Substrate Characterization and Outcomes of Ventricular Tachycardia Ablation in Titin Cardiomyopathy: A Multicenter Study

Titin Cardiomyopathy Associated With Refractory Ventricular Tachycardia: A Case Report

Cardiomyopathy is defined as structural and functional myocardial abnormality not attributed to ischemic, valvular, hypertensive, or congenital cardiac causes. The main phenotypes of cardiomyopathy include hypertrophic, dilated, non-dilated left ventricular, restrictive, arrhythmogenic right ventricular, Takotsubo, and left ventricular noncompaction cardiomyopathies. A significant proportion of dilated cardiomyopathy (DCM) cases represents patients with genetic mutations, most commonly titin gene truncating variants (TTNtv). It has been shown that TTNtv mutation contributes to the development of certain types of DCM such as alcohol, chemotherapy, and peripartum. We present a case of DCM where genetic workup revealed TTNtv without other contributing factors. The course was complicated by multiple ventricular tachycardias (VTs) refractory to medical management, despite treatment with amiodarone, sotalol, dofetilide, mexiletine, and propranolol. Interestingly, endocardial mapping failed to delineate the substrate of tachycardia. This report underscores the importance of genetic testing in DCM and highlights the potential association of titin cardiomyopathy with refractory VTs, possibly of epicardial origin.

Exploring TTN variants as genetic insights into cardiomyopathy pathogenesis and potential emerging clues to molecular mechanisms in cardiomyopathies

The giant protein titin (TTN) is a sarcomeric protein that forms the myofibrillar backbone for the components of the contractile machinery which plays a crucial role in muscle disorders and cardiomyopathies. Diagnosing TTN pathogenic variants has important implications for patient management and genetic counseling. Genetic testing for TTN variants can help identify individuals at risk for developing cardiomyopathies, allowing for early intervention and personalized treatment strategies. Furthermore, identifying TTN variants can inform prognosis and guide therapeutic decisions. Deciphering the intricate genotype-phenotype correlations between TTN variants and their pathologic traits in cardiomyopathies is imperative for gene-based diagnosis, risk assessment, and personalized clinical management. With the increasing use of next-generation sequencing (NGS), a high number of variants in the TTN gene have been detected in patients with cardiomyopathies. However, not all TTN variants detected in cardiomyopathy cohorts can be assumed to be disease-causing. The interpretation of TTN variants remains challenging due to high background population variation. This narrative review aimed to comprehensively summarize current evidence on TTN variants identified in published cardiomyopathy studies and determine which specific variants are likely pathogenic contributors to cardiomyopathy development.

Catheter Ablation for Ventricular Tachycardia in Patients With Desmoplakin Cardiomyopathy

BACKGROUND

Desmoplakin (DSP) pathogenic/likely pathogenic (P/LP) variants are associated with malignant phenotypes of arrhythmogenic cardiomyopathy (DSP-ACM). Reports of outcomes after ventricular tachycardia (VT) ablation in DSP-ACM are scarce.

OBJECTIVES

In this study, the authors sought to report on long-term outcomes of VT ablation in DSP-ACM.

METHODS

Patients with P/LP DSP variants at 9 institutions undergoing VT ablation were included. Demographic, clinical, and instrumental data as well as all ventricular arrhythmia (VA) events were collected. Sustained VAs after the index procedure were the primary outcome. A per-patient before and after ablation comparison of rates of VA episodes per year was performed as well.

RESULTS

Twenty-four DSP-ACM patients (39.3 ± 12.1 years of age, 62.5% male, median 6,116 [Q1-Q3: 3,362-7,760] premature ventricular complexes [PVCs] per 24 hours, median 4 [Q1-Q3: 2-11] previous VA episodes per patient at ablation) were included. Index procedure was most commonly endocardial/epicardial (19/24) The endocardium of the right ventricle (RV), the left ventricle (LV), or both ventricles were mapped in 8 (33.3%), 9 (37.5%), and 7 (29.2%) cases, respectively. Low voltage potentials were found in 10 of 15 patients in the RV and 11 of 16 in the LV. Endocardial ablation was performed in 18 patients (75.0%). Epicardial mapping in 19 patients (79.2%) identified low voltage potentials in 17, and 16 received epicardial ablation. Over the following 2.9 years (Q1-Q3: 1.8-5.5 years), 13 patients (54.2%) experienced VA recurrences. A significant reduction in per-patient event/year before and after ablation was observed (1.4 [Q1-Q3: 0.5-2.4] to 0.1 [Q1-Q3: 0.0-0.4]; P = 0.009). 2 patients needed heart transplantation, and 4 died (3 of heart failure and 1 noncardiac death).

CONCLUSIONS

VT ablation in DSP-ACM is effective in reducing the VA burden of the disease, but recurrences are common. Most VT circuits are epicardial, with both LV and RV low voltage abnormalities. Heart failure complicates clinical course and is an important cause of mortality.

Ventricular Tachycardia Ablation in Patients With Desmoplakin Cardiomyopathy

BACKGROUND

Desmoplakin (DSP) pathogenic variants are rare causes of arrhythmogenic cardiomyopathy and often involve the right and left ventricles. Ventricular tachycardia (VT) ablations may be required in these patients, but procedural characteristics have not been reported.

