Sustained bundle branch reentry as a mechanism of clinical tachycardia

Mid-term outcome of catheter ablation of idiopathic non-outflow tract ventricular arrhythmias

BACKGROUND

Catheter ablation is recommended in patients with frequent and symptomatic ventricular arrhythmias (VAs) in an otherwise normal heart. Right or left outflow tract (OT) are the most common origins, and catheter ablation is highly effective with low complication rates. However, outcome of catheter ablation of VAs other than the OT (non-OTVAs) is limited. The aim of this single-center study was to assess the safety and mid-term outcome of catheter ablation for non-OTVAs.

METHOD AND RESULTS

From 2013 to 2018, 251 patients who underwent catheter ablation for idiopathic non-OTVAs were enrolled and grouped according to the origins including His-Purkinje system (HPS, n = 108), papillary muscle / moderator band (PM/MB, n = 47), tricuspid annulus (TA, n = 70), and mitral annulus (MA, n = 26), 244 (97.2%) had acute elimination of VAs. The time of VAs recurrence of the single procedure was 1.69 (0.12,9.72) months, with 66% occurring within the first 3 months. The recurrence rate was significantly higher in the PM/MB group than in the TA (p = 0.025) and MA groups (p = 0.023). The single procedure success rate in all patients was 70.1%, in which 66.7%, 59.6%, 80%, and 76.9% were achieved in the HPS, PM/MB, TA, and MA groups, respectively (p = 0.284). After multiple procedures, the total success rate was 76.5% at the follow-up of 4.38 ± 2.42 years. The rate was significantly lower in the PM/MB group than in the TA group (p = 0.035). In subgroup analysis, no significant difference was observed in the recurrence rate of single procedure in patients with different VA origins within the PM/MB (log-rank test, p = 0.546).

CONCLUSION

Despite a certain percentage of recurrences observed in the mid-term follow-up, catheter ablation remained feasible and effective for idiopathic non-OTVAs.

Fascicular Ventricular Tachycardias: Potential Role of the Septal Fascicle

Ventricular tachycardias involving the fascicular system are amongst the most challenging and intriguing arrhythmias for cardiac electrophysiologists. Although some of the more common forms have been recognized clinically for decades, other variants continue to be characterized. Moreover, considerable uncertainty persists to date with regards to the mechanisms underpinning these arrhythmias. In this state-of-the-art review, we discuss the seminal historical and contemporary observations that have collectively advanced our understanding of fascicular ventricular tachycardias. From this base, we canvas the basic and clinical evidence supporting a potential role for the septal fascicular network and propose a new schema hypothesizing involvement of this fascicle. Although we focus primarily on the most common left posterior fascicular ventricular tachycardia, our discussion and proposal have mechanistic and therapeutic implications for the spectrum of fascicular arrhythmias.

Progressive outcomes of bundle branch reentrant ventricular tachycardia in patients without structural heart disease

BACKGROUND

Ablation strategies to treat bundle branch reentrant ventricular tachycardia (BBRT) are well described. However, reports of long-term follow-up outcomes in BBRT patients without structural heart disease (SHD) are limited.

OBJECTIVE

The purpose of this study was to investigate the long-term follow-up prognosis of BBRT patients without SHD.

METHODS

Changes in electrocardiographic and echocardiographic parameters were used to evaluate progression during follow-up. Potential pathogenic candidate variants were screened using a specific gene panel.

RESULTS

Eleven consecutive BBRT patients without obvious SHD based on echocardiographic and cardiovascular magnetic resonance imaging results were enrolled. Median age was 20 (11-48) years, and median follow-up time was 72 months. During follow-up, PR interval [206 (158-360) ms vs 188 (158-300) ms; P = .018] and QRS duration [187 (155-240) ms vs 164 (130-178) ms; P = .008] each increased significantly compared with postablation. Right- and left-sided chamber dilation and reduced left ventricular ejection fraction (LVEF) also were observed. Clinical deterioration or events occurred in 8 patients: 1 sudden death; 3 both complete heart block and reduced LVEF; 2 significantly reduced LVEF; and 2 prolonged PR interval. Genetic testing results showed that 6 of 10 patients (excluding the patient with sudden death) had ≥1 potential pathogenic candidate variants.

CONCLUSION

Further deterioration of His-Purkinje system conduction was observed in young BBRT patients without SHD after ablation. The His-Purkinje system may be the first target of genetic predisposition.

