Endocardial Fibroelastosis Resection: When it Works and When it Does Not.

Endocardial fibroelastosis (EFE) is a thickening of the endocardial layer by accumulation of collagen and elastic fibers. Endothelial to mesenchymal transformation is proposed to be the underlying mechanism of formation. Although EFE can occur in both right and left ventricles, this article will focus on management of left ventricular EFE. Through its fibrous, nonelastic manifestation EFE restricts the myocardium leading to diastolic and systolic ventricular dysfunction and prevents ventricular growth in neonates and infants. The presence of EFE may be a marker for underlying myocardial fibrosis as well. The extent of EFE within the left ventricular cavity can be variable ranging from patchy to confluent distribution. Similarly the depth of penetration and degree of infiltration into myocardium can be variable. The management of EFE is controversial, although resection of EFE has been reported as part of the staged ventricular recruitment therapy. Following resection, EFE recurs and infiltrates the myocardium after primary resection. Herein we review the current experience with EFE resection.

Effective ablation of atrial tachycardia with an epicardial circuit-insights from endocardial scars sites: a case study.

A previous study reported primary macroreentrant atrial tachycardia (AT) in the left atrium (LA), including the epicardial circuit on a left atrial anterior wall (LAAW) scar, without any prior cardiac intervention (Miyazawa et al. in J Cardiovasc Electrophysiol 2019; 30: 263-264). However, determining the target for terminating macroreentrant ATs is challenging. The mapping revealed a centrifugal pattern but did not fully elucidate the AT circuit. The reentrant mechanism of these ATs was confirmed using entrainment pacing. The earliest excitation site (EES) was traditionally selected as the ablation site, typically located in healthy tissue. However, our two cases provide new insights into AT termination, including the epicardial bridge across the endocardial LAAW scar, using minimum ablation points, without the need to ablate the healthy EES.

Intramyocardial Mapping of Ventricular Arrhythmias via Septal Venous Perforators: Defining the Superior Intraseptal Space.

Left ventricular outflow tract arrhythmias that fail endocardial mapping and ablation have traditionally been labeled as originating from the epicardial left ventricular summit. Although these sometimes can be targeted from the epicardial surface of the left ventricular ostium, such approach poses significant technical challenges. A significant proportion of such arrhythmias, however, exhibit intramyocardial origin, demonstrated by mapping intraseptal branches of the anterior interventricular vein, and henceforth defined as the basal superior intraseptal space.

Ambient circulation surrounding an ablation catheter tip affects ablation lesion characteristics.

INTRODUCTION: The association between ambient circulating environments (CEs) and ablation lesions has been largely underexplored. METHODS: Viable bovine myocardium was placed in a saline bath in an ex vivo endocardial model. Radiofrequency (RF) ablation was performed using three different ablation catheters: 3.5 mm open irrigated (OI), 4, and 8 mm. Variable flow rates of surrounding bath fluids were applied to simulate standard flow, high flow, and no flow. For in vivo epicardial ablation, 24 rats underwent a single OI ablation and performed with circulating saline (30 ml/min; n = 12), versus those immersed in saline without circulation (n = 12). RESULTS: High flow reduced ablation lesion volumes for all three catheters. In no-flow endocardial CE, both 4 mm and OI catheters produced smaller lesions compared with standard flow. However, the 8 mm catheter produced the largest lesions in a no-flow CE. Ablation performed in an in vivo model with CE resulted in smaller lesions compared with ablation performed in a no-flow environment. No statistically significant differences in steam pops were found among the groups. CONCLUSION: A higher endocardial CE flow can decrease RF effectiveness. Cardiac tissue subjected to no endocardial CE flow may also limit RF for 4 mm catheters, but not for OI catheters; these findings may have implications for RF ablation safety and efficacy, especially in the epicardial space without circulating fluid or in the endocardium under varying flow conditions.

