Cryoablation

New Technology "Freezes" Out Irregular Heartbeats

by Jim Evans

The normal resting heart rate for an adult is usually between 50 and 100 beats per minute. However, irregular heart rate — or arrhythmia, as it is most often called — where the heart beats too fast, too slow, or with a skipping (irregular) rhythm, is not uncommon.

In fact, the heart rate can be affected by even minor day-to-day factors in our lives such as smoking, caffeine, alcohol consumption, certain dietary supplements, stress, pain, pregnancy, exercise, and other factors. Even healthy children can have extra heartbeats.

However, more than 2.5 million people in the U.S. are affected by atrial fibrillation, an irregular heart rate accompanied by other symptoms such as chest pains, weakness, shortness of breath, lightheadedness or fainting, which can be a sign of a serious heart problem such as heart disease, heart failure, or even a heart attack or stroke.

There are more than 5 million heart failure patients (also known as congestive heart failure or CHF) in the United States with irregular heart rates, and more than 550,000 new cases are reported every year.

Statistically, 80 percent of men and 70 percent of women under age 65 diagnosed with heart failure will die within eight years of sudden cardiac arrest — six to nine times the rate of the general population — so effective treatments for irregular heart rate are critical.

The preferred treatment for many types of rapid heart rate is known as radio-frequency ablation. This is a nonsurgical procedure where a catheter cauterizes those small areas of the heart causing the rapid heartbeats with mild, painless radio-frequency energy that cause the heart muscles in those areas to die.

According to the American Heart Association, radio-frequency ablation has a success rate of more than 90 percent with a low risk of complications. The procedure causes little or no discomfort and is conducted under mild sedation with local anesthesia. Patients usually can resume normal activities in a few days.

However, a new technology — cryogenic ablation or cryoablation — might replace radio-frequency ablation in the future. It already is being tested on patients at Iowa Methodist Medical Center and the Iowa Heart Hospital at Mercy in Des Moines, and at four other nationally known U.S. centers ("Squeezing out irregular heartbeats," Heartbeat, Vol. 19, No. 1 – Winter 2004). The new procedure "freezes" the critical area of the heart with catheters cooled to minus 80 degrees Celsius to eliminate the abnormal fluttering or quivering of the heart.

Dr. Robert Hoyt, a cardiologist at Iowa Methodist Hospital, is only the second physician in the United States to treat a patient with the system, more than two years ago. Although Hoyt says cryoablation has been approved by the U.S. Food and Drug Administration, it may be years before approval is given for widespread use.

According to Hoyt, primary advantages to cryoablation are as follows:

• It is totally painless.

• There is little chance of inadvertent damage of the pulmonary veins where atrial fibrillation usually originates.

• There is less chance for clotting in the heart.

There is also the additional advantage of greater control over the ablation instrument than with the traditional radio-frequency ablation, and it allows the cardiologist to treat problems that radio-frequency ablation cannot reach.

Hoyt said he expects radio-frequency ablation will continue to be used more frequently than cryoablation for now.

"The conditions for which we do well with radio-frequency ablation, we will continue to do," he said. "In those areas where radio- frequency energy has limitations, we’ll use the cryoablation approach."

The next generation of cardiac-care technology already has become a reality.