Catheter Ablation for Ventricular Tachycardia Involving the His-Purkinje System: Fascicular and Bundle Branch Reentrant Ventricular Tachycardia

The Purkinje system has been found to mediate several monomorphic ventricular tachycardias (VTs). These include fascicular VTs and bundle branch reentrant (BBR) VTs. Previous studies have revealed that VTs involving the His-Purkinje system are composed of multiple discrete subtypes that are best differentiated by their mechanism, drug effect, VT morphology, and successful ablation site. Recognition of the heterogeneity of these VTs and their unique characteristics should facilitate the appropriate diagnosis and therapy and help guide catheter ablation therapy. In this article, we focus on the latest updates of the mechanisms underlying left ventricle fascicular VTs and BBR-VTs as well as the latest catheter ablation techniques.

R-on-T and the initiation of reentry revisited: Integrating old and new concepts

Initiation of reentry requires 2 factors: (1) a triggering event, most commonly focal excitations such as premature ventricular complexes (PVCs); and (2) a vulnerable substrate with regional dispersion of refractoriness and/or excitability, such as occurs during the T wave of the electrocardiogram when some areas of the ventricle have repolarized and recovered excitability but others have not. When the R wave of a PVC coincides in time with the T wave of the previous beat, this timing can lead to unidirectional block and initiation of reentry, known as the R-on-T phenomenon. Classically, the PVC triggering reentry has been viewed as arising focally from 1 region and propagating into another region whose recovery is delayed, resulting in unidirectional conduction block and reentry initiation. However, more recent evidence indicates that PVCs also can arise from the T wave itself. In the latter case, the PVC initiating reentry is not a separate event from the T wave but rather is causally generated from the repolarization gradient that manifests as the T wave. We call the former an "R-to-T" mechanism and the latter an "R-from-T" mechanism, which are initiation mechanisms distinct from each other. Both are important components of the R-on-T phenomenon and need to be taken into account when designing antiarrhythmic strategies. Strategies targeting suppression of triggers alone or vulnerable substrate alone may be appropriate in some instances but not in others. Preventing R-from-T arrhythmias requires suppressing the underlying dynamic tissue instabilities responsible for producing both triggers and substrate vulnerability simultaneously. The same principles are likely to apply to supraventricular arrhythmias.

Simultaneous narrow and wide QRS complex tachycardia: Misdiagnosis or Missed diagnosis?

Tachycardia-induced tachycardia, or so-called double tachycardia, appears to be a relatively rare condition. Regardless of the mechanism, this case illustrates the importance of assessing the response to multiple different pacing maneuvers in determining the mechanism of narrow and wide QRS complex tachycardias, rather than relying upon a single maneuver, even one that is believed to be diagnostic. This article is protected by copyright. All rights reserved.

Management of ventricular arrhythmias in heart failure: Current perspectives

Congestive heart failure (HF) is a progressive affliction defined as the inability of the heart to sufficiently maintain blood flow. Ventricular arrhythmias (VAs) are common in patients with HF, and conversely, advanced HF promotes the risk of VAs. Management of VA in HF requires a systematic, multimodality approach that comprises optimization of medical therapy and use of implantable cardioverter-defibrillator and/or device combined with cardiac resynchronization therapy. Catheter ablation is one of the most important strategies with the potential to abolish or decrease the number of recurrences of VA in this population. It can be a curative strategy in arrhythmia-induced cardiomyopathy and may even save lives in cases of an electrical storm. Additionally, modulation of the autonomic nervous system and stereotactic radiotherapy have been introduced as novel methods to control refractory VAs. In patients with end-stage HF and refractory VAs, an institution of the mechanical circulatory support device and cardiac transplant may be considered. This review aims to provide an overview of current evidence regarding management strategies of VAs in HF with an emphasis on interventional treatment.