Epicardial mapping and ablation of ventricular tachycardia from the coronary venous system in post-coronary bypass patients.

BACKGROUND: Ventricular tachycardia (VT) ablation of mid- or epicardial substrate is difficult and requires a creative approach in patients with a history of coronary bypass that precludes percutaneous epicardial catheter manipulation. The coronary venous system (CVS) provides limited access to the epicardial surface of the heart. The objective of this study is to assess the feasibility, safety, and efficacy of epicardial mapping and ablation of VT substrates from the CVS in patients with history of coronary bypass. METHODS: Patients undergoing VT ablation at our institution were retrospectively reviewed. Those who had basal to mid ventricular substrate based on computed tomography imaging and history of coronary bypass were included. Endocardial and CVS mapping and ablation was performed in standard fashion using 3D electroanatomic mapping. The primary endpoint was defined as VT circuit elimination, termination, non-inducibility, or perturbation of the circuit. RESULTS: Of 192 consecutive VT ablations from 2017 to 2020, 35 (18%) had a history of coronary bypass and basal to the mid-ventricular substrate by imaging. There were no significant characteristic differences between the endocardial only (n = 19) vs endocardial + CVS (n = 16) groups. In 14 (88%) of patients undergoing CVS mapping, the VT circuit was identified to be within access from the epicardial surface. Ablation was attempted in 8 (57%) of these patients, and the primary endpoint was reached in 88% of those undergoing CVS ablation. There were no complications related to CVS ablation. CONCLUSION: Mapping and ablation of mid- or epicardial VT circuits from the CVS branches are feasible and safe and may be helpful in the treatment of VT in patients who are otherwise not candidates for percutaneous epicardial ablation.

Techniques for Catheter Ablation of Idiopathic Ventricular Arrhythmias Originating from the Outflow Tract and Left Ventricular Summit.

Idiopathic ventricular arrhythmias (VAs) most commonly originate from the ventricular outflow tracts. Because the anatomy of this region is complex and some of those VA origins are intramural and epicardial, it may sometimes be difficult to locate the site of the VA origin. Meticulous mapping in multiple different locations such as the right and left ventricular outflow tracts, endocardial and epicardial sites, and above and below the aortic and pulmonic valves may be required to achieve successful catheter ablation of those VAs. Special ablation techniques may be considered to improve the outcome of catheter ablation of intramural and epicardial VAs.

Surgical Ablation of Ventricular Tachycardia.

Surgery for ventricular tachycardia (VT) is indicated in patients in whom pharmacotherapy or catheter ablation is ineffective or frequent VT attacks are not suppressed or with frequent activation of implantable cardioverter defibrillator. In ischemic VT, resection of fibrous endocardium combined with encircling cryothermia at the border between the infarcted and normal myocardium is performed. In surgery for VT associated with cardiomyopathy, close collaboration between the physician and surgeon is important and intraoperative mapping using electro-anatomic mapping system is helpful. In VT associated with cardiac tumors, cryothermia of the thinned subepicardial myocardium at the edge of the tumor is recommended in addition to resection of tumors.

Talk like a duck, walk like a duck: A cardiac surgeon's understanding of complex imaging in the management of atrial fibrillation.

The treatment of atrial fibrillation continues to evolve. The Heart Team Hybrid Ablation Approach is the latest iteration of Electrophysiology and Arrythmia surgeon collaboration that is focused on the treatment of complex (persistent and long-standing persistent) atrial fibrillation patients. Critical to this team approach is the ability to converse regarding atrial anatomy, atrial substrate and transmurality of ablation lesions. The cornerstone of these dialogs is advanced imaging techniques including; transesophageal echocardiography, enhanced magnetic resonance imaging, endocardial voltage mapping, and epicardial electrogram mapping. We herein review these techniques and their clinic implications.

Endocardial ablation at the mitral valve vestibule and its surroundings for the treatment of arrhythmias linked to the greater cardiac vasculature.

