Pacemaker and Defibrillator Devices

The heart depends on electrical impulses to control its speed and rhythm.  When the heart’s electrical system is faulty, patients may develop an abnormal heart beat, or arrhythmia.  There are several different types of arrhythmias, including fast, slow and irregular heart beats.

Pacemakers

Some patients, particularly those over age 70, develop an abnormally slow heartbeat which may or may not be associated with other cardiac disease.  Patients with a heart rate of less than 50 beats per minute who are not on medicines that slow the heart rate should be considered for pacemaker implantation.

A pacemaker is a small device consisting of a battery and a computer chip.  The pacemaker is connected to one or more insulated wires that deliver a very tiny electrical impulse to the heart causing it to beat.  Placement of a pacemaker is usually a brief out-patient procedure where the device is inserted into a small “pocket” below the collarbone.  The insulated wires are placed into the heart using X-ray guidance.  Pacemakers have many features which are programmable, permitting the physician to tailor the settings to each patient’s needs.

Defibrillators

Some patients, usually those with a history of significant heart disease, have impaired heart function where the heart loses its ability to contract, or squeeze, normally.  The heart’s ability to squeeze is called its “ejection fraction.”  When the heart’s ejection fraction falls below 30 – 35%, a patient is at greater risk for sudden cardiac death.  Sudden cardiac death, if untreated, is a lethal cardiac rhythm disturbance which can be effectively treated with an implantable cardiac defibrillator.

An implantable cardiac defibrillator is larger than a pacemaker but similar in shape and design.  It consists of a larger, more powerful battery and a sophisticated miniature computer.  Placement of an implantable defibrillator is often an out-patient procedure where the device is inserted into a “pocket” below the collarbone.  A defibrillator is connected to one or more insulated wires, which are placed into the heart using X-ray guidance.  Defibrillators are programmed to sense all cardiac rhythm disturbances.  If a lethal rhythm disturbance is sensed, then the defibrillator delivers an internal shock to the heart.  Defibrillators also function as pacemakers. 

Bi-Ventricular Pacemakers and Defibrillators

Some patients with congestive heart failure will have an abnormality in the timing of the contraction of the heart’s pumping chambers.  When this occurs, the heart contraction is less effective and symptoms of heart failure worsen.  Pacemakers and defibrillators have been developed which permit pacing of both pumping chambers of the heart.  These bi-ventricular devices are very similar to pacemakers and defibrillators, with the addition of another insulated wire.  They are implanted into a “pocket” under the collarbone usually as an out-patient procedure.

Cardiac resynchronization therapy, using bi-ventricular pacemakers and defibrillators, can improve the heart’s coordination of contraction.  Patients may benefit with increased exercise tolerance, lessened severity of heart failure and improved quality of life.

Epicardial Left Ventricular Lead Placement

Occasionally the insulated pacing wire to the left ventricle of a bi-ventricular pacemaker or defibrillator is unable to be threaded into proper position within the vein overlying the left ventricle. Therefore,  a minimally invasive approach using scopes and extremely small port access sites may be used to attach the pacing wire to the surface of the left ventricle.  Cardiac resynchronization therapy can then be initiated.