Bundle Branch Re-Entrant Ventricular Tachycardia after Minimal Invasive Cardiac Surgery

Background: Bundle branch re-entrant ventricular tachycardia (BBRVT) is a monomorphic ventricular arrhythmia with wide QRS complexes caused by re-entrant tachycardia between both bundle branches. BBRVT can occur in a variety of cardiac pathologies with His–Purkinje system (HPS) conduction abnormalities such as dilated cardiomyopathy, coronary artery disease, hypertrophic cardiomyopathy, valvular heart disease and even after aortic valve surgery. Case report: A 62-year-old male patient with an ischemic cardiomyopathy and implantable cardioverter defibrillator (ICD) underwent minimal invasive aortic valve replacement (Yil-AVR) and coronary artery bypass graft (CABG). He was remitted a week later because of relapsing sustained ventricular tachycardia (VT). Electrocardiogram showed a wide QRS tachycardia, which was remarkably similar to the patient’s sinus rhythm. Analysis of ICD revealed the presence of BBRVT. Catheter ablation of the right bundle branch (RBB) was performed. He is currently in clinical follow-up and no reoccurrence of VT has been recorded so far. Conclusion: Patients with known cardiomyopathy can develop BBRVT early after cardiac surgery. To our knowledge, this is the first time that BBRVT occurred after Yil-AVR.

Diagnosis and Management of Complex Reentrant Arrhythmias Involving the His-Purkinje System

The His-Purkinje system is a network of bundles and fibres comprised of specialised cells that allow for coordinated, synchronous activation of the ventricles. Although the histology and physiology of the His-Purkinje system have been studied for more than a century, its role in ventricular arrhythmias has recently been discovered with the ongoing elucidation of the mechanisms leading to both benign and life-threatening arrhythmias. Studies of Purkinje-cell electrophysiology show multiple mechanisms responsible for ventricular arrhythmias, including enhanced automaticity, triggered activity and reentry. The variation in functional properties of Purkinje cells in different areas of the His-Purkinje system underlie the propensity for reentry within Purkinje fibres in structurally normal and abnormal hearts. Catheter ablation is an effective therapy in nearly all forms of reentrant arrhythmias involving Purkinje tissue. However, identifying those at risk of developing fascicular arrhythmias is not yet possible. Future research is needed to understand the precise molecular and functional changes resulting in these arrhythmias.

Flecainide in Ventricular Arrhythmias: From Old Myths to New Perspectives

Flecainide is an IC antiarrhythmic drug (AAD) that received in 1984 Food and Drug Administration approval for the treatment of sustained ventricular tachycardia (VT) and subsequently for rhythm control of atrial fibrillation (AF). Currently, flecainide is mainly employed for sinus rhythm maintenance in AF and the treatment of idiopathic ventricular arrhythmias (IVA) in absence of ischaemic and structural heart disease on the basis of CAST data. Recent studies enrolling patients with different structural heart diseases demonstrated good effectiveness and safety profile of flecainide. The purpose of this review is to assess current evidence for appropriate and safe use of flecainide, 30 years after CAST data, in the light of new diagnostic and therapeutic tools in the field of ischaemic and non-ischaemic heart disease.

Bundle Branch Reentrant Ventricular Tachycardia Treated with Catheter Ablation in a Patient with Myotonic Dystrophy

BACKGROUND Bundle branch reentrant ventricular tachycardia (BBRVT) is a rarely encountered ventricular tachycardia (VT) and is classically associated with advanced heart diseases. Importantly, the tachycardia is readily curable with catheter ablation. Without suspicion of BBRVT and recording of the His-Purkinje system, it is hard to diagnose accurately. Myotonic dystrophy (MD) is the most common neuromuscular disease in adults and is known to have a risk of development of BBRVT. Here, we report a case of BBRVT in an MD patient with normal cardiac configuration with typical clinical and electrophysiological features. CASE REPORT A 40-year-old man presented with chest discomfort and weakness at the Emergency Department with unstable vital conditions. Electrocardiography showed wide QRS tachycardia with right bundle branch block pattern. The patient had been diagnosed with MD (type I) 3 years ago and had typical clinical features of MD. Transthoracic echocardiography showed normal left ventricular systolic function and no significant structural abnormalities. In the electrophysiologic study, VTs with left and right bundle branch block pattern were induced and diagnosed with BBRVT. Considering the risk of sudden death, implantation of an implantable cardioverter-defibrillator (ICD) was performed. One month later, VT had recurred and was successfully treated with ablation of the right bundle branch. CONCLUSIONS We present a case of 2 different morphologies of BBRVT in a patient with MD and normal ventricular function. Catheter ablation is a curative method for BBRVT and can be a tool for reducing ICD shock.

