Ian Law, M.D., a pediatric cardiologist at University of Iowa Children's Hospital, says heart defects are the most common type of birth defect and affect as many as eight per 1,000 children. "Arrhythmias are less common and affect around one in every 1,000 newborns. Given that there are approximately 40,000 live births in Iowa each year, there will be around 320 newborns who are diagnosed with heart disease, and 32 infants who are born with an abnormal heart rhythm," Law says.

Some times the diagnosis is made prior to birth when an abnormally fast or slow rhythm is noticed on a routine pre-natal ultrasound. More commonly, Law says, an abnormal heart rhythm is noted while the newborn is being monitored in the newborn nursery or during a follow-up examination in their doctor's office.

"When a child has an abnormally fast or slow heart rhythm for a period of time he can develop rapid breathing, appear more tired than usual, and have difficulty feeding. This can be what prompts the parents to go to their doctor's office for evaluation," Law says.

For pediatric patients with abnormally fast heart rhythm, medical management can be initiated right away. "When an abnormally fast heart rhythm is diagnosed prior to birth, medications are given to the mother to control the fetus' heart rhythm, otherwise medication is given directly to the infant. If the infant has a very slow heart rate that's causing significant compromise, a pacemaker is needed and is usually implanted within a day or two," he says.

The majority of arrhythmias in infants and children are abnormally fast heart rhythms and the vast majority respond to medications. Pacemakers are used to treat the abnormally slow heart rhythms. On very rare occasions, Law says, children are born with life-threatening abnormally fast rhythms that require medications, and at times, a defibrillator (a device placed inside the body that can shock the heart into a normal rhythm).

"When an infant is diagnosed with an abnormally slow heart rhythm, such as complete heart block, a pacemaker is required for the rest of his life. In general, pacemaker batteries last anywhere between four and eight years, sometimes longer. Therefore, these patients will have to undergo numerous pacemaker battery replacements throughout their lifetime," he says. The battery change is a relatively straightforward surgery.

For patients diagnosed with abnormally fast heart rhythms in the newborn period, many will outgrow their abnormal heart rhythm within the first six to 12 months of life, and therefore not require long-term medical management, Law says.

"Patients who have a recurrence of their abnormal heart rhythm after their first year of life tend to continue having fast heart rates off and on throughout their life. In these cases, medications are often given until the patient is of an adequate size and age to undergo a heart catheterization procedure.

"During the heart catheterization, catheters, similar to wires, are inserted through the veins in the leg into the heart to determine the cause of abnormal heart rhythm. During the heart catheterization an ablation procedure can be performed to get rid of the abnormal tissue causing the abnormal heart rhythm.

"To give you a better understanding of what this involves," Law says, "one can envision an abnormal heart rhythm in a child as a car racing around a race track. The goal during the heart catheterization procedure is to create a road block on this race track so the abnormal heart rhythm cannot continue to loop around. The catheter ablation procedure has a success rate around 95 percent, and the children usually go home the same day as the procedure.

"When a patient has a pacemaker implanted for an abnormally slow heart rhythm, he can usually return to almost all the activities as other children in his age group. We generally restrict them from playing contact sports, such as football or hockey, as this may cause damage to their pacemaker.

"Obviously, some patients with pacemakers or defibrillators also have other significant heart disease and therefore their activity level is not necessarily restricted by their abnormal heart rhythm and pacemaker, but by their heart defect.

"For those patients with abnormally fast heart rhythms, taking a medication to control the arrhythmia will often allow the children to participate in regular activities. Following a catheter ablation procedure, we allow children to return to all their regular activities, including competitive sports, within one week," Law says.

A tremendous number of advances have taken place for the treatment of children with abnormal heart rhythms in the last five to 10 years. "A concerted effort has been made into making pacemakers, and the leads that attach to the heart, smaller so they can be implanted in children and newborns.

"For the treatment of fast heart rhythms, the catheter ablation procedure has been around for more than 15 years, although advances in catheter technology have made this treatment option much more feasible in smaller children.

"In general we perform these procedures on an elective basis once the children reach four years of age or 30 pounds. Initially, radiofrequency energy was used to destroy the tissue by heating it to very high temperatures. In the last several years, newer catheters have been developed that use cryothermal energy, creating extremely cold temperatures to destroy the abnormal tissue.

"The advantage of this cryothermal technique is that at moderately cold temperatures, the effects are completely reversible. An additional advantage of cryothermal catheters is that the cold catheter tip sticks to the area of interest, like a tongue sticks to a flag pole in winter, making the procedure much more precise. Obviously this is a tremendous advantage in children when the margin of error is much smaller," Law says.

For more information:

Ian Law, M.D.

University of Iowa Children's Hospital

Catheter Ablation