Pacemaker

Pacemakers (PMs) are used to treat bradyarrhythmias. These devices lie in a subcutaneous “pocket” on the chest and has electrodes going into the heart. The device either continuously paces the heart or paces the heart when it detects that the heart rate is going below a certain threshold, depending on the settings.

The pacemaker can be put into a variety of different modes, each described by a three-letter code describing the function of that mode. The most important indications for pacemakers and the modes used are:

• Sick sinus syndrome (SSS) – AAI mode
• AV block – VDD or DDD mode
• Atrial fibrillation – VVI mode

Not all pacemakers are permanent; temporary pacemakers exist as well. These can pace the heart transcutaneously or transvenously. Temporary pacemakers may be used while the patient is waiting to get a permanent one implanted, or if there is a reversible cause of the pacemaker indication.