Three-dimensional myocardial scar characterization from the endocardium: Usefulness of endocardial unipolar electroanatomic mapping

Epicardial ventricular arrhythmia ablation: a clinical consensus statement of the European Heart Rhythm Association of the European Society of Cardiology and the Heart Rhythm Society, the Asian Pacific Heart Rhythm Society, the Latin American Heart Rhythm Society, and the Canadian Heart Rhythm Society

Epicardial access during electrophysiology procedures offers valuable insights and therapeutic options for managing ventricular arrhythmias (VAs). The current clinical consensus statement on epicardial VA ablation aims to provide clinicians with a comprehensive understanding of this complex clinical scenario. It offers structured advice and a systematic approach to patient management. Specific sections are devoted to anatomical considerations, criteria for epicardial access and mapping evaluation, methods of epicardial access, management of complications, training, and institutional requirements for epicardial VA ablation. This consensus is a joint effort of collaborating cardiac electrophysiology societies, including the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, the Latin American Heart Rhythm Society, and the Canadian Heart Rhythm Society.

Ventricular tachycardia substrate mapping: What's been done and what needs to be done

Substrate mapping is an important component of electrophysiological (EP) study for the treatment of reentrant ventricular tachycardia (VT). It is used to detect characteristics of the electrical circuit and, in particular, the location and properties of the central common pathway, aka the isthmus, where multiple circuit loops can coincide. Typically, reentrant circuits are single or double loop, but as the common pathway size increases, 4-loop patterns may emerge, consisting of 2 parallel isthmuses or a single isthmus with 4 loops. Arrhythmogenic substrate contains a mixture of scar, calcification, and fibrofatty regions blended with viable ventricular myocytes, which can slow conduction. It is identified in the EP laboratory in part by the presence of low-amplitude electrograms and a zone of uniform slow conduction resulting from a sparsity of remaining viable myocytes and molecular-level remodeling. The electrograms recorded near isthmus boundaries frequently exhibit an abnormal morphology, such as fractionation and late or split deflections, due to the separation of muscle fiber bundles by fibroadipose tissue or calcification, and due to other conduction impediments such as source-sink mismatch, wherein topographic changes to the viable myocardial structure occur. Substrate mapping facilitates the identification of arrhythmogenic regions during sinus rhythm, whereas inducible VT with periods of ongoing reentry, when recordable, can be used for further assessment. Substrate modeling augments substrate mapping by seeking to predict electrogram morphology and mapped features and properties to be encountered during EP study based on an accurate depiction of arrhythmogenic tissue. Herein, we elaborate on the details of VT substrate mapping and modeling to the present time.

Unipolar Voltage Mapping to Predict Recovery of Left Ventricular Ejection Fraction in Patients With Recent-Onset Nonischemic Cardiomyopathy

BACKGROUND

The ability to predict recovery of left ventricular ejection fraction (LVEF) in response to guideline-directed therapy among patients with nonischemic cardiomyopathy is desired. We sought to determine whether left ventricular endocardial unipolar voltage measured during invasive electroanatomic mapping could be used to predict LVEF recovery among those with recent-onset nonischemic cardiomyopathy.

METHODS

We analyzed the left ventricular voltage maps of patients included in the eMAP trial (Electrogram-Guided Myocardial Advanced Phenotyping; NCT03293381), a prospective, nonrandomized, interventional trial conducted at 2 institutions between 2017 and 2020. Patients had recent-onset nonischemic cardiomyopathy defined by LVEF ≤45% and development of symptoms or signs of heart failure within the past 6 months. Detailed voltage maps of the left ventricular endocardium were generated using the Carto electroanatomic mapping system. Abnormal unipolar amplitude was defined as <8.27 mV. The primary end point was recovery of LVEF (Recovery) defined by a 1-year LVEF ≥50% or ≥45% with ≥10% increase from baseline.

RESULTS

Of the 29 enrolled patients (median age, 49 years [25th percentile, 39; 75th percentile, 59], 8 females [27.6%]), LVEF recovered in 13 (44.8%) by 1-year follow-up. The percentage of total endocardial surface area with unipolar voltage abnormality (AUA) was significantly lower among Recovery patients than No Recovery patients (18.2% [25th percentile, 6.4; 75th percentile, 22.4] versus 80.0% [25th percentile, 29.5; 75th percentile, 90.9]; P=0.004). Percent AUA was associated with lower likelihood of Recovery (odds ratio, 0.64 per 10% increase in AUA; 95% CI, 0.47-0.88; P=0.006). A 28% cutoff value for percent AUA was 92% sensitive and 75% specific with an area under the receiver operating characteristic curve of 0.81 (95% CI, 0.63-0.99; P=0.001) for predicting recovery versus no recovery. The majority of patients (12 of 13; 92.3%) with a percent AUA >28% did not recover.

