A rare case of "runaway" pacemaker in a modern CPU-controlled pacemaker.

"Runaway" pacemaker is a rare entity that occurs when a malfunctioning artificial cardiac pacemaker abruptly accelerates its pacing rate above the set upper rate limit. This can result in life-threatening dysrhythmia. Runaway pacemaker used to occur more frequently in older model pacemakers, but now with newer pacemaker generators, runaway pacemaker is a rare entity. We report the case of a runaway pacemaker in a modern CPU-controlled pacemaker in a 79-year-old man presenting with lightheadedness and review the literature regarding this rare entity.