Artificial heart pacemaker
A pacemaker (or "artificial pacemaker", so as not to be confused with the heart's natural pacemaker) is a medical device designed to regulate the beating of the heart. The purpose of an artificial pacemaker is to stimulate the heart when either the heart's native pacemaker is not fast enough or if there are blocks in the heart's electrical conduction system preventing the
propagation of electrical impulses from the native pacemaker to the lower chambers of the heart, known as the ventricles. Generally, pacemakers do not treat fast rhythms of the heart.
When the lead from a single-chamber pacemaker is placed in the ventricle, the pacemaker is able to receive signals from and pace only the ventricle. If the lead is placed in the atrium, the pacemaker will be able to receive signals from and pace only the atrium. Depending on the cause and the nature of the bradycardia, the doctor decides where to place the single lead.
Dual chamber pacemakers have two leads: one in the atrium and one in the ventricle. Dual-chamber pacemakers are more complex and sophisticated than single-chamber pacemakers. A dual chamber pacemaker can receive signal from and pace both the ventricle and the atrium. It can also coordinate the signals and contractions of the atria and the ventricles to help the heart beat more efficiently.
In a normal contraction cycle in a normal heart, the atria contract first to deliver blood into the ventricles. The ventricles then contract after a short time interval. Dual-chamber pacemakers can coordinate the electrical signals to the atrium and the ventricle so that this natural sequence of contractions is followed. Following the natural sequence of contractions improves the pumping efficiency of the heart.
Dual-chamber pacemakers are more susceptible to problems because of their greater degree of sophistication. These pacemakers can cause the heart to race inappropriately if confused by the heart's own electrical activity. Also, additional leads mean that more equipment can potentially fail. Thus, not all patients are good candidates for dual-chamber pacemakers. Some patients are better served with a single-chamber pacemaker. A qualified cardiologist or electrophysiologist is ideal to decide which pacemaker is most appropriate.
External pacemakers can be used for initial stabilization of a patient, but implantation of a permanent internal pacemaker is usually required for most conditions. External cardiac pacing is typically performed by placing two pacing pads on the chest wall. Usually one pad is placed on the upper portion of the sternum, while the other is placed along the left axilla, near the bottom of the rib cage. When an electrical impulse goes from one pad to the other, it will travel through the tissues between them and stimulate the muscles between them, including the cardiac muscle and the muscles of the chest wall. Electrically stimulating any muscle, including the heart muscle, will make it contract. The stimulation of the muscles of the chest wall will frequently make those muscles twitch at the same rate as the pacemaker is set.
Pacing the heart via external pacing pads should not be relied upon for an extended period of time. If the person is conscious, he or she may feel discomfort due to the frequent stimulation of the muscles of the chest wall. Also, stimulation of the chest wall muscles does not necessarily mean that the heart is being stimulated as well.
An alternative to external pacing is the temporary internal pacing wire. This is a wire that is placed under sterile conditions via a central line. The distal tip of the wire is placed into either the right atrium or right ventricle. The proximal tip of the wire is attached to the pacemaker generator, outside of the body. Temporary internal pacing is often used as a bridge to permanent pacemaker placement. Under certain conditions, a person may require temporary pacing but would not require permanent pacing. In this case, a temporary pacing wire may be the optimal treatment option.
Placement of a permanent pacemaker involves placement of one or more pacing wires within the chambers of the heart. One end of each wire is attached to the muscle of the heart. The other end is screwed into the pacemaker generator. The pacemaker generator is a hermetically sealed device containing a power source and the computer logic for the pacemaker. Most commonly, the generator is placed below the subcutaneous fat of the chest wall, above the muscles and bones of the chest. However, the placement may vary on a case by case basis.
Most patients can eventually return to normal activities after receiving a pacemaker. In fact, patients with a pacemaker usually feel better and may be able to do more than before. It is normal to have some pain in the area around the implanted pacemaker for a week or so after the procedure. Patients are given pain medications to alleviate this post-surgical pain. It is also normal to feel some numbness and heaviness around the pacemaker for some months.
Patients can return to most of their normal daily activities a few days after the procedure. During the first weeks after the procedure, the patient is asked not to lift the arm on the side of the pacemaker implantation over the head. This precaution is to avoid dislodging the lead(s) and to allow the lead(s) to become firmly secured inside the heart. The patient is also asked to avoid heavy lifting, contact sports, and other vigorous exercises for a few weeks.
The sutures at the incision site are removed between one to two weeks after the procedure, usually in the doctor's office or in a pacemaker clinic. This is also the time to discuss with the doctor issues regarding activity levels, exercises, symptoms, when and how frequently to check the function and the battery levels of the pacemakers, signs of pacemaker malfunction, and precautions regarding interference from electrical appliances and devices.
Most doctors allow their patients to return to work in one to two weeks, even though the incision may take several weeks to heal completely. Some doctors recommend that their patients subscribe to telephone monitoring services. The pacemaker signals which are transmitted to the doctor' office or the pacemaker clinic by telephone can be analyzed to make sure the pacemaker is functioning properly.