TTR and cardiac arrhythmia: Clinical course of TTR-CA is characterized by two different stages (Figure 1): a pre-symptomatic stage, when fibrils progressively infiltrate the heart, causing initial and subclinical structural and functional alterations; in this stage, patients are usually asymptomatic and often elude the diagnosis; in a subsequent time, the symptomatic stage, the disease clinically manifests: patients suffer from progressive heart failure (HF), arrhythmias and conduction system disease, undergo clinical evaluation and are eventually diagnosed.