Bilateral Cardiac Sympathectomy and Extrapericardial Coil Implantation for the Management of Electrical Storm.

We present a novel multidisciplinary approach for the treatment of electrical storm combining bilateral cardiac sympathectomy, extrapericardial coil insertion, and implantable cardioverter defibrillator upgrade in a patient with nonischemic cardiomyopathy and ventricular arrhythmias refractory to conventional therapies. (Level of Difficulty: Advanced.).

The Rapidly-Developing Area of Radiocardiology: Principles, Complications and Applications of Radiotherapy on the Heart.

Ventricular arrhythmias are the leading cause of sudden cardiac death. Current treatment strategies for ventricular tachycardia, including antiarrhythmic drugs and catheter ablation, have limited efficacy in patients with structural heart disease. Noninvasive ablation with the use of externally applied radiation (cardiac radioablation) has emerged as a promising and novel approach to treating recurrent ventricular tachycardias. However, the heart is generally an "organ at risk" for radiation treatments, such that very little is known on the effects of radiotherapy on cardiac ultrastructure and electrophysiologic properties. Furthermore, there has been limited interaction between the fields of cardiology and radiation oncology and physics. The advent of cardiac radioablation will undoubtedly increase interactions between cardiologists, cardiac electrophysiologists, radiation oncologists and physicists. There is an important knowledge gap separating these specialties, but scientific developments, technical optimisation, and improvements depend on intense multidisciplinary collaboration. This manuscript seeks to review the basic of radiation physics and biology for cardiovascular specialists in an effort to facilitate constructive scientific and clinical collaborations to improve patient outcomes.

Fusion pacing in patients with right bundle branch block who undergo cardiac resynchronization therapy.

PURPOSE: Patients with right bundle branch block (RBBB) are less likely to respond to cardiac resynchronization therapy (CRT). We aimed to assess whether patients with RBBB respond to CRT with biventricular fusion pacing. METHODS: Consecutive patients with RBBB at a single tertiary care center, who were implanted with a CRT device capable of biventricular fusion pacing using SyncAV programming, were assessed and compared to a historical cohort of CRT patients with RBBB. QRSd was measured and compared during intrinsic conduction, nominal CRT pacing and manual electrocardiogram-based optimized SyncAV programming. Left ventricular ejection fraction (LVEF) was also compared before and 6 months after CRT. RESULTS: We included 8 consecutive patients with RBBB (group 1) who were able to undergo SyncAV programming and 16 patients with RBBB (group 2) from a historical cohort. In group 1, compared to mean intrinsic conduction QRSd (155 ± 13 ms), mean nominally-paced QRSd was 156 ± 15 ms (ΔQRSd 1.3 ± 11.6; p = 0.77) and SyncAV-optimized paced QRSd was 135 ± 14 ms (ΔQRSd -20.0 ± 20.4; p = 0.03 and ΔQRSd -21.3 ± 16.3; p = 0.008; compared to intrinsic conduction and nominal pacing respectively). In group 2, mean QRSd with nominal pacing was 160 ± 24 ms (ΔQRSd 3.8 ± 33.4; p = 0.66 compared to intrinsic conduction). In group 1, baseline LVEF was 22.1 ± 11.5 and after 6 months of follow-up was 27.8 ± 8.6 (p = 0.047). In group 2, the baseline LVEF was 27.2 ± 10.6 and after 6 months of follow-up was 25.0 ± 10.0 (p = 0.45). CONCLUSIONS: CRT programed to allow biventricular fusion pacing significantly improved electrical synchrony and LVEF in patients with RBBB. Larger studies are required to confirm these findings.

Catheter Ablation of Atrial Fibrillation: Current and Evolving Indications.

Catheter ablation (CA) was developed as a potentially curative procedure through electrical isolation of the pulmonary veins to isolate the main triggers of atrial fibrillation (AF). When successful, CA has clearly been shown to decrease AF recurrence and symptoms, and improve quality of life. With advancing technology, increased procedural success, and lower complication risk, CA is being used at much higher rates, with broader indications and in a diverse AF population. Symptomatic paroxysmal AF that is refractory to antiarrhythmic drugs is currently the indication for CA with the best evidence. CA for AF as first-line therapy is reserved for highly selected symptomatic patients with paroxysmal AF. Current studies have not shown an improvement in mortality or quality of life with CA as first-line therapy. In patients with persistent AF who are symptomatic despite medical therapy, CA is a reasonable therapeutic option. Although recent trials have suggested that CA reduced mortality and hospitalizations in patients with heart failure and reduced ejection fraction, the evidence is not conclusive. Therefore, current guidelines recommend CA for similar indications to patients without heart failure, but large trials comparing CA with strict rate control will be reported in the near future. Ongoing studies will assess whether CA of AF reduces major adverse cardiovascular events and whether stopping anticoagulation in the long term is possible after CA. The purpose of this review is to outline the current and evolving indications for CA of AF and the underlying evidence supporting these indications.

