Clinical classification of rare cardiac arrhythmogenic and conduction disorders, and rare arrhythmias

Rare cardiovascular diseases and disorders (RCDDs) constitute an important clinical problem, and their proper classification is crucial for expanding knowledge in the field of RCDDs. The aim of this paper is to provide an updated classification of rare arrhythmogenic and conduction disorders, and rare arrhythmias (RACDRAs). We performed a search for RACDRAs using the Orphanet inventory of rare diseases, which includes diseases with a prevalence of no more than 5 per 10 000 in the general population. We supplemented this with a search of PubMed and Scopus databases according to a wider definition proposed by the European Parliament and the Council of the European Union. RACDRAs are categorized into 2 groups, primary electrical disorders of the heart and arrhythmias in specific clinical settings. The first group is further divided into subgroups of major clinical presentation: disorders predisposing to supraventricular tachyarrhythmias, ventricular tachyarrhythmias, bradyarrhythmias, and others. The second group includes iatrogenic arrhythmias or heart rhythm disturbances related to medical treatment, arrhythmias associated with metabolic disorders, and others. We provide a classification of RACDRAs and supplement them with respective RCDDs codes. The clinical classification of RACDRAs may form a basis to facilitate research and progress in clinical practice, both in diagnostic and therapeutic approaches.