DALLAS, Sept. 2 -- Burning out damaged heart tissue through a procedure called ablation sharply reduces the number of shocks delivered by implantable defibrillator to slow down racing hearts, a new study reports in today's American Heart Association journal Circulation.
Implantable defibrillators (or ICDs) are devices the size of beepers implanted in the chests of people with heart disease who are at risk for cardiac arrest because of ventricular tachycardia, a racing heart. It is a miniature version of the electrode paddles used in emergency rooms to organize heartbeats. If the ICD detects a rapid heart rate, it provides an electric shock to the heart to slow it down to a normal rhythm.
In 1995, about 17,000 patients receive the ICDs, frequently after surviving a heart attack. Physicians consider it very effective therapy and data show it prolongs life.
"The shocks can be very unpleasant," says Adam Strickberger, MD, lead author of the journal article. "Patients describe a whole gamut of symptoms, from being hit in the chest with a baseball bat to not even knowing they had a shock."
Patients who are treated by the defibrillators often - several times a day or a week - frequently suffer both pain and anxiety. To reduce the number of shocks, physicians prescribe antiarrhythmic drugs. Since these patients are very sick, Strickberger says, they could end up taking eight to ten pills a day, and these drugs do not always work.
"Ventricular ablation" improves the quality of their lives, the scientists at the University of Michigan found. The research suggests that abla
tion should be used more frequently. Twenty-one patients with coronary heart disease and ventricular tachycardia, 17 men and four women, participated in the Michigan study. All had heart attacks. Their mean age was 69. All had ICDs and found that drugs were not working for their tachycardia.
The researchers performed radiofrequency ablation, a relatively common and effective procedure in which a catheter is inserted into the ventricular chamber of the heart and a small amount of damaged tissue is burned out.
Some had more than one procedure. In five patients, the ablation was not successful. Only one patient suffered a complication, a complete heart block, treated with a dual-chamber pacemaker.
After the procedure, the patients were monitored in the hospital and given the same antiarrhythmic drug therapy as before. After release, they were monitored as outpatients; the researchers used a computer attached to the ICD to read how many times the devices fired off.
The number of ICD therapies was significantly reduced, the research found, dropping from an average of 59 shocks per month per patient to less than one.
Within a month of the last follow-up visit, the quality of life was assessed by means of two telephone questionnaires, one for the period before the ablation, the second for the most recent month. Patients responded on a scale of one to five, with five being the highest level of concern, the one the least. They were asked if they agreed with statements such as: "I worry about the ICD firing and creating a scene," or "It bothers me not knowing when the ICD will fire."
"These results suggest that improvement in quality of life occurs after successful ablation of ventricular tachycardia in patients receiving frequent ICD therapies, but not in patients with an unsuccessful ablation procedure," Strickberger says.
In an accompanying editorial in Circulation, William G. Stevenson, MD, of Brigham and Women's Hospital in Boston, stated the reliability of the quality of life assessment "is diminished by the fact that the questionnaire for both the preablation and postablation periods was administered only after the ablation procedure."
Also, he wrote, there was no control group, but that was likely, as the researchers admitted, because it would have been difficult to recruit one. The patients were receiving multiple shocks from the defibrillators and would have been asked not to alter their therapies.
Stevenson agreed with the authors that "further investigation is required to determine whether ablation should become a major adjunctive therapy to the ICD safety net."
Circulation is one of five journals published in Dallas by the American Heart Association.
Media advisory: Dr. Strickberger can be reached at (313) 763-7392. (Please do not publish telephone numbers.)