Radiofrequency catheter ablation (RFCA) involves threading a catheter with an electrode at its tip into the area of the heart that is causing a patient’s rapid, uncontrolled heartbeats, a condition called tachycardia. Then a mild, painless burst of radiofrequency energy, which is similar to microwave heat, is used to destroy about one-fifth of an inch of heart muscle. Overall, the procedure was about 90 percent effective in treating tachycardia in this study.
“The findings hold great significance for both patients and physicians,” says lead author Andrew D. Blaufox, M.D., assistant professor of pediatric cardiology at the Medical University of South Carolina in Charleston. “Where you have infants with serious arrhythmias, some clinical problems, and who need multiple drugs to control their heart rhythms, ablation is a real alternative.”
The infants who were treated with RFCA were sicker and had more serious heart arrhythmias than older patients. “The fact that infants are often sicker than older children when they have arrhythmias is a compelling reason to find a definitive cure, such as RFCA,” says Blaufox.
Physicians began treating patients with RFCA in the late 1980s. Over the years, success rates have risen and the rate of complications has dropped. Indeed, because the procedure is often more successful than drug treatments, it has become a standard therapy for many arrhythmias in pediatric patients.
However, safety and efficacy issues have remained regarding the use of RFCA in infants. Animal studies, for example, have suggested that in infants, it might adversely affect normal blood flow in parts of the heart. “There have been some reports of greater complications for children under 15 kilograms (33 pounds), and we have a lot of theoretical reasons to be concerned about doing ablation in children so young, whose heart muscle is still developing,” says Blaufox.
However, several things make RFCA desirable for infants, if the procedure is safe. Arrhythmias in infants may cause more problems than in older children, for example, and they are more difficult to treat with medications. Blaufox and his colleagues reviewed records from a database called the Pediatric Catheter Ablation Registry in order to determine why physicians used RFCA in infants, its complications, and its efficacy.
“We simply wanted to find out if doing ablations in very young children was effective and safe,” he says. The researchers compared 137 infants, ages 2 weeks to 18 months, who underwent the procedure between August 1989 and January 1999 with 5,960 patients, ages 19 months to 21 years, who had RFCA between 1991 and 1998. Twenty-eight of the 49 centers submitting results to the database during that period reported performing RFCA on infants.
“We want to find out why infants were having ablations,” says Blaufox. “It seems the procedures in infants are often being done on those who have what is perceived as life-threatening arrhythmias, and only after they have failed medical therapy.” Among the infants in the study, 36.1 percent had congenital heart defects compared with 11.2 percent of the older patients. And 33 percent of the infants underwent RFCA for life-threatening heart rhythms versus 7.7 percent in the older group.
The researchers found no statistical difference between the two groups in RFCA’s effectiveness in treating arrhythmias, although the trend in success favored the older patients, 90 percent versus 87.6 percent in the infants. A total of 12 major and minor complications occurred in the infant group, including one death. The research team found no statistically significant difference in the complication rate between the infant group and the older patients for either total complications (7.8 percent vs. 7.4 percent) or major complications (4.6 percent vs. 2.9 percent).
One reason why the study did not confirm previous reports of more complications in infants may be that it covered five additional years of data. These were years when physicians who had improved their RFCA skills were obtaining better results. However, Blaufox notes that the small number of complications among the infants reduced the statistical certainty of the analysis. “I am not certain that we would have found no difference between the two groups if there had been 100 more infants in the study,” he says.
Success was unrelated to a patient’s weight or age, the size of the medical center where the procedure occurred, or whether or not the patient had a heart defect. “However, more experienced physicians were more likely to perform successful procedures in infants than those with less experience,” says Blaufox.
In both groups, most patients were treated for accessory pathway-mediated tachycardia. In this ailment, heart muscle from the lower pumping chambers sets up an abnormal electrical bridge to the upper chamber that causes rapid heartbeats.
Co-authors are Gary L. Felix, B.S.; J. Philip Saul, M.D.; and participating members of the Pediatric Catheter Ablation Registry.
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