Multiple forms of heart arrhythmias exist including atrial fibrillation, atrial tachycardia, supraventricular tachycardia (SVT) and ventricular tachycardia. This conditions may often be diagnosed with an ECG (electrical reading of the heart), 24 hour ECG (Holter monitor) or event recorder. Echocardiography and cardiac CT can sometimes help to diagnose the underlying cause of any arrhythmia. Cardiac MRI is an important tool in assessing the cause of cardiac arrhythmias and heart block. Cardiac MRI is also important for planning ablation procedures (localised burning of the focus of the arrhythmia).