CONCLUSIONS

Left ventricular unipolar voltage abnormality is a potent predictor of LVEF recovery among patients recently diagnosed with nonischemic cardiomyopathy. Detailed left ventricular unipolar voltage mapping could therefore be used as a valuable prognostic tool in guiding treatment decisions.

Epicardial Ablation for Arrhythmogenic Disorders in Patients with Brugada Syndrome

Brugada syndrome (BrS) is an inherited arrhythmogenic disorder characterized by distinct electrocardiographic patterns and an increased risk of sudden cardiac death due to ventricular arrhythmias. Effective management of BrS is essential, particularly for high-risk patients with recurrent arrhythmias. While implantable cardioverter-defibrillator (ICD) is effective in terminating life-threatening arrhythmias, it does not prevent arrhythmia onset and can lead to complications such as inappropriate shocks. Epicardial ablation has emerged as a promising treatment option for patients with recurrent ventricular arrhythmias and frequent ICD interventions. This review examines the latest advancements in the management of Brugada syndrome, focusing on the role and rationale of epicardial ablation for the treatment of patients at risk of sudden cardiac death.

Prognostic value of electroanatomic-guided endomyocardial biopsy in patients with myocarditis, arrhythmogenic cardiomyopathy and non dilated left ventricular cardiomyopathy

A wide variety of non-invasive and invasive techniques for SCD risk stratification in non ischemic cardiomyopathy (NICM) have been proposed, including left ventricular (LV) ejection fraction, QRS duration, late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) and invasive electrophysiologic study with or without three-dimensional electroanatomic mapping (3D-EAM), to identify and characterize the arrhythmogenic substrate. There is still no clear consensus on the risk stratification in this clinical setting. The aim of our study is to characterize the 3D-EAM substrate in patients with the same clinical presentation of unexplained complex VAs and NICM using CMR, three-dimensional electranatomic mapping (3D-EAM) in association with endomyocardial biopsy (EMB) and genetic screening, as a more precise and early diagnostic assessment may provide important subsequent prognostic impact. The study was designed as a prospective multi-center observational evaluation and the patient follow-up was scheduled at 6 months interval. We enrolled 125 patients distinct into four different group by complete diagnostic work-up: myocarditis, non-dilated left ventricular cardiomyopathy, arrhythmogenic cardiomyopathy and control group. The four groups were compared in terms of clinical, imaging and 3D-EAM data. At multivariate analysis sustained VT/VF on admission [HR: 3.64 (1.79-7.4), p < 0.001], total bipolar scar area of left and right ventricle detected by 3D-EAM [HR: 2.24 (1.13-4.49), p = 0.02], histological diagnosis of myocarditis by 3D-EAM guided endomyocardial biopsy (EBM) [HR: 2.79 (1.04-7.44), p = 0.01] were independent predictors of complex VAs or death at follow-up. 3D-EAM guided EMB represent not only a valid diagnostic tool to identify the arrhythmogenic substrate in patients with NICM and ventricular arrhythmic phenotype but also an important predictor of complex Vas at long term follow-up.

Unipolar voltage electroanatomic mapping detects structural atrial remodeling identified by LGE-MRI

BACKGROUND

In atrial fibrillation (AF) management, understanding left atrial (LA) substrate is crucial. While both electroanatomic mapping (EAM) and late gadolinium enhancement magnetic resonance imaging (LGE-MRI) are accepted methods for assessing the atrial substrate and are associated with ablation outcome, recent findings have highlighted discrepancies between low-voltage areas (LVAs) in EAM and LGE areas.

OBJECTIVE

The purpose of this study was to explore the relationship between LGE regions and unipolar and bipolar LVAs using multipolar high-density mapping.

METHODS

Twenty patients scheduled for AF ablation underwent preablation LGE-MRI. LA segmentation was conducted using a deep learning approach, which subsequently generated a 3-dimensional mesh integrating the LGE data. High-density EAM was performed in sinus rhythm for each patient. The electroanatomic map and LGE-MRI mesh were coregistered. LVAs were defined using cutoffs of 0.5 mV for bipolar voltage and 2.5 mV for unipolar voltage. The correspondence between LGE areas and LVAs in the LA was analyzed using confusion matrices and performance metrics.

