackling increasingly complex rhythm problems with catheter ablation. This presents a unique problem to the practicing electrophysiologist in selecting the most pertinent imaging modalities that will improve the safety and efficacy of a procedure and winnowing out potential imaging studies that offer minimal or marginal benefit. In this review, we evaluate the various modalities that are useful in planning and executing successful ablation and weigh the evidence for benefit.

Remote magnetic navigation for treatment of patients with atrial fibrillation

Atrial fibrillation (AF) remains an important medical and social health problem occupying a leading position among all cardiac arrhythmias in clinical practice. AF increases overall mortality by 1.9 times and the risk of stroke by 5 times, leads to disability among the working-age population, and reduces the quality of life. Pulmonary veins isolation is the main approach in the treatment of AF symptomatic patients who are resistant to antiarrhythmic therapy. However, the use of this technique is associated with the need for long-term use of fluoroscopy and monitoring of the contact force of the ablation catheter with the heart tissue for an effective and safe exposure on the arrhythmia substrate. In addition, the complication rate can reach up to 5% even when using non-fluoroscopic navigation systems. Over the past decade, robotic magnetic navigation was established as a safe and effective technology in the treatment of patients with different cardiac arrhythmias. The advantages of this technology are the flexibility and mobility of the ablation catheter to reach difficult areas during ablation procedure, as well as high efficiency and safety, with a low fluoroscopy exposure time. This review analyses the current literature and documents the experience of using robotic magnetic navigation for the treatment of patients with different forms of AF. We conducted searches on Scopus, Web of Science databases and PubMed. The reviewed studies demonstrated that the use of robotic magnetic navigation is a safe and highly effective method of treating patients with AF. It also helps to reduce the time of fluoroscopy during ablation procedure. Received 26 August 2021. Revised 21 September 2021. Accepted 22 September 2021. Funding: This work was carried out within the framework of the state task of Ministry of Health of Russian Federation No. 121031300225-8. Conflict of interest: The authors declare no conflict of interest. Contribution of the authorsConception and study design: V.V. Beloborodov, A.G. Filippenko, A.B. RomanovData collection and analysis: V.V. Beloborodov, N.А. Yelemessov, E.V. Fisher, A.G. Filippenko, V.V. Shabanov, A.B. RomanovStatistical analysis: A.B. Romanov, I.L. MikheenkoDrafting the article: V.V. Beloborodov, A.G. Filippenko, A.B. RomanovCritical revision of the article: A.B. Romanov, I.L. Mikheenko, A.G. Filippenko, V.V. ShabanovFinal approval of the version to be published: V.V. Beloborodov, V.V. Shabanov, N.А. Yelemessov, A.G. Filippenko, I.L. Mikheenko, E.V. Fisher, A.B. Romanov

Targeted cluster ablation of non-CTI-dependent atrial arrhythmias in congenital heart disease using ultrahigh-definition mapping.

Ablation of atrial arrhythmias in patients with congenital heart disease (CHD) has markedly improved with advanced mapping systems. However, recurrence rates remain high. The linear ablation strategy is not uncommonly practiced necessitating prolonged ablation times. We report the outcomes of adopting a strategy of minimal, cluster delivery of radiofrequency (RF) energy at critical substrates identified by ultrahigh-definition mapping for atrial arrhythmias in patients with CHD. Non-cavotricuspid isthmus (non-CTI) atrial tachycardias were ablated with a targeted ablation cluster technique (TACT) using an ultrahigh-density mapping system combined with multielectrode monitoring and endpoint determination in preference to linear ablation. The arrhythmia substrates, RF times, and acute- and medium-term success rates were studied. Fifty-eight tachycardias were mapped and ablated in 42 procedures: 34 non-CTIs and 24 CTIs. A targeted ablation cluster was performed for non-CTI tachycardias, with a median ablation time of 3.1 min. In 53% of non-CTI tachycardias, arrhythmia termination was achieved with ≤2 RF applications. After a mean follow-up of 23.6 months, 27 (80%) patients were free of recurrent atrial arrhythmias. One of 34 targeted non-CTI tachycardia recurred, with a final success rate of 91%. Linear ablation was performed for CTI flutters with a median ablation time of 6.8 min (vs. non-CTIs, p = .006). Three of 21 tachycardias recurred due to reconnection of the ablation line but the final success rate was 100%. The TACT approach for non-CTI atrial arrhythmias in congenital patients as guided by theultrahigh-density mapping is an effective method with short ablation times and excellent medium-term outcomes.

