Accompanying the clear benefits, there are certain risks of tachyarrhythmias in percutaneous coronary interventions (PCI), including serious ventricular arrhythmias and atrial fibrillation (AF). Ventricular arrhythmias may result from excess catheter manipulation, intracoronary dye injection, new ischemic events, or reperfusion. In patients with heart failure such kind of arrhythmias can occur more frequently. Atrial dysfunction, sino-atrial and nodal ischemia, congestive heart failure, sympathetic stimulation, iatrogenic factors are the possible causes of AF especially in patients undergoing primary PCI. Atrial fibrillation, on the other hand, can cause clinical squeal in the setting of a rapid ventricular response or if the loss of atrial systole results in hypotension, as in a patient with mitral stenosis or diastolic ventricular dysfunction. Majority of the ventricular arrhythmias and AF tend to revert spontaneously. However, the special treatment must be given, when necessary.