Hospital Services

Cardiac Electrophysiology Procedures
(Diagnose and/or Treatment of Heart Rhythm Disorders)

Implantable Cardioverter Defibrillators (ICDs)

Almost everyone has seen a physician on television, paddles in hand, yelling "Clear!", then applying those paddles to the chest of a patient to shock him "back to life". As dramatic as the scene may be, defibrillation, or shock, can be the only way to stop certain deadly heart arrhythmias before they kill.

For those who are at high risk of the deadliest forms of arrhythmias - ventricular tachycardia and ventricular fibrillation - an internal "shocking" device may provide the best defense against sudden cardiac arrest. Such a device, known as an implantable cardioverter defibrillator (ICD), is considered effective in fighting cardiac arrest over 90 percent of the time, an astounding success for a condition that few survived as recently as 15 years ago.

About ICDs

• Implantable cardioverter defibrillators (ICDs) are small devices, about the size of a pager, that are placed below the collarbone. Via wires, or leads, these devices continuously monitor the heart's rhythm. If the heart beats too quickly, the ventricles will not have enough time to fill with blood and will not effectively pump blood to the rest of the body. Left unchecked, the rapid heartbeat could cause death. To intervene, the ICD issues a lifesaving jolt of electricity to restore the heart's normal rhythm and prevent sudden cardiac death.
• ICDs also can act as pacemakers when a heartbeat that is too slow (bradycardia) is detected.
• Most ICDs keep a record of the heart's activity when an abnormal heart rhythm occurs. With this information, the electrophysiologist, a specialist in arrhythmias, can study the heart's activity and ask about other symptoms that may have occurred. Sometimes the ICD can be programmed to "pace" the heart to restore its natural rhythm and avoid the need for a shock from the ICD. Pacing signals from the ICD are not felt by the patient; shock signals are, and have been described as a kick in the chest.

Sudden Cardiac Death Vs. Heart Attack:

• Cardiac arrest, or sudden cardiac death (SCD), happens when a heart rhythm disturbance prevents the heart from operating properly and delivering blood to the brain and other vital organs.
• A heart attack occurs when a partial or complete vessel blockage interferes with the ability of blood to flow to the heart, and heart muscle dies.
• Cardiac arrest, or sudden cardiac death (SCD), is NOT a heart attack, but a prior heart attack can put someone at risk for SCD.

When is ICD therapy the right choice?
In the simplest terms, anyone who has had or is at a high risk of having ventricular tachycardia, fibrillation or sudden cardiac arrest is a candidate for an ICD. People at highest risk are those whose heart pump function is low, caused by prior heart attack, valve disease, or other causes. Heart pump function is measured painlessly with a brief test. This is usually an echocardiogram, which is a sonogram of the heart, performed in a cardiologist's office. It is indicated for patients who have had a heart attack in the past or who have symptoms possibly suggestive of decreased heart pump function, such as shortness of breath, or extreme fatigue. Heart pump function is determined by a number called the Ejection Fraction, or EF. The EF is the percentage of blood that is ejected from the heart with each heartbeat, and is normally above 50%. People who should be considered for ICD implant to prevent sudden cardiac death are those with EFs less than or equal to 35%. Many people have both coronary artery disease (the primary cause of heart attacks) and an arrhythmia (a heart rhythm disorder). They are at particular risk for sudden cardiac death and may be candidates for ICDs, even though they have no noticeable symptoms of an abnormal heart rhythm.

A cardiac arrhythmia specialist should evaluate cardiac patients if they have experienced any of the following:

• A prior cardiac arrest
• Ventricular tachycardia (VT) which is an episode of rapid heartbeat originating from the lower chambers of the heart
• Ventricular fibrillation (VF), which is similar to VT but is characterized by a heartbeat that is too rapid and is irregular or chaotic
• Ejection fractions of less than 35 to 40 percent. An ejection fraction (EF) is the proportion, or fraction, of blood pumped by the heart with each beat. A normal heart pumps out a little more than half the heart's volume of blood with each beat, making a normal EF 55 percent or higher
• Patients at a high risk for sudden cardiac death (SCD) because of an inherited heart abnormality.

How is an ICD implanted?
The cardiac electrophysiologists of Associated Cardiologists implant the ICD. These are cardiologists with specialized training in the diagnosis and treatment of heart rhythm disorders.