This thesis explores the importance of antiarrhythmic drugs in the treatment of arrhythmia with a focus on evidence-based clinical practice. Although a lot of new drugs have been added to a modernized classification of antiarrhythmic drugs, most of them are not used in clinical practice. This thesis concentrates more on antiarrhythmic drugs that are used in daily practice and provides more information on antiarrhythmic drugs from recent trials and guidelines of the European Society of Cardiology for arrhythmia. Furthermore, heart rate variability is also mentioned. Heart rate variability measures provide a good prognostic and allow physicians to provide appropriate treatment in patients with high risk after myocardial infarction. Heart rate variability is also helpful in early detection of diabetic autonomic neuropathy. Although some papers show some correlation between heart rate variability and antiarrhythmic drugs, more large-scale studies are needed before these associations can be used extensively in clinical practice.