Optimization of Chronic Cardiac Resynchronization Therapy Using Fusion Pacing Algorithm Improves Echocardiographic Response.

BACKGROUND: Whether reprogramming of cardiac resynchronization therapy (CRT) to increase electrical synchrony translates into echocardiographic improvement remains unclear. SyncAV is an algorithm that allows fusion of intrinsic conduction with biventricular pacing. We aimed to assess whether reprogramming chronically implanted CRT devices with SyncAV is associated with improved echocardiographic parameters. METHODS: Patients at a quaternary center with previously implanted CRT devices with a programmable SyncAV algorithm underwent routine electrocardiography-based SyncAV optimization during regular device clinic visits. This analysis included only patients who could be programmed to the SyncAV algorithm (i.e., in sinus rhythm with intrinsic atrioventricular conduction). Echocardiography was performed before and 6 months after CRT optimization. RESULTS: Of 64 consecutive, potentially eligible patients who underwent assessment, 34 who were able to undergo SyncAV programming were included. Their mean age was 74 ± 9 years, 41% were female, and 59% had ischemic cardiomyopathy. The mean time from CRT implant to SyncAV optimization was 17.8 ± 8.5 months. At 6-month follow-up, SyncAV optimization was associated with a significant increase in left ventricular ejection fraction (LVEF) (mean LVEF 36.5% ± 13.3% vs 30.9% ± 13.3%; P < 0.001) and a reduction in left ventricular end-systolic volume (LVESV) (mean LVESV 110.5 ± 57.5 mL vs 89.6 ± 52.4 mL; P < 0.001) compared with baseline existing CRT programming. CONCLUSION: CRT reprogramming to maximize biventricular fusion pacing significantly increased LVEF and reduced LVESV in patients with chronic CRT devices. Further studies are needed to assess if a continuous fusion pacing algorithm improves long-term clinical outcomes and to identify which patients are most likely to derive benefit.

CONTEXTE: On ignore si la reprogrammation du dispositif de resynchronisation cardiaque (DRC) afin d'améliorer la synchronisation électrique se traduit réellement par une amélioration échocardiographique. L'algorithme SyncAV permet de fusionner la conduction intrinsèque et la stimulation biventriculaire. Nous avons tenté de déterminer si la reprogrammation à l'aide de l'algorithme SyncAV d'un DRC implanté de façon permanente permet d'améliorer les paramètres échocardiographiques. MÉTHODOLOGIE: Les patients d'un centre de soins quaternaires porteurs d'un DRC doté d'un algorithme SyncAV programmable ont subi une optimisation électrocardiographique de routine de cet algorithme à l'occasion d'une consultation de suivi. L'analyse ne portait que sur les patients dont le dispositif pouvait être programmé au moyen de l'algorithme SyncAV (c.-à-d. en rythme sinusal avec conduction auriculoventriculaire intrinsèque). Une échocardiographie a été réalisée avant l'optimisation du DRC, puis 6 mois après. RÉSULTATS: Sur les 64 patients consécutifs potentiellement admissibles qui ont fait l'objet d'une évaluation, 34 sujets dont le DRC pouvait être programmé à l'aide de l'algorithme SyncAV ont été retenus. Les sujets avaient en moyenne 74 ± 9 ans; 41 % d'entre eux étaient des femmes, et 59 % présentaient une cardiomyopathie ischémique. Le temps écoulé entre l'implantation du DRC et l'optimisation au moyen de l'algorithme SyncAV était en moyenne de 17,8 ± 8,5 mois. Au moment du suivi à 6 mois, l'optimisation au moyen de l'algorithme SyncAV a été associée à une augmentation significative de la fraction d'éjection ventriculaire gauche (FEVG) (FEVG moyenne de 36,5 % ± 13,3 % vs 30,9 % ± 13,3 %; p < 0,001) et à une réduction du volume télésystolique ventriculaire gauche (VTSVG) (VTSVG moyen de 110,5 ± 57,5 mL vs 89,6 ± 52,4 mL; p < 0,001) comparativement à la programmation initiale du DRC. CONCLUSION: La reprogrammation du DRC afin de maximiser la stimulation biventriculaire par fusion a considérablement augmenté la FEVG et réduit le VTSVG chez les patients porteurs d'un DRC permanent. D'autres études sont nécessaires pour déterminer si un algorithme de stimulation par fusion en continu permet d'améliorer les résultats cliniques à long terme et pour établir le profil des patients les plus susceptibles de bénéficier d'une telle intervention.

