Prevalence and Prognostic Impact of Pathogenic Variants in Patients With Dilated Cardiomyopathy Referred for Ventricular Tachycardia Ablation

Etiologies, Mechanisms, Management, and Outcomes of Electrical Storm

Electrical storm (ES) is characterized by three or more discrete sustained ventricular tachyarrhythmia episodes occurring within a limited time frame (generally ≤ 24 h) or an incessant ventricular tachyarrhythmia lasting > 12 h. In patients with an implantable cardioverterdefibrillator (ICD), ES is defined as three or more appropriate device therapies, separated from each other by at least 5 min, which occur within a 24-h period. ES may constitute a medical emergency, depending on the number arrhythmic episodes, their duration, the type, and the cycle length of the ventricular arrhythmias, as well as the underlying ventricular function. This narrative review was facilitated by a search of MEDLINE to identify peer-reviewed clinical trials, randomized controlled trials, meta-analyses, and other clinically relevant studies. The search was limited to English-language reports published between 1999 and 2023. ES was searched using the terms mechanisms, genetics, channelopathies, management, pharmacological therapy, sedation, neuraxial modulation, cardiac sympathetic denervation, ICDs, and structural heart disease. Google and Google scholar as well as bibliographies of identified articles were reviewed for additional references. This manuscript examines the current strategies available to treat ES and compares pharmacological and invasive treatment strategies to diminish ES recurrence, morbidity, and mortality.

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.

Pleomorphic Ventricular Tachycardia in Dilated Cardiomyopathy Predicts Ventricular Tachycardia Recurrence After Ablation Independent From Cardiac Function: Comparison With Patients With Ischemic Heart Disease

BACKGROUND

In dilated cardiomyopathy (DCM), outcome after catheter ablation of ventricular tachycardia (VT) is modest, compared with ischemic heart disease (IHD). Pleomorphic VT (PL-VT) has been associated with fibrotic remodeling and end-stage heart failure in IHD. The prognostic role of PL-VT in DCM is unknown.

METHODS

Consecutive IHD (2009-2016) or DCM (2008-2018) patients undergoing ablation for monomorphic VT were included. PL-VT was defined as ≥1 spontaneous change of the 12-lead VT-morphology during the same induced VT episode. Patients were followed for VT recurrence and mortality.

RESULTS

A total of 247 patients (86% men; 63±13 years; IHD n=152; DCM n=95) underwent ablation for monomorphic VT. PL-VT was observed in 22 and 29 patients with IHD and DCM, respectively (14% versus 31%, P=0.003). In IHD, PL-VT was associated with lower LVEF (28±9% versus 34±12%, P=0.02) and only observed in those with LVEF<40%. In contrast, in DCM, PL-VT was not related to LVEF and induced in 27% of patients with LVEF>40%. During a median follow-up of 30 months, 79 (32%) patients died (IHD 48; DCM 31; P=0.88) and 120 (49%) had VT recurrence (IHD 59; DCM 61; P<0.001). PL-VT was associated with mortality in IHD but not in DCM. In IHD, VT recurrence was independently associated with LVEF, number of induced VTs, and procedural noncomplete success. Of note, in DCM, PL-VT (HR, 2.62 [95% CI, 1.47-4.69]), pathogenic mutation (HR, 2.13 [95% CI, 1.16-3.91]), and anteroseptal VT substrate (HR, 1.75 [95% CI, 1.00-3.07]) independently predicted VT recurrence.

CONCLUSIONS

In IHD, PL-VT was associated with low LVEF and mortality. In DCM, PL-VT was not associated with mortality but a predictor of VT recurrence independent from LVEF. PL-VT in DCM may indicate a specific arrhythmic substrate difficult to control by current ablation techniques.

Primary prevention implantable cardioverter-defibrillator use in non-ischemic dilated cardiomyopathy based on arrhythmic risk stratification and left ventricular reverse remodeling prediction

Sudden cardiac death (SCD) and significant ventricular arrhythmias in patients with dilated cardiomyopathy (DCM) have been markedly reduced over the last couple of decades as a result of the advances in pharmacological and non-pharmacological treatment. Primary prevention implantable cardioverter-defibrillator (ICD) plays an important role in the treatment of patients at risk of SCD caused by ventricular arrhythmias. However, the arrhythmic risk stratification in patients with DCM remains extremely challenging, and the decision for primary prevention ICD implantation based on left ventricular ejection fraction (LVEF) solely appears to be insufficient. This review provides an update on current evidence for primary prevention ICD implantation, arrhythmic risk stratification, and left ventricular reverse remodeling (LVRR) prediction in patients with DCM in addition to most recent guideline recommendations for primary prevention ICD implantation in DCM patients and a proposed multiparametric algorithm based on arrhythmic risk stratification and left ventricular reverse remodeling (LVRR) prediction to better identify patients who are likely to benefit from primary prevention ICD.

