When Zeke was almost 2 months old, his mom took him to the hospital when he began throwing up more than he was eating. Immediately, the doctor knew what was wrong. Zeke’s heart was beating at 285 beats a minute, and later soared to 310 bpm, as the staff worked to slow it down through intravenous medication. A top-end heart rate for children is roughly 220 bpm minus the child’s age in years. Rates faster than that can indicate supraventricular tachycardia (SVT), an abnormally fast heart rhythm caused by an electrical short circuit in the top chambers of the heart. Zeke had SVT.
It was a scary day for Zeke’s family, but SVT is a highly treatable condition that can be treated safely and effectively in children.
“In general, SVT is not life-threatening,” said Peter Fischbach, MD, Director of Electrophysiology at Sibley Heart Center. “It’s mostly just disconcerting and uncomfortable. It’s the unpleasant feeling of having a racing heart rate that you can’t stop.”
The pathways in the heart that support SVT are usually present just as a mother is finding out she is pregnant, at about 8-10 weeks of gestation. But just having these abnormal pathways doesn’t mean that you will have SVT. The faster-than-normal heart rate can show up in utero or at any point in a person’s life thereafter, and doctors are not sure why this occurs. SVT in children is not caused by bad genes or environmental exposures, although some stimulants and street drugs can lead to abnormal heart rhythms. SVT may also be associated with chronic heart disease due to the need for complex surgeries in some children. While SVT can be very disruptive, it is not associated with catastrophic events, such as the sudden death of young athletes.
Children who are diagnosed with neonatal SVT (occurring the first month of life) tend to stop having episodes by their first birthday, and then there is a 50 percent chance of it recurring when the child reaches school age. If SVT is diagnosed for the first time after the neonatal period, there is an 80 to 85 percent chance of it becoming a chronic condition.
SVT is usually well tolerated in infants and babies, and because they can’t tell adults what’s wrong, it may not be obvious that a baby has it. However, if SVT persists for 24-36 hours, the baby’s heart can get tired and stop functioning as well, which can cause him to look peaked and worn out and perhaps stop eating.
The good news is that when the tachycardia is corrected, the baby recovers completely, and all those symptoms resolve,” Dr. Fischbach said.
Three treatment options are available to children with SVT:
- Chronic medication
- Catheter ablation
To treat SVT acutely, patients can try to modulate their own autonomic nervous system by using vagal maneuvers such as standing on their heads, holding their breath or applying ice to their faces. These maneuvers can act as the “brake pedal” on the heart, interrupting the electrical short circuit that is applying the “gas pedal” to the heart rate.
There are also medications that can be used to correct the SVT quickly (given by an iv) and medications taken chronically to try and prevent further episodes. If medications don’t work, or the medications are associated with unpleasant side effects, a catheter ablation may be recommended but usually not until a child is at least 8 years old. The catheter ablation procedure which is an outpatient procedure has become the treatment of choice for children over the age of 8 with SVT.
The field of electrophysiology and the treatment of SVT has changed remarkably with routine outpatient ablation procedures, and Children’s Healthcare of Atlanta has been in the forefront in the past few years, Dr. Fischbach says. Whereas in the late 1980s and 1990s, if you had SVT, you just had to live with it, ablation now offers a permanent cure with a minimal procedural risk.
“One of the reasons I love electrophysiology is that we are dealing with a fixable problem,” Dr. Fischbach said. “Patients can go home completely cured and don’t have problems in the future. There are very few places in pediatric cardiology where you can completely eliminate the problem the patient is having.”
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