The Natural History and Clinical Outcomes of Transmembrane Protein 43 Cardiomyopathy: A Systematic Review

Background: Arrhythmogenic cardiomyopathy (ACM) is an inherited heart disorder characterized by structural and functional myocardial alterations, often accompanied by ventricular arrhythmias (VAs), which may ultimately result in sudden cardiac death (SCD). While mutations in genes coding for desmosomal components are commonly identified in affected individuals, genetic variants involving non-desmosomal proteins have recently been recognized as contributors to the disease’s etiology. In 2008, a mutation in the transmembrane protein 43 (TMEM43) was identified as being responsible for a fully penetrant, sex-related, and severe form of ACM. This review aimed to systematically synthesize the current evidence on the natural history, electrocardiographic, and imaging findings as well as the clinical outcomes of TMEM43 cardiomyopathy. Methods: A systematic search was performed in the PubMed, Scopus, and Web of Science databases, following the PRISMA guidelines, using the terms “TMEM43” AND “cardiomyopathy”. After an initial screening of 144 retrieved articles, 80 were considered relevant. Upon a full-text review and eligibility assessment, 12 studies involving 903 individuals harboring TMEM43 variants were selected for inclusion. Results: Male patients more frequently carried the pathogenic TMEM43 variant (n = 505, 55.9%) and exhibited an earlier arrhythmic onset of the disease (33.2 years old versus 46.2 years old in female patients), supporting the need for earlier implantable cardioverter–defibrillator implantation (30.4 versus 42.2 years old). Palpitations, chest pain, and syncope were the most common presenting symptoms. Baseline electrocardiograms commonly demonstrated poor R wave progression, QRS prolongation, and premature ventricular contractions (PVCs). Arrhythmic events, including malignant VAs and SCD, were early manifestations of the disease, especially in male patients. Frequent PVCs and left ventricular dilation were considered early markers of the disease and were predictive of arrhythmic events. Conversely, heart failure was reported as a late clinical outcome, requiring heart transplantation in a minority of cases (1.5%). Conclusions: TMEM43 cardiomyopathy is a fully penetrant autosomal dominant form of ACM, characterized by a well-defined clinical phenotype that is more severe and presents earlier in male patients.