Cardiac Connection > Diseases & Conditions > When your heart is racing faster than you are

When's the last time you felt your heart race? On a ride on Space Mountain? In a job interview? During the last five minutes of the Super Bowl?

A rapid heartbeat can be a sign of excitement, even joy. But if your heart muscle has been weakened by a heart attack, heart disease or other condition, a fast heart rhythm can lead to sudden cardiac arrest. Fortunately, patients at risk of sudden cardiac arrest now have a variety of treatment options including implantable cardioverter defibrillators (or ICDs) that can correct fast, life-threatening heart rhythms automatically.

"Research shows that patients who receive defibrillators can decrease their chance of dying from sudden cardiac arrest by 21 to 33 percent," says Doylestown Hospital electrophysiologist Stephen Sloan, MD. The ICD has become the treatment of choice for patients at risk and is routinely covered by Medicare.

Recent research has identified many more patients in need of an ICD. In the past, a patient had an ICD inserted only if he had survived a cardiac arrest or if tests found his heart could go into an abnormal rhythm. Today, a patient may be referred for an ICD if his heart muscle does not perform well on a daily basis or during routine activities. Sophisticated testing allows physicians to measure the heart's "ejection fraction," or the amount of blood that the heart's left ventricle is pumping out per heartbeat.

"An ejection fraction of less than 36 percent may indicate the need for an ICD," says Dr. Sloan.

The most common diagnostic test to assess ejection fraction is an echocardiogram, or ultrasound of the heart. Most physicians recommend periodic echocardiograms for patients with heart disease. For others, the warning signs of weakened heart muscle include blackout spells, heart palpitations, a racing heart, shortness of breath, swollen feet and extreme fatigue.

Only the size of a personal pager, the life-saving ICD is usually implanted under the skin near the left collarbone, much like a pacemaker. One, two or three flexible wires, or leads, run through the veins to the lower chambers of the heart and continuously monitor heartbeat. The procedure involves local anesthesia and an overnight hospital stay. If the ICD detects a dangerously fast heartbeat, it delivers a brief electrical shock that restores the heartbeat to normal. The shock can vary in intensity from a fluttering to a kick in the chest, depending on the situation.

Today's ICD is smaller and more comfortable, and the batteries last longer, about five to seven years. Progress continues, says Dr. Sloan. For example, in the future, remote monitoring will allow the physician to check the ICD daily from the patient's home.

Signs of cardiac arrest:

Sudden rapid, chaotic or abnormally slow heart rhythms that cause the heart to stop beating altogether
Victim collapses
Unresponsive to gently shaking
Normal breathing stops
No blood pressure
No pulse