Because the great majority of clinically relevant arrhythmias are based on the principle of reentry, the understanding of the basic principle of this mechanism leads to alternative nonpharmacological therapy for such arrhythmias. The reentry circuit might be interrupted definitively by surgical or catheter ablative procedures, such as DC-energy shock delivery or radiofrequency coagulation, which will both lead to complete prevention of the tachycardia. On the other hand, electrical stimulation may influence the circus movement by wavefront collision and thus interrupt the tachycardia after it started. Antitachycardia pacemakers work on this principle. One major impact of antiarrhythmic treatment is the prevention of sudden death. The implantable defibrillator is currently the only treatment that really proves to be reliable in aborting sudden death. It is therefore the "gold standard" of antiarrhythmic treatment in life-threatening arrhythmias.