Central Arkansas Cardiology

Pacemakers & Defibrillators

PACEMAKERS AND DEFIBRILLATORS
If a patient suffers from a slow or a fast heartbeat, there are implantable devices that will make the heartbeat regular and treat an arrhythmia. Slow heartbeats are treated with pacemakers. Fast, dangerous heartbeats, which may lead to cardiac arrest, are treated with implantable cardioverter-defibrillators. PACEMAKERS In patients who experience fatigue, dizziness, or fainting with a slow heartbeat, a mechanical generator is necessary to pace the heart to allow normal blood flow. Pacemakers are small computers and are now very small - about the size of two half-dollars placed on top of one another. The generator, which gets placed under the skin, by the left or right collar bone, is attached to either one or two small wires that get placed into the vein and into the right side of the heart. Pacemakers are programmed by the physician and the batteries usually last 5-10 years.

A patient who needs a pacemaker will be admitted to the hospital. In the electrophysiology laboratory, under conscious sedation, the pacemaker generator gets placed under the skin. Veins that run underneath both sides of the collar bone are used to access entry to the right side of the heart. The wires are placed in these veins, called subclavian veins. The wires are then attached to the generator and the wound is closed. The incision is about 4 centimeters. The patient stays overnight in the hospital. After a pacemaker is placed, there are virtually no limitations for the patient, other than decreased movement of the arm on the side where the pacemaker was placed for 1-2 weeks. In this day and age, pacemakers are covered in titanium. This prevents abnormal function from environmental electrical signals. Patients with pacemakers can use household appliances, cellular telephones, and microwave ovens. Only large magnetic field is dangerous in a patient that has a pacemaker. A large magnetic field is only encountered by the patient in the setting of an MRI. CT scans, ultrasounds, and other medical imaging devices are still allowable after implantation of a pacemaker.

IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS
An implantable cardioverter-defibrillator is a device that resuscitates the heart - attempts to restore a normal heart beat in a patient whose heart is beating rapidly and in a disorganized way. This is a life-saving therapy and is similar to the machines ambulances bring to patients in the midst of cardiac arrest (no heart blood output). In patients with significant heart disease who are determined to be at risk of sudden cardiac death, implantable cardioverter-defibrillators are placed to shock the heart and resuscitate the patient. An implantable cardioverter-defibrillator is about the size of a Zippo lighter. It gets hooked up to a wire placed in the right side of the heart much like a pacemaker. An implantable cardioverter-defibrillator has the capacity to pace the heart like a pacemaker, but it also has the capability to shock the heart and resuscitate or abort a cardiac arrest. The procedure is performed at Baptist Hospital or St. Vincent Infirmary. Under light sedation, a 5-centimeter incision is made either on the left or the right chest, just below the clavicle. The battery is placed under the skin and a vein located underneath the left or the right clavicle is isolated the wires are placed through that vein to allow entry to the right side of the heart. The wires are attached to the device and the wound is closed. When the patient undergoes implantation of an implantable cardioverter-defibrillator, they also will need testing of the device. Testing of the device requires sedation while the physician puts the patient into their arrhythmia. Under monitored conditions, the device treats the arrhythmia and places the patient back into their normal rhythm. An overnight stay in the hospital is expected for this type of procedure.

OFFICE FOLLOW-UP
Follow-up of both implantable cardioverter-defibrillators and pacemakers require office visits. Using computer programmers, the devices can be manipulated, interrogated, and programmed through the skin. The followup of all these devices is noninvasive and no further surgery is required unless the battery needs to be replaced in its due time. As with pacemakers, the strong magnetic fields in a Magnetic Resonance Imaging Unit is dangerous to implantable cardioverter-defibrillators. Microwave ovens, cellular telephones, and most household appliances are acceptable. Because a patient with an implantable cardioverter-defibrillator is at risk for cardiac arrest, patients can expect to not be allowed to drive for up to two months after implantation of the device. As technology evolves, both pacemakers and implantable cardioverter-defibrillators become more "intelligent" and smaller. The technology allows better monitoring of the heart and storing of any cardiac events. This information can be accessed by any physician at any time.

Whether a patient needs a pacemaker or an implantable cardioverter-defibrillator, is a complicated decision dependent on a patient's history, an electrophysiology study, and other cardiac therapy.

Exercise and Rest Myocardial Perfusion Imaging (also called a MIBI, Cardiolyte, Myoview, or Thallium stress tests): The noninvasive assessment of coronary artery disease via treadmill stress testing which can detect blockages significant enough to prevent adequate blood flow to the heart during exercise. These tests also definitively examine any damage done to the heart from prior heart attacks and can determine viability of heart muscle which may return to normal function if appropriately revascularized (i.e. with angioplasty or bypass surgery.) They also provide a highly accurate assessment of the contracting performance of your heart - both regional wall motion and ejection fraction of the left ventricle.
Pharmacologic Stress Myocardial Perfusion Imaging (Adenosine stress test) Uses medications which simulate the physiologic effect of exercise (instead of exercise) in those who are unable to perform on a treadmill test. The same assessment of coronary blood flow and left ventricular function may then be performed as in the exercise perfusion imaging.
Radionuclide Ventriculography (also called a RNV or MUGA test): The noninvasive ability to evaluate the contraction pattern of your heart. We can determine the left ventricular global and regional function including calculation of left ventricular ejection fraction, assessment of regional wall motion, aneurysms and pseudoaneurysms.