Genotype-Phenotype Correlations in Human Diseases Caused by Mutations of LINC Complex-Associated Genes: A Systematic Review and Meta-Summary

Mutations in genes encoding proteins associated with the linker of nucleoskeleton and cytoskeleton (LINC) complex within the nuclear envelope cause different diseases with varying phenotypes including skeletal muscle, cardiac, metabolic, or nervous system pathologies. There is some understanding of the structure of LINC complex-associated proteins and how they interact, but it is unclear how mutations in genes encoding them can cause the same disease, and different diseases with different phenotypes. Here, published mutations in LINC complex-associated proteins were systematically reviewed and analyzed to ascertain whether patterns exist between the genetic sequence variants and clinical phenotypes. This revealed LMNA is the only LINC complex-associated gene in which mutations commonly cause distinct conditions, and there are no clear genotype-phenotype correlations. Clusters of LMNA variants causing striated muscle disease are located in exons 1 and 6, and metabolic disease-associated LMNA variants are frequently found in the tail of lamin A/C. Additionally, exon 6 of the emerin gene, EMD, may be a mutation "hot-spot", and diseases related to SYNE1, encoding nesprin-1, are most often caused by nonsense type mutations. These results provide insight into the diverse roles of LINC-complex proteins in human disease and provide direction for future gene-targeted therapy development.

Long-Term Outcomes after Catheter Ablation of Ventricular Tachycardia in Dilated vs. Ischemic Cardiomyopathy

Ischemic (ICM) and dilated cardiomyopathy (DCM) represent the two main underlying heart diseases in patients referred for catheter ablation of ventricular tachycardia (VT). While VT ablation in ischemic cardiomyopathy is relatively well-studied, data in patients with DCM are still scarce. The study aimed to compare the acute and long-term outcomes in patients with ICM and DCM who underwent VT ablation at a high-volume center. Consecutive patients who underwent VT ablation from April 2018 to April 2021 were included retrospectively. Patients with ischemic cardiomyopathy were compared to those with dilated cardiomyopathy. The primary endpoint was rate of VT recurrences, the secondary endpoints included overall mortality, rehospitalization because of cardiac condition (VT, acute heart failure, acute myocardial infarction, heart transplantation or implantation of left ventricular assisting device), and major adverse cardiac events (MACE) at long-term follow-up. A total of 225 patients admitted for first VT ablation were included. A total of 156 patients (69%) revealed ICM and 69 (31%) DCM. After a mean follow-up of 22 months, the primary endpoint of VT recurrence occurred significantly more often in the patients with dilated cardiomyopathy (ICM n = 47; 37% vs. DCM n = 34; 64%; p = 0.001). In regard to the secondary endpoint of overall mortality, there was no difference between the two patient cohorts (DCM n = 9; 15% vs. ICM n = 22; 16%; p = 0.677); the patients with DCM showed significantly higher rehospitalization rates due to cardiac conditions (75% vs. 59%; p = 0.038) and more frequent MACE (68% vs. 52%; p= 0.036). In a Cox regression model, electrical storm at admission was shown to be a predictor for VT recurrence after successful catheter ablation (HR = 1.942: 95% CI 1.237–3.050; p = 0.004), while the ablation of every induced VT morphology during the procedure (HR = 0.522; 95% CI = 0.307–0.885; p = 0.016) contributed to a positive long-term outcome. DCM is associated with a higher risk of VT recurrence after catheter ablation compared to ICM. Furthermore, patients with DCM are more frequent re-hospitalized in the majority of cases due the VT recurrence. There is no difference in the long-term mortality between the two cohorts.