Zero-fluoroscopy ablation of left-sided arrhythmia substrates in children – Mid-term safety and feasibility study from transaortic approach

A widely used method of treating left-sided arrhythmia substrates in children is retrograde transaortic ablation under fluoroscopic guidance. However, the feasibility, safety, and efficacy of this approach under zero fluoroscopy (ZF) guidance, especially the mid-term safety of anatomy and function of aortic valves, have yet to be proven. All consecutive patients who received ablation of left-sided arrhythmias between January 2012 and June 2020 and below 20 years-old were enrolled. The study group submitted to 55ZF-guided procedures using cardiac mapping system (EnSite Precision), whereas 49 procedures were performed under fluoroscopic guidance in the control group. Echocardiographic studies took place before and 6-months after ablative procedures. One-hundred-and-two patients (male, 66; female, 36) underwent a total of 104 ablative procedures. Mean procedural durations were 83.9±44.4min in the study group and 64.8±29.1min in the control group, respectively (p=.01; the 95% confidence interval, -33.57 to -4.63). Corresponding fluoroscopic times were .5±2.2min and 24.7±13.9min (p<.001; the 95% confidence interval, 20.15 to 28.22). ZF may be reasonably applied after a learning curve of 20 cases. Immediate procedural success and recurrence rates were similar in each groups. There was no detectable progression of aortic regurgitation in any of the patients during serial follow-up of echocardiography. ZF-guided retrograde transaortic ablation of left-sided arrhythmia substrates proved safe in children at midterm follow-up, reducing radiation exposure significantly within a learning curve of <20 cases.

Detection of SARS-CoV-2 Antigens in the AV-Node of a Cardiac Conduction System—A Case Report

Mounting evidence indicates that new arrhythmic events frequently occur during and after coronavirus disease (COVID-19), posing additional mortality risk in older-aged and critically ill patients. However, the underlying mechanisms and cardio pathological substrates of COVID-related arrhythmias have not been clarified yet. Here, we report findings of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens and genes in the atrioventricular node (AV-node) of a cardiac conduction system, pointing to its direct infection as a possible arrhythmogenic factor.

Brugada Syndrome

Brugada syndrome (BrS) is an "inherited" condition characterized by predisposition to syncope and cardiac arrest, predominantly during sleep. The prevalence is ∼1:2,000, and is more commonly diagnosed in young to middle-aged males, although patient sex does not appear to impact prognosis. Despite the perception of BrS being an inherited arrhythmia syndrome, most cases are not associated with a single causative gene variant. Electrocardiogram (ECG) findings support variable extent of depolarization and repolarization changes, with coved ST-segment elevation ≥2 mm and a negative T-wave in the right precordial leads. These ECG changes are often intermittent, and may be provoked by fever or sodium channel blocker challenge. Growing evidence from cardiac imaging, epicardial ablation, and pathology studies suggests the presence of an epicardial arrhythmic substrate within the right ventricular outflow tract. Risk stratification aims to identify those who are at increased risk of sudden cardiac death, with well-established factors being the presence of spontaneous ECG changes and a history of cardiac arrest or cardiogenic syncope. Current management involves conservative measures in asymptomatic patients, including fever management and drug avoidance. Symptomatic patients typically undergo implantable cardioverter defibrillator insertion, with quinidine and epicardial ablation used for patients with recurrent arrhythmia. This review summarizes our current understanding of BrS and provides clinicians with a practical approach to diagnosis and management.

Beyond Ejection Fraction: Novel Clinical Approaches Towards Sudden Cardiac Death Risk Stratification in Patients with Dilated Cardiomyopathy.

Implantable Cardioverter-Defibrillator (ICD) therapy is indicated for patients at risk for sudden cardiac death due to ventricular tachyarrhythmia. The most commonly used risk stratification algorithms use Left Ventricular Ejection Fraction (LVEF) to determine which patients qualify for ICD therapy, even though LVEF is a better marker of total mortality than ventricular tachyarrhythmias mortality. This review evaluates imaging tools and novel biomarkers proposed for better risk stratifying arrhythmic substrate, thereby identifying optimal ICD therapy candidates.