The use of adenosine to identify dormant conduction after accessory pathway ablation: a single center experience and literature review.

INTRODUCTION: Atrio-ventricular reentrant tachycardias (AVRT) represent around 40 percent of supraventricular tachycardias. After ablation, recurrence rates are around 10 percent. Adenosine has been described as a useful tool to assess presence of dormant conduction and predict recurrence after apparently successful ablation. We reviewed the patients of our service and assessed the role of adenosine in predicting dormant conduction and factors that could influence recurrence rates. METHODS: We retrospectively reviewed electrophysiologic studies and medical charts of 65 patients who had AVRT ablation and had adenosine used to assess dormant conduction at a single quaternary center between 2011 and 2015. Dormant conduction was defined as transient recovery of the preexcitation (for pathways with antegrade conduction) or return of the retrograde conduction through an apparently successfully ablated concealed accessory pathway (AP). RESULTS: One patient was found to have dormant conduction (1.5%) with early recurrence that was not further ablated due to the difficult location of the AP. The overall recurrence rate was 4.6%. General features like location of AP's, their properties, ablation times and technique were assessed. CONCLUSION: Similar to its use in identifying other arrhythmias, adenosine may be useful in identifying dormant conduction for further ablation during initial ablation of an accessory pathway; however, the absence of dormant conduction on adenosine testing does not reliably predict non-recurrence. The low recurrence rates in our service may be related to the frequent use of irrigated tip catheters, 3D mapping and long average ablation time over the successful site of ablation.

Incidence and Predictors of Intracardiac Thrombus on Pre-electrophysiological Procedure Transesophageal Echocardiography.

BACKGROUND: Cerebral thromboembolism is a potentially devastating complication of atrial fibrillation (AF) and atrial flutter (AFl). The use of transesophageal echocardiogram (TEE) before electrophysiological procedures in anticoagulated patients is variable. Our objective was to determine the incidence and identify predictors of intracardiac left atrial appendage (LAA) thrombus on TEE in patients with AF/AFl before electrical cardioversion or ablation. METHODS: We reviewed TEEs of 401 patients undergoing an electrical cardioversion, AF, or AFl ablation from April 2013 to September 2015 at the McGill University Health Center. Clinical and echocardiographic variables were collected at the time of the TEE and follow-up visits. Multivariate logistic regression was used to determine predictors of LAA thrombus. RESULTS: Of 401 patients, 11.2% had LAA thrombus on TEE. The majority (87%) of patients were anticoagulated for at least 3 weeks before the TEE. The incidence of LAA thrombus was 21% (23/110) in patients taking warfarin vs 6.4% (15/236) in patients taking direct oral anticoagulants. Multivariate analysis identified prior stroke (odds ratio [OR], 2.7; 95% confidence interval [CI], 1.1-6.9) and heart failure (OR, 2.2; 95% CI, 1.0-4.7) as predictors of thrombus, whereas direct oral anticoagulant use (OR, 0.4; 95% CI, 0.2-0.8) was associated with reduced odds of thrombus. CONCLUSIONS: LAA thrombus was identified in a significant proportion of patients undergoing TEE before cardioversion or ablation of AF/AFl despite preprocedural anticoagulation. Patients at increased risk of LAA thrombus (heart failure and prior stroke) may benefit from TEE before cardioversion, AF, or AFl ablation.