RESULTS

A considerable 87.3% of LGE regions overlapped with unipolar LVAs, compared with only 16.2% overlap observed with bipolar LVAs. Across all performance metrics, unipolar LVAs outperformed bipolar LVAs in identifying LGE areas (precision: 78.6% vs 61.1%; sensitivity: 87.3% vs 16.2%; F1 score: 81.3% vs 26.0%; accuracy: 74.0% vs 35.3%).

CONCLUSION

Our findings demonstrate that unipolar LVAs strongly correlate with LGE regions. These findings support the integration of unipolar mapping alongside bipolar mapping into clinical practice. This would offer a nuanced approach to diagnose and manage AF by revealing critical insights into the complex architecture of the atrial substrate.

Mapping and Ablation of Ventricular Tachycardia in Inherited Left Ventricular Cardiomyopathies

Advances in the field of human genetics have led to an accumulating understanding of the genetic basis of distinct nonischemic cardiomyopathies associated with ventricular tachycardias (VTs) and sudden cardiac death. To date, there is an increasing proportion of patients with inherited cardiomyopathies requiring catheter ablation for VTs. This review provides an overview of disease-causing gene mutations frequently encountered and relevant for clinical electrophysiologists. Available data on VT ablation in patients with an inherited etiology and a phenotype of a nondilated left ventricular cardiomyopathy, dilated cardiomyopathy, or hypertrophic cardiomyopathy are summarized. VTs amenable to catheter ablation are related to nonischemic fibrosis. Recent insights into genotype-phenotype relations of subtype and location of fibrosis have important implications for treatment planning. Current strategies to delineate nonischemic fibrosis and related arrhythmogenic substrates using multimodal imaging, image integration, and electroanatomical mapping are provided. The ablation approach depends on substrate location and extension. Related procedural aspects including patient-tailored (enhanced) ablation strategies and outcomes are outlined. Challenging substrates for VT and the underlying inherited etiologies with a high risk for rapid progressive heart failure contribute to poor outcomes after catheter ablation. Electroanatomical data obtained during ablation may allow the identification of patients at particular risk who need to be considered for early work-up for left ventricular assist device implantation or heart transplantation.

Twenty-five years of research in cardiac imaging in electrophysiology procedures for atrial and ventricular arrhythmias

Catheter ablation is nowadays considered the treatment of choice for numerous cardiac arrhythmias in different clinical scenarios. Fluoroscopy has traditionally been the primary imaging modality for catheter ablation, providing real-time visualization of catheter navigation. However, its limitations, such as inadequate soft tissue visualization and exposure to ionizing radiation, have prompted the integration of alternative imaging modalities. Over the years, advancements in imaging techniques have played a pivotal role in enhancing the safety, efficacy, and efficiency of catheter ablation procedures. This manuscript aims to explore the utility of imaging, including electroanatomical mapping, cardiac computed tomography, echocardiography, cardiac magnetic resonance, and nuclear cardiology exams, in helping electrophysiology procedures. These techniques enable accurate anatomical guidance, identification of critical structures and substrates, and real-time monitoring of complications, ultimately enhancing procedural safety and success rates. Incorporating advanced imaging technologies into routine clinical practice has the potential to further improve clinical outcomes of catheter ablation procedures and pave the way for more personalized and precise ablation therapies in the future.

First clinical experience using a novel automated mapping algorithm for mapping of ventricular arrhythmias

A new automated vector-based mapping algorithm (AMA) for 3-dimensional (3D) mapping has been introduced. The aim of this study was to present our experience using AMA to recognize additional catheter ablation targets in patients with ventricular arrhythmias (VA). A total of 16 patients (ICM; ischemic cardiomyopathy, n = 6; NICM; non-ischemic cardiomyopathy n = 10) suffering from VA underwent catheter ablation. Following bipolar voltage mapping, AMA was utilized to reveal zones of decelerated conduction velocity vectors (CVV) and this information was superimposed onto the 3D reconstructions and compared with the presence of scar. Mapping time was 28.1 ± 10 min for the endocardial reconstruction of the left ventricle (LV) and 17 ± 5.4 min for the epicardium (n = 6 patients). The mean area of LV low voltage was 13.9 ± 15% (endocardial) and 11.9 ± 5.7% (epicardial). Decelerating CVV zones were revealed in all patients (mean conduction velocity threshold of 39.3 ± 13%). Sustained VA have been terminated through ablation and substrate modification was performed in all patients. Correlation between the presence of CVV deceleration zones and areas of abnormal low voltage from bipolar mapping was revealed in only 37.5% of patients, but there was good correlation between scar from unipolar voltage mapping and the presence of CCV deceleration zones (94%; p = 0.008). The novel AMA may improve the understanding of individual VA substrates due to the visualization of decelerated CVV zones and their correlation with abnormal low voltage predominantly from unipolar mapping.