OBJECTIVES

In this study, the authors sought to report a multicenter experience of VT ablation in patients with DSP pathogenic variants.

METHODS

VT ablations performed in patients with known DSP pathogenic variants were analyzed across 6 centers in 3 countries. Patient characteristics and acute and long-term procedural outcomes were reported.

RESULTS

A total of 20 patients (13 men, median age 43 years [Q1-Q3: 41.5-53.0 years], left ventricular ejection fraction 43.0% [Q1-Q3: 41.5%-53.0%], 11 previous failed ablations) were referred for VT ablation procedures. All patients had symptomatic VTs, with ICD therapy in 19 patients. Epicardial procedures were performed in 16 of the 20 patients. VT target sites were located in the right ventricular (RV) endocardium (n = 11), the RV epicardium (n = 4), the left ventricular (LV) endocardium (n = 2) and the LV epicardium (n = 7). In 3 patients, the VT target sites were in close proximity to coronary arteries, limiting ablation. During follow-up, VTs recurred in 11 patients, and repeated ablations were performed in 9 patients. Allowing for multiple procedures, 19 of the 20 patients remained free of VT recurrence after a median follow-up of 18 months [Q1-Q3: 5-60 months].

CONCLUSIONS

Patients with DSP cardiomyopathy often have biventricular involvement, and ablation procedures often require ablation in both ventricles and the epicardium. Recurrences are not uncommon, and the pathologic substrate can be located in close proximity to epicardial coronary arteries, limiting the success rate of ablations.

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.

Associations of MYPN, TTN, SCN5A, MYO6 and ELN Mutations With Arrhythmias and Subsequent Sudden Cardiac Death: A Case Report of an Ecuadorian Individual

Cardiac pathologies are among the most frequent causes of death worldwide. Regarding cardiovascular deaths, it is estimated that 5 million cases are caused by sudden cardiac death (SCD) annually. The primary cause of SCD is ventricular arrhythmias. Genomic studies have provided pathogenic, likely pathogenic, and variants of uncertain significance that may predispose individuals to cardiac causes of sudden death. In this study, we describe the case of a 43-year-old individual who experienced an episode of aborted SCD. An implantable cardioverter defibrillator was placed to prevent further SCD episodes. The diagnosis was ventricular fibrillation. Genomic analysis revealed some variants in the MYPN (pathogenic), GCKR (likely pathogenic), TTN (variant of uncertain significance), SCN5A (variant of uncertain significance), MYO6 (variant of uncertain significance), and ELN (variant of uncertain significance) genes, which could be associated with SCD episodes. In addition, a protein-protein interaction network was obtained, with proteins related to ventricular arrhythmia and the biological processes involved. Therefore, this study identified genetic variants that may be associated with and trigger SCD in the individual. Moreover, genetic variants of uncertain significance, which have not been reported, could contribute to the genetic basis of the disease.

Value of genotyping and scar-phenotyping for VT ablation procedures in patients with nonischemic left ventricular cardiomyopathies

INTRODUCTION

Variants of cardiomyopathy genes in patients with nonischemic cardiomyopathy (NICM) generate various phenotypes of cardiac scar and delayed enhancement cardiac magnetic resonance (DE-CMR) imaging which may impact ventricular tachycardia (VT) management.

METHODS

The objective was to compare the findings of cardiomyopathy genetic testing on DE-CMR imaging and long-term outcomes among patients with NICM undergoing VT ablation procedures. Image phenotyping and genotyping were performed in a consecutive series of patients referred for VT ablation and correlated to survival free of VT. Scar depth index (SDI) (% of scar at 0-3 mm, 3-5 mm and >5 mm projected on the closest endocardial surface) was determined.

RESULTS

Forty-three patients were included (11 women, 55 ± 14 years, ejection fraction (EF) 45 ± 16%) and were followed for 3.4 ± 2.9 years. Pathogenic variants (PV) were identified in 16 patients (37%) in the following genes: LMNA (n = 5), TTN (n = 5), DSP (n = 2), AMLS1 (n = 1), MYBPC3 (n = 1), PLN (n = 1), and SCN5A (n = 1). A ring-like septal scar (RLSS) pattern was more often seen in patients with pathogenic variants (66% vs 15%, p = .001). RLSS was associated with deeper seated scars (SDI >5 mm 30.6 ± 22.6% vs 12.4 ± 16.2%, p = .005), and increased VT recurrence (HR 5.7 95% CI[1.8-18.4], p = .003). After adjustment for age, sex, EF, and total scar burden, the presence of a PV remained independently associated with worse outcomes (HR 4.7 95% CI[1.22-18.0], p = .02).

CONCLUSIONS

Preprocedural genotyping and scar phenotyping is beneficial to identify patients with a favorable procedural outcome. Some PVs are associated with an intramural, deeper seated scar phenotype and have an increase of VT recurrence after ablation.

[Recent studies on dilated cardiomyopathy caused by TTN mutations in children]

The mutations of TTN gene that encodes titin are the most common mutation type among the genetic causes of dilated cardiomyopathy (DCM). This article reviews the worldwide studies on potential molecular pathogenesis (transcription, post-translational modification, etc.), clinical phenotypes, and gene therapies of pediatric DCM caused by TTN mutations, with the hope of providing a reference for the precision treatment of pediatric DCM caused by TTN mutations.