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What is a Demand Pacemaker?

By C. Stoliecki
Updated Feb 18, 2024
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Artificial pacemakers, also called pacemakers, discharge electrical impulses in two ways. They can be programmed to emit electrical impulses at a steady rate that does not respond to the activity of the heart. These are known as fixed-rate pacemakers. Alternatively, demand pacemakers can discharge electrical impulses when the heart rate falls outside of a predetermined zone or skips a beat. Demand pacemakers are thus used to regulate arrhythmias, which are heart rhythms that are irregular, where the heart beats either too rapidly or too slowly.

Pacemakers that work on demand are known as permanent pacemakers. They are implanted to regulate heart-rate problems that occur over extended periods of time. In 1958, Wilson Greatbatch and W.M. Chardack created the first implantable permanent pacemaker. Just six years later in 1964, Greatbatch designed the demand pacemaker, which became available for use in 1966. The advantages of using demand pacemakers were realized shortly after this.

One advantage of a demand pacemaker is that they prevent the occurrence of what are known as competitive beats. They occur when the heart’s intrinsic pace-making mechanism and an fixed-rate pacemaker stimulate a heartbeat at the same time. This simultaneous firing usually happens because arrhythmias are only intermittent. When they are not occurring, the heart’s intrinsic pacemaker fires and the heart beats normally. A fixed-rate pacemaker cannot detect intrinsic heartbeats and will emit electrical impulses at the same time that the hearts own pacemaker fires, causing the competitive beats. Once thought to be harmless, competitive beats have been associated with higher mortality rates and health problems in pacemaker patients.

The demand pacemaker senses the activity of the heart, which allows it to refrain from emitting electrical impulses while the heart is intrinsically firing. This eliminates the possibility for competitive beats to occur. Doing so has increased the clinical applicability of pacemaker treatment for conditions that would elicit a competitive beat from a fixed-rate pacemaker, but would benefit from some sort of pacing nonetheless.

Another advantage of the demand pacemaker is that firing less often allows it to reserve its battery power for a much longer period of time than fixed rate pacemakers. Demand pacemakers are also advantageous because they protect against a condition known as ventricular asystole. Ventricular asystole refers to the lack of mechanical and electrical activity in the heart—a condition that can cause a person to faint and is in many cases fatal. In sensing the absence of a heartbeat, the demand pacemaker sends an electrical impulse to catalyze the heart to prevent fainting or death from occurring.

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Discussion Comments
By KoiwiGal — On Oct 09, 2012

@pleonasm - There are still places in the world where that can happen, not everyone has access to modern medicine. But generally I think needing a pacemaker happens from people being too overweight all their lives, or smoking or whatever. So, there wouldn't have been as many calls for pacemakers back in the old days anyway.

By pleonasm — On Oct 08, 2012

@bythewell - I find it amazing how many people need pacemakers. It makes me sad to think that only a hundred years ago those people would have just eventually died. When my uncle had to have one put in, he was fairly young and they told us it was probably some kind of virus that damaged his heart so it wasn't working properly.

He would just get very tired every time he tried to go anyway or do anything and walking faster than a very slow pace was impossible without chest pain and trouble breathing. It got worse and worse before they finally gave him the pacemaker. I just can't imagine being in the old days and knowing what was wrong (because they knew the problem long before they could correct it) and not being able to do anything about it. Thank god for modern technology.

By bythewell — On Oct 07, 2012

My mother got a demand pacemaker put in at the beginning of the year and we were quite astonished at how advanced all the technology seems to be. I couldn't believe that pacemakers had been around since the 60's, which they still kind of seem like a space-age technology.

Now, my mother can go into a hospital and they can wave something in front of the pacemaker and it will tell them all the information about how her heart has been working, whether it needs to be adjusted and all.

She had a few problems with it at first but it got better with time and apparently the battery will last for about ten years, so she's not go to worry about it until then.

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