How does a pacemaker work?

The Pacemaker

A pacemaker is an electronic device used to prevent a heart from beating abnormally. It's a generator made up of a battery and computer circuitry housed in a metal casing. The casing is implanted under the skin in the upper chest or shoulder region. Pacemaker wires are threaded through the veins of the shoulder and guided into the heart with the help of X-rays. Once the wires are positioned in the heart they are hooked up to the generator.

The first permanent pacemaker implant happened in 1958. Today there are three basic types of pacemakers:

  • Single-chamber pacemakers, which carry electrical pulses from the generator to the right ventricle of the heart.
  • Dual-chamber pacemakers, which carry electrical pulses from the generator to both the right ventricle and right atrium of the heart. Dual-chamber devices coordinate the timing of the right ventricle and right atrium contractions.
  • Biventricular pacemakers add a third piece to the system. These devices, called cardiac resynchronization therapy (CRT), deliver electrical pulses from the generator to the right atrium, right ventricle and to the left ventricle as well.

There are two main types of pacemaker programming: demand and rate-responsive. A demand pacemaker is designed to sense when the heart needs assistance by measuring each heartbeat and firing when the heartbeat becomes too slow or misses a beat. Rate-responsive pacemakers adjust heart rates depending on the patient's level of activity. They measure the SA node rate but also breathing, blood temperature and other factors.

Today's permanent pacemakers last at least 6 to 10 years depending on how frequently the device has to work. Every time a pacemaker is triggered it drains its battery. Occasionally a temporary pacemaker is used, usually during a patient's recovery from a heart attack or during an emergency situation to immediately speed up a slow heart rate. Temporary pacemakers are similar to permanent types except they aren't usually implanted in the body.

Did You Know?

In September 2009 the Bharat Book Bureau reported that the global market value for pacemakers was $4.2 billion in 2008 and is expected to grow to $6.1 billion by 2015 due to a combination of increasing incidence of cardiovascular disease and a growing elderly population.

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