INTRODUCTION: La thromboembolie cérébrale est une complication potentiellement dévastatrice de la fibrillation auriculaire (FA) et du flutter auriculaire. L'utilisation de l'échocardiographie transœsophagienne (ETO) avant les interventions en électrophysiologie chez les patients anticoagulés est variable. Notre objectif était de déterminer la fréquence et les prédicteurs des thrombi intracardiaques dans l'appendice auriculaire gauche (AAG) à l'ETO chez les patients atteints de FA ou de flutter auriculaire avant de procéder à une cardioversion électrique ou à une ablation. MÉTHODES: Nous avons passé en revue les ETO de 401 patients qui avaient subi une cardioversion électrique, ou une ablation de la FA ou du flutter auriculaire entre avril 2013 et septembre 2015 au Centre universitaire de santé McGill. Nous avons recueilli les variables cliniques et échocardiographiques au moment de l'ETO et des visites de suivi. Nous avons utilisé la régression logistique multivariée pour déterminer les prédicteurs de thrombus dans l'AAG. RÉSULTATS: Parmi les 401 patients, 11,2 % avaient un thrombus dans l'AAG à l'ETO. La majorité (87 %) des patients étaient anticoagulés au moins 3 semaines avant l'ETO. La fréquence des thrombus dans l'AAG était de 21 % (23/110) chez les patients qui prenaient de la warfarine vs 6,4 % (15/236) chez les patients qui prenaient des anticoagulants oraux directs. L'analyse multivariée a permis d'établir que l'accident vasculaire cérébral (AVC) antérieur (ratio d'incidence approché [RIA], 2,7; intervalle de confiance [IC] à 95 %, 1,1-6,9) et l'insuffisance cardiaque (RIA, 2,2; IC à 95 %, 1,0-4,7) étaient des prédicteurs de thrombus, alors que l'utilisation d'anticoagulants oraux directs (RIA, 0,4; IC à 95 %, 0,2-0,8) était associée une probabilité moindre de thrombus. CONCLUSIONS: Une proportion importante de patients qui avaient subi l'ETO avant la cardioversion, ou l'ablation de la FA ou du flutter auriculaire avaient un thrombus dans l'AAG en dépit de l'anticoagulation avant l'intervention. Les patients exposés à un risque accru de thrombus dans l'AAG (insuffisance cardiaque et AVC antérieur) peuvent bénéficier de l'ETO avant la cardioversion, ou l'ablation de la FA ou du flutter auriculaire.

Risk Stratification of an Accessory Pathway Using Isoproterenol after Cardiac Arrest.

A 43-year-old man presented after ventricular fibrillation cardiac arrest with evidence of pre-excited atrial fibrillation. Electrophysiology study with guideline-directed testing demonstrated a low risk accessory pathway effective refractory period, which became high-risk with isoproterenol infusion. This case represents a challenging scenario wherein a high-risk pathway may be misclassified using the currently indicated methods of risk stratification.

Intracardiac echo-facilitated 3D electroanatomical mapping of ventricular arrhythmias from the papillary muscles: assessing the 'fourth dimension' during ablation.

AIMS: Ventricular arrhythmias (VA) originating from a papillary muscle (PM) have recently been described as a distinct clinical entity with peculiar features that make its treatment with catheter ablation challenging. Here, we report our experience using an intracardiac echo-facilitated 3D electroanatomical mapping approach in a case series of patients undergoing ablation for PM VA. METHODS AND RESULTS: Sixteen patients who underwent catheter ablation for ventricular tachycardia (VT) or symptomatic premature ventricular contractions originating from left ventricular PMs were included in the study. A total of 24 procedures (mean 1.5 per patient) were performed: 15 using a retrograde aortic approach and 9 using a transseptal approach. Integrated intracardiac ultrasound for 3D electroanatomical mapping was used in 15 of the 24 procedures. The posteromedial PM was the most frequent culprit for the clinical arrhythmia, and the body was the part of the PM most likely to be the successful site for ablation. The site of ablation was identified based on the best pace map matching the clinical arrhythmia and the site of earliest the activation. At a mean follow-up of 10.5 ± 7 months, only two patients had recurrent arrhythmias following a repeat ablation procedure. CONCLUSION: An echo-facilitated 3D electroanatomical mapping allows for real-time creation of precise geometries of cardiac chambers and endocavitary structures. This is useful during procedures such as catheter ablation of VAs originating from PMs, which require detailed representation of anatomical landmarks. Routine adoption of this technique should be considered to improve outcomes of PM VA ablation.

A Historical Perspective on the Role of Functional Lines of Block in the Re-entrant Circuit of Ventricular Tachycardia.

