Pacemaker is a part of heart's electrical system. It replaces impaired chronotropic function by generating impulses. Heart's electrical system is consisted of pulse generator and electrodes which are attached to the surface of the myocardium. By generating a pulse, wave of depolarization spreads and causes contraction of the myocardium ensuring the normal rhythm of the heart. Indications for permanent pacemaker implantation in the past 20 years have greatly expanded and thus affected the number of implanted devices and the quality of life in cardiac patients. At the center of implantable pacemakers of The University Hospital Sisters of Charity in 2013., 242 devices were implanted. The most common indications are atrioventricular block, atrial fibrillation with ventricular bradyarrhythmias, sinus node dysfunction, carotid sinus hypersensitivity and infranodal conduction block. Depending on the disorder of the heart's electrical system, various types of pacemakers are installed. The most common pacemaker implanted at The University Hospital Sisters of Mercy is DDD pacemaker, dual-chambered device that has two electrodes, one in the right atrium, another in the right ventricle, and it allows "physiological" sequential stimulation of the heart.