The displacement of an electrode and incorrect connection of the electrode to the generator are both documented causes of early complications in pacemaker implantation. These problems can cause a loss of capture and are usually detected during the postoperative period in the hospital. Patients undergo immediate revision.

Common causes of late pacemaker failure are the loss of battery power and a sudden increase in stimulation threshold, or both. These problems lead to loss of capture. Once the battery begins to fail, there is a decrease in the stimulation rate and a change in the fixed-rate mode. The spike may still be recorded on ECG, but it is not followed by a QRS complex.

Once the battery is depleted, the generator must be replaced immediately. Most pacemakers give an alert 1 month in advance and note the lifetime of the generator battery. The pacemaker must be maintained at all times, especially in pacemaker-dependent patients where a long ventricular pause may have significant hemodynamic effects.