The ablation strategy for ventricular tachycardia (VT) rapidly evolved from an entrainment mapping approach for identification of the critical isthmus of the re-entrant circuit during monomorphic VT, toward a substrate-based approach aiming to ablate surrogate markers of the circuit during sinus rhythm in hemodynamically nontolerated and polymorphic VT. The latter approach implies an assumption that the circuits responsible for the arrhythmia are anatomical or fixed, and present during sinus rhythm. Accordingly, the lines of block delimiting the channels of the circuits are often considered fixed, although there is evidence that they are functional or more frequently a combination of fixed and functional. The electroanatomical substrate-based approach to VT ablation performed during sinus rhythm is increasingly adopted in clinical practice and often described as scar homogenization, scar dechanneling, or core isolation. However, whether the surrogate markers of the VT circuit during sinus rhythm match the circuit during arrhythmias remains to be fully demonstrated. The myocardial scar is a heterogeneous electrophysiological milieu with complex arrhythmogenic mechanisms that potentially coexist simultaneously. Moreover, the scar consists of different areas of diverse refractoriness and conduction. It can be misleading to limit the arrhythmogenic perspective of the myocardial scar to fixed or anatomical barriers held responsible for the re-entry circuit. Greater understanding of the role of functional lines of block in VT and the validity of the surrogate targets being ablated is necessary to further improve the technique and outcome of VT ablation.

Ablation of an atriofascicular accessory pathway with a zero-fluoroscopy procedure.

A 16-year-old patient with recurrent palpitations and documented left bundle branch block superior axis wide complex tachycardia underwent an electrophysiological study and ablation with a zero-fluoroscopy procedure. The electrophysiological study showed a decremental antegrade conducting atriofascicular pathway. Three-dimensional CARTO-guided mapping of the tricuspid annulus in sinus rhythm was performed, and a distinct signal corresponding to the accessory pathway potential of the atriofascicular pathway was found in the posterolateral region. By using an SR0 sheath and a 4-mm-tip catheter, radiofrequency application was delivered at this point on the annulus and successfully eliminated conduction through the accessory pathway.

A Systematic Review on the Progression of Paroxysmal to Persistent Atrial Fibrillation: Shedding New Light on the Effects of Catheter Ablation.

The progression from paroxysmal atrial fibrillation (AF) to persistent or long-term persistent forms has recently gained increasing attention. A growing amount of data has shown a significant morbidity and mortality associated with the transition. The aim of our systematic review was to assess the evidence regarding AF progression rates with different management approaches. Electronic databases were searched by using text words and relevant indexing to capture data on AF progression. Studies that considered progression from paroxysmal AF to a persistent or permanent form were included. The papers collected were divided into 2 groups: 1) general population studies (with almost exclusively medical therapy); and 2) studies that consider progression of AF subsequent to AF ablation. Twenty-one studies were included in the first group and 8 in the second group. In the first group, percentage of AF progression at 1 year ranged from 10% to 20%. Studies that included a longer follow-up detected a higher percentage of progression (from 50% to 77% after 12 years). In patients treated with catheter ablation, the percentage of progression was significantly lower (from 2.4% to 2.7% at 5 years' follow-up). The percentage of progression after catheter ablation did not change according to duration of follow-up. AF ablation is associated with significantly reduced progression to persistent forms compared with studies in the general population. Prevention of long-term AF progression may be a clinically relevant outcome after AF ablation. Further research is required to determine whether delaying progression of AF by catheter ablation reduces morbidity and mortality.

Managing novel oral anticoagulants in patients with atrial fibrillation undergoing device surgery: Canadian survey.

BACKGROUND: Approximately 10% of patients who undergo surgical procedures require chronic oral anticoagulation. Physicians must balance the thromboembolic and bleeding risks to make informed decisions on whether to continue anticoagulant medication. Evidence is lacking regarding the perioperative management of novel oral anticoagulant (NOAC) agents. This survey aims to describe the management of perioperative NOAC use during device implantation by Canadian centres. METHODS: A Web-based tool was used to survey all Canadian adult pacemaker/defibrillator implant centres. The survey collected data regarding the perioperative management of NOACs in atrial fibrillation patients at high risk for thromboembolism who undergo device implantation. RESULTS: Twenty-two centres performed approximately 14,971 device implants; 1150 (8%) of these implants were in patients who were prescribed a NOAC. In 82% of centres, the NOAC is discontinued in anticipation of device implantation; 73% of these centres do not bridge with heparin. In patients with normal renal function at high risk of thromboembolic events (Congestive Heart Failure, Hypertension, Age, Diabetes, Stroke/Transient Ischemic Attack; CHADS2 ≥ 2), 72% of the centres restart the NOAC within 48 hours of the procedure. For patients with abnormal renal function (glomerular filtration rate < 80 mL/min), the timing of NOAC discontinuation is variable. Hematoma rates vary from 0 to 30%. CONCLUSIONS: Most Canadian centres perform device implantation with NOAC interruption without the use of bridging. The timing of stopping and restarting anticoagulation and incidence of bleeding complications is variable. These findings emphasize the need for randomized controlled studies to guide the optimal approach to management of NOACs during device implantation.