For long-term dual-chamber permanent pacing, atrial and ventricular lead stability is essential. In our overall experience with such pacing systems, four patients suffered cardiac arrest at a time distant from their pacemaker implantation. Since all four patients received prolonged closed chest cardiopulmonary resuscitation, we analyzed these events to determine whether dual-chamber endocardial electrodes would remain stable in such traumatic conditions. Reliable atrial and ventricular lead position was confirmed at autopsy in the three patients whose resuscitation attempts were unsuccessful and, in the fourth patient, by continued normal lead position and pacing function post-resuscitation. The keys to this stability include the use of tined atrial and ventricular endocardial leads and specific maneuvers at the time of implantation to verify fixation. Long-term stability of presently available endocardial leads in dual-chamber pacing systems can thus be anticipated.