Arrhythmogenic cardiomyopathy (ACM) is a group of arrhythmogenic disorders of the myocardium that are not caused by ischemic, hypertensive, or valvular heart disease. The clinical manifestations of ACMs may overlap those of dilated cardiomyopathy, complicating the differential diagnosis. In several ACMs, ventricular tachycardia (VT) has been observed at an early stage, regardless of the severity of the disease. Therefore, preventing recurrences of VT can be a clinical challenge. There is a wide range of efficacy and side effects associated with the use of antiarrhythmic drugs (AADs) in the treatment of VT. In addition to AADs, patients with ACM and ventricular tachyarrhythmias may benefit from catheter ablation, especially if they are drug-refractory. The differences in pathogenesis between the various types of ACMs can lead to heterogeneous distributions of arrhythmogenic substrates, non-uniform ablation strategies, and distinct ablation outcomes. Ablation has been documented to be effective in eliminating ventricular tachyarrhythmias in arrhythmogenic right ventricular dysplasia (ARVC), sarcoidosis, Chagas cardiomyopathy, and Brugada syndrome (BrS). As an entity that is rare in nature, ablation for ventricular tachycardia in certain forms of ACM may only be reported through case reports, such as amyloidosis and left ventricular noncompaction. Several types of ACMs, including ARVC, sarcoidosis, Chagas cardiomyopathy, BrS, and left ventricular noncompaction, may exhibit diseased substrates within or adjacent to the epicardium that may be accountable for ventricular arrhythmogenesis. As a result, combining endocardial and epicardial ablation is of clinical importance for successful ablation. The purpose of this article is to provide a comprehensive overview of the substrate characteristics, ablation strategies, and ablation outcomes of various types of ACMs using endocardial and epicardial approaches.

Saw-tooth cardiomyopathy (STC), a rare form of left ventricular cardiomyopathy characterized by saw-tooth like myocardial projections extending from the lateral walls towards the ventricular cavity, is a newly discovered cardiomyopathy first described in 2009. Detailed cardiac magnetic resonance can demonstrate multiple dense myocardial protrusions originating from the inferior wall, interventricular septum and lateral ventricular walls, which differ from typical left ventricular noncompaction. STC case reports are increasing since the first discovery. A total of ten cases have been reported. This review focuses on the clinical presentation and imaging features of this disease and analyzes the latest evidence regarding STC. Furthermore, we summarize the clinical evidence from the current decade, which may enhance detection and diagnosis of this disease in the future.

A genetic diagnosis of primary cardiomyopathies can be a long-unmet need in patients with complex phenotypes. We investigated a three-generation family with cardiomyopathy and various extracardiac abnormalities that had long sought a precise diagnosis. The 41-year-old proband had hypertrophic cardiomyopathy (HCM), left ventricular noncompaction, myocardial fibrosis, arrhythmias, and a short stature. His sister showed HCM, myocardial hypertrabeculation and fibrosis, sensorineural deafness, and congenital genitourinary malformations. Their father had left ventricular hypertrophy (LVH). The proband\'s eldest daughter demonstrated developmental delay and seizures. We performed a clinical examination and whole-exome sequencing for all available family members. All patients with HCM/LVH shared a c.4411-2A>C variant in ALPK3, a recently known HCM-causative gene. Functional studies confirmed that this variant alters ALPK3 canonical splicing. Due to extracardiac symptoms in the female patients, we continued the search and found two additional single-gene disorders. The proband\'s sister had a p.Trp329Gly missense in GATA3, linked to hypoparathyroidism, sensorineural deafness, and renal dysplasia; his daughter had a p.Ser251del in WDR45, associated with beta-propeller protein-associated neurodegeneration. This unique case of three monogenic disorders in one family shows how a comprehensive approach with thorough phenotyping and extensive genetic testing of all symptomatic individuals provides precise diagnoses and appropriate follow-up, embodying the concept of personalized medicine. We also present the first example of a splicing functional study for ALPK3 and describe the genotype-phenotype correlations in cardiomyopathy.

A neonate born of third-degree consanguineous marriage presented on day 12 of life with congestive cardiac failure. A male sibling died at 3 months of age, cause of which was not known. He was treated with decongestive measures and multiple inotropes. 2D Echocardiogram revealed severe Left ventricular dysfunction with prominent trabeculations and deep recesses in the left ventricle suggestive of Left ventricular non-compaction. He was also found to have horse-shoe kidney. Considering the presence of cardiac left ventricular non compaction, horse-shoe kidney and family history of neonatal death and pregnancy loss clinical exome sequencing was done. It detected a homozygous missense variant in exon 6 of the AGK gene suggestive of Senger\'s syndrome. Baby was on regular follow-up and was thriving well on diuretics, sacubitril-valsartan and weekly levosimendan infusions. At 8 months of age, cardiac transplantation was successfully done and baby has been doing well post-transplantation. LVNC in children is rare with an estimated incidence of 0.11 per 100,000, the highest incidence being during infancy. Senger\'s syndrome is autosomal recessive in inheritance. Senger\'s syndrome associated with Left ventricular non compaction has been reported only once in literature so far. Renal manifestations in the form of horse shoe kidney like in our index baby has not been reported previously with Senger\'s syndrome.