Arrhythmias as Presentation of Genetic Cardiomyopathy

There is increasing evidence regarding the prevalence of genetic cardiomyopathies, for which arrhythmias may be the first presentation. Ventricular and atrial arrhythmias presenting in the absence of known myocardial disease are often labelled as idiopathic, or lone. While ventricular arrhythmias are well-recognized as presentation for arrhythmogenic cardiomyopathy in the right ventricle, the scope of arrhythmogenic cardiomyopathy has broadened to include those with dominant left ventricular involvement, usually with a phenotype of dilated cardiomyopathy. In addition, careful evaluation for genetic cardiomyopathy is also warranted for patients presenting with frequent premature ventricular contractions, conduction system disease, and early onset atrial fibrillation, in which most detected genes are in the cardiomyopathy panels. Sudden death can occur early in the course of these genetic cardiomyopathies, for which risk is not adequately tracked by left ventricular ejection fraction. Only a few of the cardiomyopathy genotypes implicated in early sudden death are recognized in current indications for implantable cardioverter defibrillators which otherwise rely upon a left ventricular ejection fraction ≤0.35 in dilated cardiomyopathy. The genetic diagnoses impact other aspects of clinical management such as exercise prescription and pharmacological therapy of arrhythmias, and new therapies are coming into clinical investigation for specific genetic cardiomyopathies. The expansion of available genetic information and implications raises new challenges for genetic counseling, particularly with the family member who has no evidence of a cardiomyopathy phenotype and may face a potentially negative impact of a genetic diagnosis. Discussions of risk for both probands and relatives need to be tailored to their numeric literacy during shared decision-making. For patients presenting with arrhythmias or cardiomyopathy, extension of genetic testing and its implications will enable cascade screening, intervention to change the trajectory for specific genotype-phenotype profiles, and enable further development and evaluation of emerging targeted therapies.

Ventricular arrhythmia management in patients with genetic cardiomyopathies

Genetic cardiomyopathies are associated with increased risk for cardiac arrhythmias and sudden cardiac death. The management of ventricular arrhythmias (VAs) in patients with these conditions can be nuanced due to particular disease-based considerations, yet data specifically addressing management in these patients are limited. Here we describe the current evidence-based approach to the management of ventricular rhythm disorders in patients with genetic forms of cardiomyopathy, namely, hypertrophic cardiomyopathy, arrhythmogenic cardiomyopathy, left ventricular noncompaction, and Brugada syndrome, including recommendations from consensus guideline statements when available.

Non-invasive markers for sudden cardiac death risk stratification in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a common yet challenging cardiac disease. Great strides have been made in improving DCM prognosis due to heart failure but sudden cardiac death (SCD) due to ventricular arrhythmias remains significant and challenging to predict. High-risk patients can be effectively managed with implantable cardioverter defibrillators (ICDs) but because identification of what is high risk is very limited, many patients unnecessarily experience the morbidity associated with an ICD implant and many others are not identified and have preventable mortality. Current guidelines recommend use of left ventricular ejection fraction and New York Heart Association class as the main markers of risk stratification to identify patients who would be at higher risk of SCD. However, when analysing the data from the trials that these recommendations are based on, the number of patients in whom an ICD delivers appropriate therapy is modest. In order to improve the effectiveness of therapy with an ICD, the patients who are most likely to benefit need to be identified. This review article presents the evidence behind current guideline-directed SCD risk markers and then explores new potential imaging, electrophysiological and genetic risk markers for SCD in DCM.

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

Background - Truncating variants of the titin gene (TTNtv) are a leading cause of dilated cardiomyopathy (DCM) and have been associated with an increased risk of ventricular arrhythmias. This study evaluated the substrate distribution and the acute and long-term outcomes of patients with TTN-related cardiomyopathy undergoing ventricular tachycardia (VT) ablation. Methods - This multicenter registry included 15 patients with DCM (age 59±11 years, 93% male, ejection fraction 30±12%) and genotypically confirmed TTNtvs who underwent VT ablation between July 2014 and July 2020. Results - All patients presented with sustained monomorphic VT, including electrical storm in 4 of them. A median of 2 VTs per patient were induced during the procedure (cycle-length 318±68 ms) and the predominant morphologies were left bundle branch block with inferior axis (39%) and right bundle branch block with inferior axis (29%). A complete map of the left ventricle (LV) was created in 12 patients and showed voltage abnormalities mainly at the periaortic (92%) and basal septal region (58%). A preprocedural cardiac magnetic resonance imaging was available in 13 patients and in 11 there was evidence of LV delayed gadolinium enhancement, with predominantly midmyocardial distribution. Sequential ablation from both sides of the septum was required in 47% of patients to target septal intramural substrate and epicardial ablation was performed in 20%. At the end of the procedure, the clinical VT was noninducible in all patients, while in 3 cases a non-clinical VT was still inducible. After a follow-up of 26.5±23.0 months, 53% of patients experienced VT recurrence, 20% received transplant or mechanical circulatory support and 7% died. Conclusion - The arrhythmogenic substrate in TTN-related cardiomyopathy involves the basal septal and perivalvular regions. Long-term outcomes of catheter ablation are modest, with high recurrence rate, likely related to an intramural location of VT circuits.