The most important genes related with AF are KCNQ1 (encoding the alpha-subunit of IKs channel) [10], which is involved in type 1 Long QT Syndrome (LQTS) [11], and familial forms of AF, TTN (encoding titin), implicated in approximately 25% of familial dilated cardiomyopathies (DCM) [12] and Lamin A/C (LMNA), involved in 5–10% of DCMs and considered an arrhythmogenic gene related to arrhythmias (in particular, atrial ones), conduction diseases and sudden cardiac death (SCD) [13]. The gene discussed is TTN; the disease is familial long QT syndrome.