Common presentation of rare cardiac diseases: Arrhythmias.

Ventricular or supraventricular ectopic beats or atrial fibrillation may be the first presentation of uncommon cardiac disease, both acquired and genetically determined. In some patients, these manifestations can be the first sign of the underlying cardiac disorder. In others, however, they are also important as prognostic indicators, reflecting electrical instability and risk. Most cardiology clinics are busy environments where the implementation of complex diagnostic algorithms is not feasible. However, it is equally impossible to reach a final diagnosis, among the thousands of rare diseases that involve the heart, moving from a first line clinical and instrumental examination. Cardiac and extra-cardiac red flags, an accurate family and clinical history and ECG interpretation may be of help in identifying a rare disease. Advanced imaging and laboratory testing at experienced referral centers is then necessary to reach a final diagnosis, but the first step in the right direction, based on these simple elements, is the most important. We here review arrhythmic presentations of rare or relatively rare diseases, and suggest a simple "rule out-rule in" approach to help direct clinical suspicion and minimize risk of neglect.