Alternating wide complex tachycardia after surgical aortic valve replacement

A 51-year-old male developed recurrent episodes of palpitations and pre-syncope after surgical aortic valve replacement. Electrocardiograms after surgery revealed a wide complex tachycardia with alternating left bundle branch and right bundle branch block morphologies. An electrophysiology study (EPS) demonstrated typical bundle branch reentry ventricular tachycardia (BBRVT) treated successfully with right bundle ablation. We demonstrate the key diagnostic features of BBRVT on EPS, describe the circuit of BBRVT with explanation of the HV pseudointerval, and highlight the association of BBRVT and valve replacement.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Syncope After Transcatheter Aortic Valve Replacement: Two Faces of Abnormal Intraventricular Conduction

Conduction system damage is the most common complication of transcatheter aortic valve replacement (TAVR), which frequently requires placement of a permanent pacemaker. Bundle branch reentry (BBR) is a well-recognized mechanism of ventricular tachycardia (VT) in the setting of abnormal intraventricular conduction. We describe a case of a patient with post-TAVR intraventricular conduction abnormalities who presented with intermittent advanced atrioventricular block and BBR VT and discuss the potential risks, diagnosis, and management of BBR after TAVR.

Sustained Monomorphic Ventricular Tachycardia in Nonischemic Heart Disease

As the population of patients with implanted defibrillators has grown, an increasing number of patients nonischemic cardiomyopathies are requiring therapy to reduce ventricular arrhythmias. Most of these arrhythmias are related to areas of ventricular scar. Although the pathophysiology of scar development is not well understood in these diseases, advances in cardiac imaging and mapping are better characterizing the scar locations that give rise to the arrhythmias. Here, we review the pathophysiologic and electrocardiographic correlations that inform ablation strategies for ventricular tachycardia in these diseases.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Bundle branch reentrant ventricular tachycardia: review and case presentation

Bundle branch reentrant ventricular tachycardia (BBRVT) is characterized by a unique, fast (200-300 beats/min), monomorphic wide complex tachycardia (WCT) associated with syncope, hemodynamic compromise, and cardiac arrest. It is challenging to diagnose, requiring a His bundle recording and specific pacing maneuvers. The overall incidence has been reported to be up to 20% among patients with non-ischemic cardiomyopathy (NICM) undergoing electrophysiologic studies. We report a case of BBRVT in a patient with ischemic cardiomyopathy (ICM) presenting as a WCT with recurrent implantable-cardioverter-defibrillator (ICD) shocks. We describe all the characteristic features of BBRVT and discuss its differential. We also discuss the role of ablation for this condition.

Ventricular arrhythmias involving the His-Purkinje system in the structurally abnormal heart

His-Purkinje-related ventricular arrhythmias are a subset of ventricular tachycardias that use the specialized cardiac conduction system. These arrhythmias can occur in various different forms of structural heart disease. Here, we review the basic science discoveries and their analogous clinical observations that implicate the His-Purkinje system as a crucial component of the arrhythmia circuit. While mutations serve the molecular basis for arrhythmias in the heritable cardiomyopathies, transcriptional and posttranslational changes constitute the adverse remodeling leading to arrhythmias in acquired structural heart disease. Additional studies on the electrical properties of the His-Purkinje network and its interactions with the surrounding myocardium will improve the clinical diagnosis and treatment of these arrhythmias.

Peculiar Electrocardiographic Aspects of Wide QRS Complex Tachycardia: When Differential Diagnosis Is Difficult

Wide complex tachycardia may represent a challenge for correct interpretation of standard electrocardiogram, which is crucial for proper patient management. For this reason, algorithms based on electrocardiographic criteria have been developed to guide interpretation in a step-by-step approach. Despite their greater accuracy, some cases of wide QRS complex tachycardia are a challenge. Some peculiar forms of ventricular tachycardia, and complex supraventricular substrate or particular clinical condition, may originate a challenging electrocardiographic pattern. In this article, a series of peculiar cases of wide QRS complex tachycardia is presented as paradigm of how important a comprehensive clinical approach is in these patients.

Cellular Physiology and Clinical Manifestations of Fascicular Arrhythmias in Normal Hearts

Fascicular ventricular arrhythmias represent a spectrum of ventricular tachycardias dependent on the specialized conduction system. Although they are more common in structurally abnormal hearts, there is an increasing body of literature describing their role in normal hearts. In this review, the authors present data from both basic and clinical research that explore the current understanding of idiopathic fascicular ventricular arrhythmias. Evaluation of the cellular electrophysiology of the Purkinje cells shows clear evidence of enhanced automaticity and triggered activity as potential mechanisms of arrhythmias. Perhaps more importantly, heterogeneity in conduction system velocity and refractoriness of the left ventricular conduction system in animal models are in line with clinical descriptions of re-entrant fascicular arrhythmias in humans. Further advances in our understanding of the conduction system will help bridge the current gap between basic science and clinical fascicular arrhythmias.

