Types of pacemaker

• pacemaker output generally stimulates the cavity of the right atrium and/or right ventricle (endocardial pacing). Sometimes leads are fixed to the external surface of the heart (epicardial pacing)
• the delivery system of the pacemaker is either unipolar (where a single contact is made with the heart) or bipolar. The pulse generator is internal in permanent pacemakers and external in temporary pacing

Bipolar (dual chamber) versus unipolar (single chamber) pacing (1):

• in elderly patients with high-grade atrioventricular block, the pacing mode does not influence the rate of death from all causes during the first five years or the incidence of cardiovascular events during the first three years after implantation of a pacemaker

Reference:

1. Toff WD et al. Single-chamber versus dual-chamber pacing for high-grade atrioventricular block. NEJM 2005; 353:145-55.