BACKGROUND: The role of the epicardial vasculature in supraventricular and ventricular arrhythmias was described in clinical studies as well as its treatment by intravascular point ablation or alcohol injection. We report on a case series of patients with different arrhythmias linked to an epicardial site of origin with evidence supporting transmural extensions that were targeted for ablation with successful outcomes. METHODS: The records of patients who has catheter ablation for Supraventricular or Ventricular arrhythmias between 2015 and 2020 was searched for patients with (1) arrhythmias linked to the epicardial vasculature and (2) findings to support an endocardial connection to the epicardial vasculature by activation mapping, pace mapping, or differential pacing, and (3) were successfully ablated via an endocardial approach only. RESULTS: From the data searched, we identified five patients with the following arrhythmias left ventricular summit ectopy, peri-mitral atrial flutter, preexcitation with inducible atrioventricular reentry tachycardia (AVRT), and a concealed left side accessory pathway with inducible AVRT that were linked to the following vessels: Great Cardiac vein, persistent left superior vena cava, left coronary cusp, and left ventricular outflow tract. Endocardial connections were supported by a combination of electro anatomical activation mapping, pace-mapping, and differential pacing. Endocardial ablations performed in all patients were successful without complications. CONCLUSION: This report highlights a subset of patients with arrhythmias linked to the greater cardiac vascular system that can be safely and effectively ablated endocardially, given the limitations and possible complications of epicardial ablation within or in the proximity of the epicardial vasculature.

Pulsed Field Ablation of the Porcine Ventricle Using a Focal Lattice-Tip Catheter.

BACKGROUND: Our understanding of catheter-based pulsed field ablation (PFA) of the ventricular myocardium is limited. We conducted a series of exploratory evaluations of ventricular PFA in swine ventricles. METHODS: A focal lattice-tip catheter was used to deliver proprietary biphasic monopolar PFA applications to swine ventricles under general anesthesia, with guidance from electroanatomical mapping, fluoroscopy, and intracardiac echocardiography. We conducted experiments to assess the impact of (1) delivery repetition (2×, 3×, or 4×) at each location, (2) epicardial PFA delivery, and (3) confluent areas of shallow healed endocardial scar created by prior PFA (4 weeks earlier) on subsequent endocardial PFA. Additional assessments included PFA optimized for the ventricle, lesion visualization by intracardiac echocardiography imaging, and immunohistochemical insights. RESULTS: Experiment no. 1: lesions (n=49) were larger with delivery repetition of either 4× or 3× versus 2×: length 17.6±3.9 or 14.2±2.0 versus 12.7±2.0 mm (P<0.01, P=0.22), width 13.4±1.8 or 10.6±1.3 versus 10.5±1.1 mm (P<0.01, P=1.00), and depth 6.1±2.1 or 5.1±1.3 versus 4.2±1.0 mm (P<0.01, P=0.21). Experiment no. 2: epicardial lesions (n=18) were reliably created and comparable to endocardial lesions: length 24.6±9.7 mm (n=5), width 15.6±4.6 mm, and depth 4.5±3.7 mm. Experiment no. 3: PFA (n=16) was able to penetrate to a depth of 4.8 (interquartile range, 4.5-5.4) mm in healthy myocardium versus 5.6 (interquartile range, 3.6-6.6) mm in adjacent healed endocardial scar (P=0.79), suggesting that superficial scar does not significantly impair PFA. Finally, we demonstrate, PFA optimized for the ventricle yielded adequate lesion dimensions, can result in myocardial activation, can be visualized by intracardiac echocardiography, and have unique immunohistochemical characteristics. CONCLUSIONS: This in vivo evaluation offers insights into the behavior of endocardial or epicardial PFA delivered using the lattice-tip catheter to normal or scarred porcine ventricular myocardium, thereby setting the stage for future clinical studies.