Effects of azumolene on arrhythmia substrate in a model of recurrent long-duration ventricular fibrillation

BackgroundProarrhythmic risk of conventional anti-arrhythmic agents is linked to unintended modulation of membrane voltage dynamics. We have demonstrated that the anti-fibrillatory effect of azumolene is mediated via stabilization of the hyperphosphorylated ryanodine receptor (RyR2), leading to attenuation of diastolic calcium leak. However, the concomitant effects on membrane voltage dynamics have not been evaluated yet. MethodsAfter baseline optical mapping, Langendorff-perfused rabbit hearts treated with azumolene, or vehicle, were subjected to global ischemia-reperfusion (I/R) followed by two episodes of long-duration ventricular fibrillation (LDVF). Simultaneous dual epicardial calcium transient (CaT) and voltage dynamics were studied optically. ResultsPre-treatment with azumolene was associated with higher CaT amplitude alternans ratios (0.94 ± 0.02 vs. 0.78 ± 0.03 in control hearts, at 6 Hz; p = 0.005; and action potential amplitude alternans ratio (0.95 ± 0.02 vs. 0.78 ± 0.04 at 6.0 Hz; p = 0.02), and reduction of action potential duration (APD80) dispersion (9.0 ± 4.8 msec vs. 19.3 ± 6.6 msec at 6.0 Hz p = 0.02) and optical action potential upstroke rise time (26.3 ± 2.6 msec in control vs. 13.8 ± 0.6 msec at 6.0 Hz, p = 0.02) after LDVF. No change in action potential duration (APD) was noted with azumolene treatment. ConclusionIn a model of ischemic recurrent LDVF, treatment with azumolene led to reduction of cardiac alternans, i.e., calcium and voltage alternans. Unlike conventional anti-arrhythmic agents, reduction of action potential upstroke rise time and preservation of action potential duration following azumolene treatment may reduce the proarrhythmia risk.

High-resolution structure-function mapping of intact hearts reveals altered sympathetic control of infarct border zones.

Remodeling of injured sympathetic nerves on the heart after myocardial infarction (MI) contributes to adverse outcomes such as sudden arrhythmic death, yet the underlying structural mechanisms are poorly understood. We sought to examine microstructural changes on the heart after MI and to directly link these changes with electrical dysfunction. We developed a high-resolution pipeline for anatomically precise alignment of electrical maps with structural myofiber and nerve-fiber maps created by customized computer vision algorithms. Using this integrative approach in a mouse model, we identified distinct structure-function correlates to objectively delineate the infarct border zone, a known source of arrhythmias after MI. During tyramine-induced sympathetic nerve activation, we demonstrated regional patterns of altered electrical conduction aligned directly with altered neuroeffector junction distribution, pointing to potential neural substrates for cardiac arrhythmia. This study establishes a synergistic framework for examining structure-function relationships after MI with microscopic precision that has potential to advance understanding of arrhythmogenic mechanisms.

Mechanisms Underlying Antiarrhythmic Properties of Cardioprotective Agents Impacting Inflammation and Oxidative Stress.

The prevention of cardiac life-threatening ventricular fibrillation and stroke-provoking atrial fibrillation remains a serious global clinical issue, with ongoing need for novel approaches. Numerous experimental and clinical studies suggest that oxidative stress and inflammation are deleterious to cardiovascular health, and can increase heart susceptibility to arrhythmias. It is quite interesting, however, that various cardio-protective compounds with antiarrhythmic properties are potent anti-oxidative and anti-inflammatory agents. These most likely target the pro-arrhythmia primary mechanisms. This review and literature-based analysis presents a realistic view of antiarrhythmic efficacy and the molecular mechanisms of current pharmaceuticals in clinical use. These include the sodium-glucose cotransporter-2 inhibitors used in diabetes treatment, statins in dyslipidemia and naturally protective omega-3 fatty acids. This approach supports the hypothesis that prevention or attenuation of oxidative and inflammatory stress can abolish pro-arrhythmic factors and the development of an arrhythmia substrate. This could prove a powerful tool of reducing cardiac arrhythmia burden.

Artificially Created Reentry Circuit by Laser Irradiation Causes Atrial Tachycardia to Persist in Murine Atria.

There is a gradual progression from paroxysmal to persistent atrial fibrillation (AF) in humans. To elucidate the mechanism involved, the creation of an artificial atrial substrate to persist AF in mice was attempted.Methods and Results:This study used wild type (WT) mice, but it is difficult to induce AF in them. A novel antegrade perfusion method from the left ventricle (LV) to enlarge both atria for artificial atrial modification was proposed in this study. Short duration AF was induced by burst pacing under this method. Optical mapping analysis revealed non-sustained focal type and meandering spiral reentrants after short duration AF. A tiny artificial substrate (~1.2 mm in diameter) was added in by laser irradiation to create a critical atrial arrhythmogenic substrate. Burst pacing was performed in a non-laser group (n=8), a circular-shape laser group (n=8), and a wedge-shaped dent laser group (n=8). We defined AF and atrial tachycardia (AT) as atrial arrhythmia (AA). Long-lasting AA was defined as lasting for ≥30 min. Long-lasting AA was observed in 0/8, 0/8, and 6/8 (75%) mice in each group. Optical mapping analysis revealed that the mechanism was AT with a stationary rotor around the irradiated margin. Regrettably, this study failed to reproduce persistent AF, but succeeded in creating an arrhythmic substrate that causes sustained AT in WT mice.