Recurrent arrhythmic storms and unsuccessful catheter ablation in chronic ischemic heart disease

The prototypical substrate for reentrant ventricular tachycardia (VT) is post-myocardial infarction (MI) scar. Catheter ablation is an important therapeutic option for recurrent VT but sometimes it is not effective despite the technical advances. Here we describe the case of a 60-year-old man who suffered a MI in 1998 and presented with recurrent arrhythmic storms during his long-term follow-up. Twenty years later, he underwent two catheter ablations with bipolar electroanatomic voltage mapping (EVM) demonstrating only an area of low voltages in the lateral left ventricular free wall. Both procedures were unsuccessful and the patient eventually underwent cardiac transplantation in 2019. Pathology examination revealed circumferential subendocardial scar with hypertrabeculation, so that the reentry substrate was unreachable by ablation with the use of standard techniques. The comparison of EVM findings with the morphologic ones in patients with chronic ischemic heart disease can help to better understand the feasibility and effectiveness of VT substrate ablation.

Right ventricular outflow tract endocardial unipolar substrate mapping: implications in risk stratification of Brugada syndrome

Brugada syndrome (BrS) is a complex arrhythmogenic disease displaying electrical and micro-structural abnormalities mainly located at the epicardium of the right ventricular outflow tract (RVOT). It is well-known that fibrosis, fatty infiltration, inflammation and reduced gap junction expression have been demonstrated at the epicardial anterior aspect of the RVOT providing the arrhythmogenic substrate for ventricular arrhythmic events in BrS. A number of models have been proposed for the risk stratification of patients with BrS. Endocardial unipolar electroanatomical mapping is an emerging tool that has been reintroduced to identify and quantify epicardial electrical abnormalities. Interestingly, current findings correlate the presence of large-sized endocardial unipolar electroanatomical abnormalities with either ventricular fibrillation inducibility during programmed ventricular stimulation or symptom status. This review aims to present existing data about the role of endocardial unipolar electroanatomical mapping for the identification of RVOT epicardial abnormalities as well as its potential clinical implications in risk stratification of BrS.

Characterization of the electrophysiological substrate in patients with Barlow's disease

BACKGROUND

Myxomatous mitral valve prolapse (MVP) and mitral-annular disjunction (Barlow disease) are at-risk for ventricular arrhythmias (VA). Fibrosis involving the papillary muscles and/or the infero-basal left ventricular (LV) wall was reported at autopsy in sudden cardiac death (SCD) patients with MVP.

OBJECTIVES

We investigated the electrophysiological substrate subtending VA in MVP patients with Barlow disease phenotype.

METHODS

Twenty-three patients with VA were enrolled, including five with syncope and four with a history of SCD. Unipolar (Uni < 8.3 mV) and bipolar (Bi < 1.5 mV) low-voltage areas were analyzed with electro-anatomical mapping (EAM), and VA inducibility was evaluated with programmed ventricular stimulation (PES). Electrophysiological parameters were correlated with VA patterns, electrocardiogram (ECG) inferior negative T wave (nTW), and late gadolinium enhancement (LGE) assessed by cardiac magnetic resonance.

RESULTS

Premature ventricular complex (PVC) burden was 12 061.9 ± 12 994.6/24 h with a papillary-muscle type (PM-PVC) in 18 patients (68%). Twelve-lead ECG showed nTW in 12 patients (43.5%). A large Uni less than 8.3 mV area (62.4 ± 45.5 cm² ) was detected in the basal infero-lateral LV region in 12 (73%) patients, and in the papillary muscles (2.2 ± 2.9 cm² ) in 5 (30%) of 15 patients undergoing EAM. A concomitant Bi less than 1.5 mV area (5.0 ± 1.0 cm² ) was identified in two patients. A history of SCD, and the presence of nTW, and LGE were associated with a greater Uni less than 8.3 mV extension: (32.8 ± 3.1 cm² vs. 9.2 ± 8.7 cm² ), nTW (20.1 ± 11.0 vs. 4.1 ± 3.8 cm² ), and LGE (19.2 ± 11.7 cm² vs. 1.0 ± 2.0 cm² , p = .013), respectively. All patients with PM-PVC had a Uni less than 8.3 mV area. Sustained VA (ventricular tachycardia 2 and VF 2) were induced by PES only in four patients (one with resuscitated SCD).

