Arrhythmia or altered heart rhythms can present with or without underlying heart disease. Most cardiopathies give rise to arrhythmias; however, arrhythmias can also be caused in previously healthy hearts by other conditions such as metabolic disorders, electrolyte imbalances, and drug use or abuse. The clinical presentation can range from asymptomatic cases discovered incidentally on routine examination to sudden death as the only clinical sign. In cases with clinical suspicion of arrhythmia, Holter and electrophysiological studies should be performed. If the condition is confirmed, associated cardiopathy must be ruled out. Echocardiography should be the first imaging test to be performed. Multidetector computed tomography (CT) and magnetic resonance imaging (MRI) have been applied to the field of cardiology more recently and are gradually acquiring specific roles with precise indications. In the study of arrhythmias, MRI is indicated in two particular areas: auricular fibrillation and arrhythmogenic right ventricular dysplasia.