Hybrid convergent ablation versus endocardial catheter ablation for atrial fibrillation: a systematic review and meta-analysis of randomised control trials and propensity matched studies.

INTRODUCTION: Atrial fibrillation (AF) is the most common arrhythmia. Hybrid convergent ablation (HCA) is an emerging procedure for treating longstanding AF with promising results. HCA consists of a subxiphoid, surgical ablation followed by completion endocardial ablation. This meta-analysis of randomized control trials (RCT's) and propensity score-matched studies aims to examine the efficacy and safety of HCA compared to endocardial catheter ablation (ECA) alone on patients with AF. METHODS: This review was written in accordance with preferred reporting items for systematic reviews and meta-analyses recommendations and guidance. The primary outcome for the analysis was freedom from AF (FFAF) at final follow up. Secondary outcomes were mortality and significant complications such as tamponade, sternotomy, esophageal injury, atrio-esophageal fistulae post procedurally. RESULTS: Four studies where included, with a total of 233 patients undergoing HCA and 189 patients undergoing ECA only. Pooled analysis demonstrated that HCA cohorts had significantly higher rates of FFAF than ECA cohorts, with an OR of 2.78 (95% CI 1.82-4.24, P < 0.01, I2 = 0). Major post-operative complications were observed in significantly more patients in the HCA group, with an OR of 5.14 (95% CI 1.70-15.54, P < 0.01). There was only one death reported in the HCA cohorts, with no deaths in the ECA cohort. CONCLUSION: HCA is associated with a significantly higher FFAF than ECA, however, it is associated with increased post-procedural complications. There was only one death in the HCA cohort. Large RCT's comparing the HCA and ECA techniques may further validate these results.

How to use pace mapping for ventricular tachycardia ablation in postinfarct patients.

We aim to describe the technical aspects of pace mapping (PM), as well as the two typical patterns of pacing correlation maps during ventricular tachycardia (VT) ablation. The first main pattern is focal, with a gradual and eccentric decrease of the QRS correlation from the area with the best PM correlation. This focal pattern may be associated with two clinical situations: (1) with some endocardial points showing a good correlation compared to VT morphology: true endocardial exit of VT or endocardial breakthrough of either an intramural or an epicardial circuit; (2) without any endocardial points showing a good correlation compared to VT morphology: the VT may originate from the other ventricle, but the presence of an intramural or an epicardial circuit should be considered in patients with a structural heart disease. The second pattern is the presence of PM points exhibiting a good correlation close to other PM points showing a poor correlation compared to VT morphology: this abrupt change in paced QRS morphology over a short distance indicates divergence of activation wavefronts between these sites and suggests the presence of a slow conduction channel: the VT isthmus.

[Anatomy of the left ventricle for endocardial ablation]. / Anatomie des linken Ventrikels als Grundlage für endokardiale Ablationen.

As with all cardiac interventions, performing left ventricular ablation requires profound knowledge of cardiac anatomy. The aim of this article is to provide an overview of left ventricular anatomy and to characterize complex and clinically relevant structures from an electrophysiologist-centered perspective. In addition to the different access routes, the trabecular network, the left ventricular outflow tract, and the left ventricular conduction system, complex anatomical structures such as the aortomitral continuity and the left ventricular summit are also explained. In addition, this article offers multiple clinical examples that combine ECG, anatomy, and electrophysiologic study.

Combined epicardial and endocardial approach for redo radiofrequency catheter ablation in patients with persistent atrial fibrillation: a randomized clinical trial.

