Internal pacingA pacemaker is an electronic treatment for dangerously slow heartbeats. Without treatment, a slow heartbeat can lead to weakness, confusion, dizziness, fainting, shortness of breath and death.

Slow heartbeats (Brachycardia) can be the result of metabolic abnormalities or occur as a result of blocked arteries to the heart's conduction system. These conditions can often be treated and a normal heartbeat will resume. Slow heartbeats can also be a side effect of certain medications in which case discontinuation of the medicine or a reduction in dose may correct the problem.

But sometimes, the conduction system of the heart becomes irreversibly damaged for any one of a number of reasons. And some people require medications that cause slow heartbeats as a side effect in order to prevent other serious problems. Since there is no medication that one can take on chronic basis to speed up the heart rate, a pacemaker is the only solution.

Paced rhythm with single failure to capture

Paced rhythm with single failure to capture

Fortunately, having a pacemaker implanted is only a minor surgical procedure. This is not open-heart surgery. After a pacemaker is implanted, most people resume their previous lifestyle with little or no limitations.

The procedure is performed with mild sedation and a local anaesthetic. Patients are not put to sleep. A 2-inch incision is made parallel to and just below a collarbone. Pacer wires are then inserted into a vein that lies just under the collarbone and advanced through that vein under (X ray) fluoroscopic guidance into the heart. The other end of the pacer wires are connected to a "generator" that is implanted under the skin beneath the collarbone. This generator is about half an inch deep and one and a half inches wide. The skin is then sutured closed and the patient leaves the hospital later that same day or the following day. Incisional pain is mild and transient. It is possible to feel the pacer generator under the skin and a slight deformaty of the skin can be visually noticed.

Patients may not shower for a week after the procedure to keep the incision dry and should avoid excessively exerting the arm on the side the pacer was placed for that week.

After a week, the patient may resume their prior lifestyle without limitation. Household appliances do not interfere with modern day pacemakers. However, mobile phones may. These should be kept 12 inches away from the pacemaker when on-preferably at the ear on the opposite side of the pacemaker. A mobile phone should never be left in a pocket overlying the pacemaker.

Pacemaker are programmed to suit the patients specific requirements using a pacemaker programmer. Patients with pacemakers should avoid powerful electromagnetic fields which may reprogram the pacemaker. MRI (magnetic resonance imaging) scans cannot be performed on patients with pacemakers for that reason.

Pacemaker programmerPacemaker programmer

The pacemaker generator contains a lithium battery and what is, essentially, a little computer. The generator can communicate with an external device (connected to a pacemaker programmer) which is placed on the skin overlying the pacemaker. Through this device, a physician can change the programming of the pacemaker to best suit the individual patient's needs and investigate the status of the pacemaker. Some pacemakers also report on the performance of the patient's heart.

Pacemakers can also be checked over the telephone. The patient places a device and a magnet over the pacemaker and the pacemaker transmits a signal over phone line that is analysed in the physicians office.

Pacemaker batteries give off warning signals when they are running low on power many months before they actually fail. This can be detected either by a telephone check or by a formal interrogation by the external device mentioned above. Pacemakers are generally checked at least every 3 months to allow plenty of time to change the generator when it is running low on power. Changing the generator simply means remaking the same incision, removing the old generator, and plugging the existing wires into the new generator. The patient goes home the same day. Most batteries last at least 5 years.

Pacemakers sense every heartbeat the patient has and only pace the heart when the patient's heart rate falls below a predetermined limit. Patients are usually completely unaware of when the pacer is pacing their heart. In some patients, the pacemaker only needs to fire very rarely because the slow heartbeat only occurs intermittently. In other patients, the heartbeat is always too slow and the pacemaker has to pace the heart all of the time. Such patients are said to be pacemaker dependent.

Another use of pacemakers is for a disease called hypertrophic obstructive cardiomyopathy. This is a disease where overgrown heart muscle blocks the egress of blood out of the heart. By altering the electrical activation pattern of the heart's muscle, pacemakers can help alleviate this problem.

There are two other investigational uses of pacemakers. To prevent abnormally fast heart rhythms from developing in the upper chambers of the heart (the atria), some researchers are experimenting with pacing the atria from two sites instead of just one. To improve the pumping ability of the lower chambers of the heart (the ventricles) when they have been damaged by some disease, researchers are experimenting with pacing those chambers from two different sites to improve the efficiency and co-ordination of their muscular contraction.




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