Is It Complete Left Bundle Branch Block? Just Ablate the Right Bundle

Complete left bundle branch block (LBBB) is established according to standard electrocardiographic criteria. However, functional LBBB may be rate-dependent or can perpetuate during tachycardia due to repetitive concealed retrograde penetration of impulses through the contralateral bundle "linking phenomenon." In this brief article, we present two patients with basal complete LBBB in whom ablating the right bundle unmasked the actual antegrade conduction capabilities of the left bundle. These cases highlight intriguing overlap between electrophysiological concepts of complete block, linking, extremely slow, and concealed conduction.

Mechanisms of sudden cardiac death

Sudden cardiac death (SCD) continues to be a major public health problem and is thought to account for almost half of all cardiac deaths. Cardiac arrest and SCD are most commonly due to ventricular arrhythmias. Most patients who suffer cardiac arrest have underlying structural heart disease, with coronary artery disease (CAD) being the most common. In the setting of CAD, ventricular arrhythmias can result due to acute ischemia in the absence of preexisting myocardial scarring or in the presence of established scar from prior infarction without clinically significant ischemia. LV systolic dysfunction is an important predictor of risk for SCD in ischemic heart disease and in most nonischemic disorders, although other factors such as ventricular hypertrophy also play a role. Cardiac arrest and SCD can also occur due to primary electrical disorders in the absence of major structural abnormalities.

Human His-Purkinje System: Abnormalities of Conduction, Rhythm Disorders and Case Studies

This review covers many of the arrhythmias and conduction abnormalities related to His-Purkinje System. These include junctional premature complexes, junctional and fascicular tachycardias, bundle branch reentry (BBR), and the role of apparent conduction in various forms of supraventricular tachycardias (SVT) with or without involvement of accessory pathways (AP).

Bundle branch reentry: A rare mechanism of ventricular tachycardia in endomyocardial fibrosis, without ventricular dilation

Introduction

Bundle branch reentry as a mechanism of ventricular tachycardia (VT) in endomyocardial fibrosis (EMF) is not described.

Case report

A 52-year-old woman with left ventricular (LV) EMF had VT needing cardioversion. She had mitral regurgitation and left bundle branch block, but no LV dilation or heart failure. During electrophysiological study, clinical VT could be easily induced, and it was confirmed to be bundle branch reentrant VT (BBRVT). She was treated with ablation of the right bundle branch.

Conclusion

BBRVT can occur in EMF even without cardiac dilatation. Its recognition is important, as radiofrequency ablation can be curative.

Spectrum of Fascicular Arrhythmias

Fascicular arrhythmias encompass a wide spectrum of ventricular arrhythmias that depend on the specialized conduction system of the right and left ventricles. These arrhythmias include premature ventricular complexes, monomorphic ventricular tachycardia, polymorphic ventricular tachycardia, and ventricular fibrillation. These arrhythmias may be organized by mechanism, including intrafascicular reentry, interfascicular reentry, and focal. Mapping and ablation of the fascicular system can result in high cure rates of debilitating and potentially life-threatening arrhythmias. When approaching these arrhythmias, careful consideration of the structure of the His Purkinje system as well as their electrophysiologic properties may help guide even the most complex of arrhythmias.

Prevention of sudden cardiac death beyond the ICD: have we reached the boundary or are we just burning the surface?

Preventing sudden cardiac death (SCD) remains a major unsolved problem in contemporary medical practice. As the most common cause of SCD, treatment for ventricular arrhythmias is the target area of interest in research field. While implantable cardioverter-defibrillator (ICD) effectively decreases death from ventricular arrhythmias in highly selected patients, risk of inappropriate shocks, mortality from frequent therapy, chance of failing in abortion of arrhythmias despite having a defibrillator, and our inability to recognize which of several hundreds of thousands of patients at risk for sudden death but do not meet current criteria for defibrillator, limit ICD effectiveness. In this article, a brief review of mechanism leading to SCD, the existing evidence for a defibrillator and the lacunae in present guidelines for patients clearly at risk for sudden death but without proven benefit from a defibrillator are presented in Section I. Following this, interventional approaches, both catheter-based and general measures that may serve as adjuncts to a defibrillator in preventing this all too common catastrophic end event, are summarized in Section II.