CONCLUSIONS

Low unipolar low voltage areas can be identified with EAM in the basal inferolateral LV region and in the papillary muscles as a potential electrophysiological substrate for VA and SCD in patients with MVP and Barlow disease phenotype.

Sinus rhythm voltage fingerprinting in patients with mitral valve disease using a high-density epicardial mapping approach

Aims

Unipolar voltage (UV) mapping is increasingly used for guiding ablative therapy of atrial fibrillation (AF) as unipolar electrograms (U-EGMs) are independent of electrode orientation and atrial wavefront direction. This study was aimed at constructing individual, high-resolution sinus rhythm (SR) UV fingerprints to identify low-voltage areas and study the effect of AF episodes in patients with mitral valve disease (MVD).

Methods and results

Intra-operative epicardial mapping (interelectrode distance 2 mm) of the right and left atrium, Bachmann’s bundle (BB), and pulmonary vein area was performed in 67 patients (27 male, 67 ± 11 years) with or without a history of paroxysmal AF (PAF). In all patients, there were considerable regional variations in voltages. UVs at BB were lower in patients with PAF compared with those without [no AF: 4.94 (3.56–5.98) mV, PAF: 3.30 (2.25–4.57) mV, P = 0.006]. A larger number of low-voltage potentials were recorded at BB in the PAF group [no AF: 2.13 (0.52–7.68) %, PAF: 12.86 (3.18–23.59) %, P = 0.001]. In addition, areas with low-voltage potentials were present in all patients, yet we did not find any predilection sites for low-voltage potentials to occur.

Conclusion

Even in SR, advanced atrial remodelling in MVD patients shows marked inter-individual and regional variation. Low UVs are even present during SR in patients without a history of AF indicating that low UVs should carefully be used as target sites for ablative therapy.

Electrical Substrate Ablation for Refractory Ventricular Fibrillation: Results of the AVATAR Study

[Figure: see text].

Assessment of patients presenting with life-threatening ventricular arrhythmias and suspected myocarditis: The key role of endomyocardial biopsy

BACKGROUND

Life-threatening ventricular tachyarrhythmias (VAs) represent a significant cause of death in myocarditis.

OBJECTIVE

The purpose of this study was to identify predictors of sustained VAs in patients with myocarditis and ventricular phenotype diagnosed by workflow including endomyocardial biopsy (EMB) guided by 3D electroanatomic mapping (3D-EAM).

METHODS

We prospectively enrolled patients with suspected myocarditis and VAs, undergoing cardiac magnetic resonance imaging, coronary angiography, 3D-EAM, and EMB guided by 3D-EAM. At follow-up, sustained VAs were detected by device interrogation and 24-hour electrocardiographic Holter monitoring.

RESULTS

We enrolled 54 consecutive patients (mean age 41 ± 14 years; 32(59%) men) with normal ventricular function; left ventricular and right ventricular (RV) late gadolinium enhancement was present, respectively, in 21 (46%) and 6 (13%) of the 46 patients who underwent cardiac magnetic resonance. In 31 patients, the histological diagnosis was myocarditis, while in 14 patients, focal replacement myocardial fibrosis (FRMF); in 9 patients, specimens were inadequate (diagnostic yield of EMB 83%). 3D-EAM showed a larger endocardial scar area for both ventricles in myocarditis than in FRMF (RV bipolar mean scar area 22 ± 16 cm² vs 3 ± 2 cm²; P = .02; left ventricular bipolar mean scar area 13 ± 5 cm² vs 4 ± 2 cm²; P = .02, respectively). At a follow-up of 21 months, freedom from sustained VAs was 58% in myocarditis and 92% in FRMF (log-rank, P = .008). Histological diagnosis of myocarditis and RV endocardial scar were independent predictors of sustained VAs (P = .02 for both).

CONCLUSION

Our data highlight the need for 3D-EAM-guided EMB in apparently healthy young patients with suspected myocarditis and VAs.