The normal heart generally runs from 60 to 100 beats per minute. Some patients may have abnormalities which predispose to slow heart beats. This can present with lightheaded spells, passing out spells (syncope), or fatigue, inability to exercise.
Pacemakers are small devices which are used treat slow heart rhythms, consisting of a generator which contains the battery and computer mechanism, and leads which are wires which connect the generator to the heart. The generator is about the size of a half dollar coin, and sends a small electrical stimulus to the heart. It is implanted under the skin in the chest by the shoulder. The leads are thin, about the size of spaghetti, and are threaded through a vein into the heart. Depending on the type of rhythm problem the pacemaker may have one, two, or three wires.
Devices with one or two wires are used to treat slow heart rhythms with those with three wires used both for slow rhythms and also to treat certain patients with weak hearts to strengthen the pumping function.
The implantation procedure generally takes one hour, under local anesthesia with sedation, and is done by a cardiologist or a surgeon, often with an anesthesiologist, in an xray room in the catheterization lab or in the operating room. Patients may go home the same day or the following day.
The pacemaker is set during the implantation procedure, but can be reprogrammed in the cardiologist’s office to change the heart rate settings as needed. It is generally followed every three months either in the doctor’s office or through a device which connects by phone from home. The battery life depends on how often it is used to stimulate (pace) the heart , and usually last from six to 10 years. When the battery is low a new device is placed. The wires generally last indefinitely.
Patients can do all normal activity with a pacemaker including sports, travel, work. Patients generally do not feel the heart being paced. Most medical procedures and medications and activities can be done with pacemakers, with the exception of an MRI’s which only a limited number of pacemakers are compatible with.
Abnormal heart rhythms such as ventricular tachycardia and ventricular fibrillation are dangerous, potentially life threatening rhythms which can cause dizzy spells, passing out (syncope), or sudden death. Patients with these rhythms generally have predisposing factors such as scarring of the heart due to prior heart attack, weakening of the heart due to cardiomyopathy, or less commonly genetic predisposing factors such as long QT, Brugada’s and hypertrophic cardiomyopathy.
An implantable defibrillator consists of a generator similar to a pacemaker, although slightly larger, which contains a battery and computer mechanism which monitors the heart rhythm, can pace the heart if it is too slow, and can deliver a shock to the heart in the event of one of these life threatening arrhythmias. The generator connects to the heart with specialized wires, similar again to pacemaker wires but containing coils which are used to shock the heart. Defibrillators can have one lead, two leads, or as in pacemakers three leads which are then also used to strengthen a weak heart. The implant is placed under the skin, in the chest by the shoulder, similar to a pacemaker.
An ICD device is indicated in patients with predisposing factors such as a weak heart as primary prevention, meaning that it is used in those at risk even if they have not had one of these irregular rhythms. It is also indicated as secondary treatment in those who have had or been resuscitated from one of these arrhythmias, such as being shocked out of ventricular tachycardia or having a fainting spell. Multiple large studies have done showing significant survival benefit in ICD patients compared with those without them in appropriately selected patients.
Implantation of a defibrillator is similar to that of a pacemaker, the procedure being done with local anesthesia , sedation, and under x-ray and monitoring. In some procedures patients are given more anesthesia so that they are asleep and the device is tested by stimulating the heart into the ventricular arrhythmia and the device then shocks the heart back to the normal rhythm.
Patients with defibrillators can commonly do all activity, with most limitations being due to underlying disease. Driving is a common question in patients with defibrillators and is quite individual. MRI’s are not allowed in patients with ICD’s. The device is followed either in the physician’s office or over phone lines from home by specialized equipment. It can be reprogrammed and interrogated to give a very good history in the physician’s office. Lifespan of the battery is generally shorter than pacemakers with most devices lasting four to seven years until the generator needs to be changed. The leads are generally god indefinitely, although due to the increased complexity of ICD leads there is a slightly higher chance that a new lead is needed than in pacemakers.
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