Phenotypic Variability in iPSC-Induced Cardiomyocytes and Cardiac Fibroblasts Carrying Diverse LMNA Mutations.

Mutations in the LMNA gene (encoding lamin A/C) are a significant cause of familial arrhythmogenic cardiomyopathy. Although the penetrance is high, there is considerable phenotypic variability in disease onset, rate of progression, arrhythmias, and severity of myopathy. To begin to address whether this variability stems from specific LMNA mutation sites and types, we generated seven patient-specific induced pluripotent stem cell (iPSC) lines with various LMNA mutations. IPSC-derived cardiomyocytes (iCMs) and cardiac fibroblasts (iCFs) were differentiated from each line for phenotypic analyses. LMNA expression and extracellular signal-regulated kinase pathway activation were perturbed to differing degrees in both iCMs and iCFs from the different lines. Enhanced apoptosis was observed in iCMs but not in iCFs. Markedly diverse irregularities of nuclear membrane morphology were present in iCFs but not iCMs, while iCMs demonstrated variable sarcomere disarray. Heterogenous electrophysiological aberrations assayed by calcium indicator imaging and multi-electrode array suggest differing substrates for arrhythmia that were accompanied by variable ion channel gene expression in the iCMs. Coculture studies suggest enhancement of the LMNA mutation effects on electrophysiological function exerted by iCFs. This study supports the utility of patient-specific iPSC experimental platform in the exploration of mechanistic and phenotypic heterogeneity of different mutations within a cardiac disease-associated gene. The addition of genetically defined coculture of cardiac-constituent non-myocytes further expands the capabilities of this approach.

The Outcome of Ventricular Arrhythmias Associated With Mitral Valve Prolapse After Catheter Ablation: A Systematic Review and Meta-Analysis.

The presence of mitral valve prolapse (MVP) varies from asymptomatic to life-threatening arrhythmias. Catheter ablation (CA) is widely used to treat ventricular arrhythmias (VAs) associated with MVP. Despite having high procedural success, outcome data after CA is limited, especially in a long-term setting. Therefore, this systematic review and meta-analysis were performed. Literature searching was conducted in Pubmed, EuropePMC, Proquest, and Ebsco from inception to December 2020 using keywords: ventricular arrhythmia, premature ventricular complex, ventricular tachycardia, ventricular fibrillation, mitral valve prolapse, and catheter ablation. A total of 407 potential articles were retrieved for further review. The final review resulted in six articles for systematic review and meta-analysis. The study was registered in PROSPERO (CRD42020219144). The most common origin of VAs was papillary muscle. The acute success rate of CA in the MVP group varies between 66% and 94%. Follow-up studies reported a higher percentage of VAs recurrence after CA in the MVP group (22.22%) compared with the non-MVP group (11.38%). However, the difference is not significant (P-value = 0.16). Other studies reported a 12.5%-36% rate and 40% of repeat ablation in the medium term and the long term, respectively. Episodes of sudden cardiac death during exertion could still occur following CA in patients with MVP. Distinct origin of VAs was observed during repeated ablation procedures, which may explain arrhythmic substrate progression. Diffuse left ventricular fibrosis around papillary muscle rather than local fibrosis was observed among older patients. Furthermore, the presence of mitral annular disjunction (MAD) and Filamin C mutation might increase the risk of recurrent VAs. CAn has been done as the treatment of VAs associated with MVP. The acute success rate of CA varies between studies and the number of patients requiring repeat CA varied from 12.5% to 40%. Sudden cardiac death could still occur after CA. Older age during CA, genetic predisposition, deep arrhythmic foci, multifocal VAs origin, diffuse fibrosis, and the presence of MAD may contribute to the recurrence of VAs. Further studies, stratification, and evaluation are needed to prevent fatal outcomes in VA associated with MVP, even after CA.

Toward radiofrequency catheter ablation of atrial fibrillation.

Curative treatments of supraventricular arrhythmias—that is, aiming at the elimination of arrhythmic substrate—were initially performed in the 1970s during cardiac surgery as a last resort. A tandem team of surgeons and electrophysiologists intervened, as the individual location of substrate required mapping guidance of the electrical anomaly. In the early 1980s, catheter ablation began using direct current (DC) shocks, with most procedures being palliative as they aimed at interrupting atrioventricular (AV) conduction in patients with uncontrolled ventricular rate associated with atrial fibrillation (AF) or AV nodal reentrant tachycardia (AVNRT).