AIMS: An epicardial approach is an effective means to detect and eliminate residual potentials in non-transmural lesions created during prior endocardial ablation. We sought to determine the impact of a combined epicardial and endocardial approach compared with a conventional endocardial approach, on recurrence-free survival after redo ablation. METHODS AND RESULTS: Participants with recurred persistent atrial fibrillation after prior endocardial ablation were randomized (1:1) to undergo treatment with the combined approach (epicardial followed by endocardial ablation) for the treatment group or conventional approach (endocardial ablation only) for the control group. The primary outcome was the time to recurrence of atrial fibrillation or atrial tachycardia following a 90-day blanking period within 12 months after the procedure. The secondary safety outcome was the occurrence of procedure-related complications within 24 h after the procedure. Of 100 randomized participants {median age, 59.0 [(interquartile range (IQR): 53.8-64.3] years, including 16% women, with one prior ablation (IQR: 1-1)}, 93 (93%) completed the trial. Events relevant to the primary outcome occurred in 16 patients in the treatment group and in 21 patients in the control group {Kaplan-Meier estimator percentages, 32 vs. 42%; hazard ratio, 0.71 [95% confidence interval (CI): 0.37-1.37]}. The periprocedural complication rate was lower in the treatment group [2 vs. 16%; odds ratio, 0.11 (95% CI: 0.00-0.87)] with similar achievement of the procedural endpoint in the two groups. CONCLUSION: In the redo procedure for persistent atrial fibrillation, the combined approach had no significant difference of recurrence-free survival and a lower procedural complication rate compared with the conventional approach.

Utility of Prolonged Duration Endocardial Ablation for Ventricular Arrhythmias Originating From the Left Ventricular Summit.

OBJECTIVES: This study sought to explore whether prolonged duration (PD) radiofrequency ablation (RFA) from adjacent endocardial locations can improve catheter ablation (CA) outcomes of left ventricular summit (LVS) ventricular arrhythmias (Vas). BACKGROUND: CA of VAs originating from the LVS region can be challenging. METHODS: Patients undergoing CA of LVS VAs from January 1, 2015, to December 31, 2019, were included. Standard RFA approach involved incremental power titration (20-45 W) over 60-120 seconds with irrigated tip catheter to achieve 10%-12% impedance drop. Prolonged duration RFA involved similar power titration; however, lesion application was extended beyond 120 seconds (maximum 5 minutes). Lesions were confined to lowest aspect of aortic cusps and/or subvalvular LV outflow tract region (≤0.5 cm from the valve). Procedural success was defined as suppression of VA ≥30 minutes postablation and clinical success as no arrhythmia symptoms on follow-up and >80% reduction of VA burden on postprocedure monitor. RESULTS: This study included 102 patients (60±14 years old, 62% male): standard RFA in 80 and PD RFA in 38. Procedural success was achieved in 54 patients with standard and 32 patients with PD RFA (68% vs 84%; P = 0.05). Short-term clinical success was achieved in 48 patients (60%) with standard and 30 patients (79%) with PD RFA (P = 0.04). Two pericardial effusions occurred (1 in each group) and no steam pops were noted. Patients in whom standard RFA was successful were more likely to have R/S ratio >1 or absence of qS in lead I (odds ratio: 3.35; 95% CI: 1.20-9.35; P = 0.03). CONCLUSIONS: Prolonged duration RFA from adjacent endocardial locations is a safe and effective technique for successfully targeting challenging LVS VAs that fail standard RFA.

Endocardial Scar-Homogenization With vs Without Epicardial Ablation in VT Patients With Ischemic Cardiomyopathy.

