The Electrophysiology Lab

Artificial Cardiac Pacemaker
Implantable Cardioverter Defibrillator
Ablation

Artificial Cardiac Pacemaker
Treatment with an artificial cardiac pacemaker has made great strides in becoming safer and applicable to a larger group of patients. An electrical device, the pacemaker, is surgically implanted to override or supplement the heart's own pacemaker and electrical conduction system. The treatment may be used for temporary assistance or for long-term therapy of abnormal heart rhythms.

The pacemaker weighs about 1 1/2 ounces and is powered by a lithium battery which can last up to 10 years. The pacemaker is placed beneath the skin just below the collarbone on the right side of the chest. One type is connected to an insulated wire lead that is passed through a large vein into the right side of the heart. Most often, this type of pacemaker is required in treatment of bradycardia (abnormally slow heartbeat). The pacemaker is programmed to sense when the heart's rate drops below a pre-set limit and to discharge an electrical impulse to the heart wall. These limits can be set and re-set by the physician after the pacemaker is implanted. A two-wire model may be used to correct sequence problems by making sure the atria contract before the ventricles in every cardiac cycle.

Pacemakers used today are very different from models used 10 and 20 years ago and most patients no longer have to worry about electrical interference from such appliances as microwave ovens. However, caution is still important when the patient may be exposed to high voltage transmission lines and substations, arc welding and magnetic resonance imaging technology. It is also important to protect the pacemaker and insertion site from injury due to a hard blow to the chest or sustained, extreme pressure against the chest.

Implantable Cardioverter Defibrillator
The implantable defibrillator is another device that is designed for electrical stimulation of the heart tissue. It is different from a pacemaker in that it is used to treat patients at risk of recurrent, sustained ventricular tachycardia (abnormally fast heartbeat) or fibrillation (ineffective "quivering" of the heart which can result in cardiac arrest). The defibrillation device is connected to leads positioned either inside the heart or on the heart surface. These leads sense the normal heart rhythm, detect abnormalities and deliver shocks to the heart as needed to return the heart to a normal rhythm. The internal device is connected to an implanted pulse generator at a separate site. Some models also can be used to supplement heart rate in the event of a slower than normal beat.

In years past, a relatively larger device was implanted during open chest surgery with electrode leads placed directly on the heart surface. The leads were then connected to a wallet-size generator placed under the skin in the abdomen. About half of all patients who could have benefitted from the treatment were considered poor risks for such major surgery. Today, a non-surgical approach has increased the number of patients who can be considered for implantation. This technique involves insertion of the electrode wires into the heart by passage through veins leading to the heart with an electrode patch placed just under the skin.

Ablation
Ablation is a treatment for abnormal heart rhythms that can be traced to specific tissues in the heart wall that are causing abnormalities in heart rhythm or impulse conduction. It involves destructing the defective tissue in the heart, through a surgical open-heart procedure or the new transcatheter tecgnique Saint Francis physicians have helped to develop. In the transcatheter procedure, a special low-level radio-frequency energy is used to produce ablation. A specially designed catheter destroys the tissue in less than half the time and with greater accuracy than previous techniques. Also, with the newer techniques, patients do not need general anesthesia. Three-dimensional EKG mapping, also developed by a Saint Francis heart specialist, has improved the precision of the ablation procedure which is rapidly becoming the technique of choice for many supraventricular tachycardias.