Ebstein\'s anomaly is a congenital malformation of the tricuspid valve characterized by abnormal attachment of the valve leaflets, resulting in varying degrees of valve dysfunction. The anatomic hallmarks of this entity are the downward displacement of the attachment of the septal and posterior leaflets of the tricuspid valve. Additional intracardiac malformations are common. From an embryological point of view, the cavity of the future right atrium does not have a direct orifice connected to the developing right ventricle. This chapter provides an overview of current insight into how this connection is formed and how malformations of the tricuspid valve arise from dysregulation of molecular and morphological events involved in this process. Furthermore, mouse models that show features of Ebstein\'s anomaly and the naturally occurring model of canine tricuspid valve malformation are described and compared to the human model. Although Ebstein\'s anomaly remains one of the least understood cardiac malformations to date, the studies summarized here provide, in aggregate, evidence for monogenic and oligogenic factors driving pathogenesis.

Cardiac development is a fine-tuned process governed by complex transcriptional networks, in which transcription factors (TFs) interact with other regulatory layers. In this chapter, we introduce the core cardiac TFs including Gata, Hand, Nkx2, Mef2, Srf, and Tbx. These factors regulate each other\'s expression and can also act in a combinatorial manner on their downstream targets. Their disruption leads to various cardiac phenotypes in mice, and mutations in humans have been associated with congenital heart defects. In the second part of the chapter, we discuss different levels of regulation including cis-regulatory elements, chromatin structure, and microRNAs, which can interact with transcription factors, modulate their function, or are downstream targets. Finally, examples of disturbances of the cardiac regulatory network leading to congenital heart diseases in human are provided.

Left ventricular noncompaction (LVNC) is commonly described as a congenital cardiomyopathy characterized by prominent myocardial trabeculae and deep intertrabecular recesses extending in the left ventricular chamber. Clinical presentation can differ considerably from asymptomatic individuals to those presenting with heart failure and other serious complications. Diagnosis is usually made by two-dimensional transthoracic echocardiography or cardiac magnetic resonance. Moreover, even if strain parameters are significantly reduced in patients with LVNC, they are not routinely investigated. Here, we report the case of a previously symptomless patient admitted to the hospital for pulmonary edema. Two-dimensional transthoracic echocardiography showed severe valvular heart disease and left ventricle pronounced trabeculation and remodeling, although speckle tracking echocardiography (STE) demonstrated only mild strain reduction. We, therefore, explore the possibility that STE may be useful to differentiate LVNC cardiomyopathy from LVNC phenotype due to severe remodeling.

Overlapping of left ventricular noncompaction (LVNC) and hypertrophic cardiomyopathy in the same patient is rare and is associated with a more severe clinical course and unfavorable prognosis. The present report describes the case of a severely regurgitant bicuspid aortic valve in a 68-year-old man with overlapping LVNC and asymmetrical septal hypertrophy. Aortic valve replacement controlled the left ventricular dilatation that occurred secondary to the volume overload induced by the valvular disease. However, even 3 years postoperatively, severe systolic dysfunction persisted due to the preexisting myocardial disease, requiring close and lifelong follow-up with special attention to life-threatening arrhythmias and thromboembolism.

Left ventricular noncompaction cardiomyopathy (LVNC) is a structural heart defect that has been associated with generation of arrhythmias in the population and is a cause of sudden cardiac death with severe systolic dysfunction and fatal arrhythmias. LVNC has gained increasing acknowledgment with increased prevalence. We conducted a systematic review of reported electrocardiogram (ECG) results for pediatric LVNC patients. EMBASE database query was performed, yielding 4531 articles related to LVNC between 1990 and December 2023. Patient age ranged from prenatal to 18 years of age. Qualitative analyses were performed to characterize individual arrhythmias, and summative interpretation of ECG evaluations was gathered for the entire cohort. Systematic review of 57 LVNC cases and ECG presentation revealed many waveform consistencies, including abnormal left ventricular, atrioventricular node, and interventricular septal patterns, and specifically a high incidence of Mobitz type II and Wolff-Parkinson-White waveforms. This review of ECG analysis reinforces the clinical and etiologic significance of pediatric LVNC. While LVNC in pediatric populations may not always present as acute clinical cases, further investigation into the electrophysiology of the disease supports the need for further evaluation and risk stratification for patients with suspected LVNC and/or ventricular arrhythmia.

Left ventricular noncompaction (LVNC) is a rare genetic and congenital disorder characterized by the excessive formation of blood-filled trabeculae and intertrabecular recesses in the uncompressed inner endocardial wall associated with a thin, compact wall, the mesocardium. Although LVNC was described for the first time as long ago as 1984, our understanding of the disease with regard to its genetic pattern, diagnosis, clinical presentation, and treatment is still scanty. LVNC can be present as an isolated condition or associated with congenital heart disease, genetic syndromes, or neuromuscular disease. This suggests that LVNC is not a distinct form of cardiomyopathy, but rather a morphological expression of different diseases. Recognition of the disease is of fundamental importance because its clinical manifestations are variable, ranging from the absence of any symptom to congestive heart failure, lethal arrhythmias, and thromboembolic events. The main cardiac symptoms associated with LVNC are related to HF, occurring in up to half of the patients. Atrial fibrillation can affect 25 % of adult patients and ventricular tachyarrhythmias up to around 50 %. There is a possible association between bradycardia and Wolff-Parkinson-White syndrome in pediatric patients with LVNC. Other frequent manifestations are related to thromboembolic events, such as stroke, pulmonary embolism, and mesenteric ischemia. In asymptomatic patients, LVNC is identified by echocardiography or when the patient is subjected to family screening. However, when the disease is identified during the fetal period, the presence of systemic diseases, such as mitochondrial alterations and metabolic disorders, is frequently reported.