OBJECTIVES: In this study, the authors investigated the ablation success of scar homogenization with combined (epicardial + endocardial) vs endocardial-only approach for ventricular tachycardia (VT) in patients with ischemic cardiomyopathy (ICM) at 5 years of follow-up. BACKGROUND: Best ablation approach to achieve long-term success rate in VT patients with ICM is not known yet. METHODS: Consecutive ICM patients undergoing VT ablation at our center were classified into group 1: endocardial + epicardial scar homogenization and group 2: endocardial scar homogenization. Patients with previous open heart surgery were excluded. Epicardial ablation was performed despite being noninducible after endocardial ablation in all group 1 patients. All patients underwent bipolar substrate mapping with standard scar settings defined as normal tissue >1.5 mV and severe scar <0.5 mV. Noninducibility of monomorphic VT was the procedural endpoint in both groups. Patients were followed up every 4 months for 5 years with implantable device interrogations. RESULTS: A total of 361 patients (group 1: n = 70 and group 2: n = 291) were included in the study. At 5 years, 81.4% (n = 57/70) patients from group 1 and 66.3% (n = 193/291) from group 2 were arrhythmia-free (P = 0.01) Of those patients, 26 of 57 (45.6%) and 172 of 193 (89.1%) from group 1 and group 2 respectively were on anti-arrhythmic drugs (AAD) (log-rank P < 0.001). After adjusting for age, sex, and obstructive sleep apnea, endo-epicardial scar homogenization was associated with a significant reduction in arrhythmia-recurrence (HR: 0.48; 95% CI: 0.27-0.86; P = 0.02). CONCLUSIONS: In this series of patients with ICM and VT, epicardial substrate was detected in all group 1 patients despite being noninducible after endocardial ablation. Moreover, combined endo-epicardial scar homogenization was associated with a significantly higher success rate at 5 years of follow-up and a substantially lower need for antiarrhythmic drugs after the procedure compared with the endocardial ablation alone.

Study on the effect of different blood flow velocities of pulmonary vein on endocardial microwave ablation of atrial fibrillation.

OBJECTIVE: To cure atrial fibrillation, the maximum ablation depth (⩾ 50∘C) should exceed the myocardial thickness to achieve the effect of transmural ablation. The blood flow of pulmonary vein in the endocardium can cause the change in the myocardial temperature distribution. Therefore, the study investigated the effect of different pulmonary vein blood flow velocities on the endocardial microwave ablation. METHODS: The finite element model of the endocardial microwave ablation of pulmonary vein was simulated by electromagnetic thermal flow coupling. The ablation power was 30 W and the ablation time was within 30 s. The blood flow in the coupling of fluid mechanics equation and heat transfer equation results in the heat damage. Furthermore, the cause of the different lesion dimensions is the blood flow velocity. The flow velocities were set as 0, 0.02, 0.05, 0.07, 0.12, 0.16, 0.20, 0.25 and 0.30 m/s. RESULTS: When the flow velocities were 0, 0.02, 0.05, 0.07, 0.12, 0.16, 0.20, 0.25 and 0.30 m/s, the maximum ablation depth were 6.00, 5.56, 5.16, 5.12, 5.04, 5.01, 4.98, 4.96 and 4.94 mm, respectively; the maximum ablation width were 12.53, 9.63, 9.23, 9.16, 9.07, 9.05, 8.94, 8.91 and 8.90 mm, respectively; the maximum ablation length were 12.00, 11.61, 8.98, 8.59, 8.37, 8.23, 8.16, 8.06 and 8.04 mm respectively. To achieve transmural ablation, the time was 3, 3, 3, 3, 3, 4, 4, 4, 4 s, respectively when the myocardial thickness was 2 mm; the time was 7, 8, 8, 8, 9, 9, 9, 9, 9 s, respectively when 3 mm; the time was 15, 16, 18, 19, 19, 20, 20, 20, 20 s, respectively when 4 mm. CONCLUSIONS: When the velocity increases from 0 m/s to 0.3 m/s, the microwave lesion depth decreases by 1.06 mm. To achieve transmural ablation, when the myocardial thickness is 2 mm, 3 and 4 s should be taken when the velocity is 0-0.12 and 0.12-0.30 m/s, respectively; when the myocardial thickness is 3 mm, 7, 8 and 9 s should be taken when 0, 0-0.07 and 0.07-0.30 m/s respectively; when the myocardial thickness is 4 mm, 15, 16, 18, 19, 20 s should be taken when 0, 0-0.02, 0.02-0.05, 0.05-0.12, 0.12 m/s-0.30 m/s.