Electrophysiological Risk in Pediatric Intermittent versus Persistent Ventricular Pre-excitation: A Large Single-Center Cohort

The human heart beats with a rhythm that is usually reliable, but in some people, an extra electrical wire connects the upper and lower chambers. This extra connection, known as an accessory pathway, can sometimes cause the heart to beat too fast or skip a beat. In a small number of cases, this extra wire can allow a dangerous, chaotic rhythm called atrial fibrillation to conduct electricity too quickly to the lower chambers, potentially leading to sudden cardiac arrest. Because of this risk, doctors often need to decide which children with this extra wire are safe to watch and which ones need a procedure to remove the wire. For decades, doctors have looked for clues on a standard heart tracing to make this decision. Two of the most common clues are whether the extra wire shows up constantly on the tracing or only sometimes, and whether the child has ever felt symptoms like a racing heart or fainting. The medical community has long suspected that if the extra wire disappears on the tracing or if the child feels fine, the wire is likely safe.

A large study from a single hospital in Turkey set out to test these assumptions in a group of 917 children, aged 18 and under, who underwent a detailed electrical mapping of their hearts. The researchers wanted to see if the way the extra wire behaved on a standard heart tracing or the presence of symptoms could accurately predict if the wire was dangerous. They defined a dangerous wire as one that could conduct electricity very quickly, a property measured by specific electrical tests performed while the child was sedated. The study found that while an extra wire that appears only intermittently on a heart tracing is generally safer than one that is always visible, it is not safe enough to ignore. About 15 percent of the children with these intermittent wires still had electrical properties that placed them at high risk. Furthermore, the study showed that feeling fine or having symptoms made no difference in predicting danger. Children who had never felt a symptom were just as likely to have a dangerous wire as those who had experienced palpitations or fainting spells.

The researchers also looked at the physical location of these extra wires, particularly in children who needed a second procedure because the first attempt to remove the wire failed. They discovered that wires located on the right side of the heart were the most common reason for needing a repeat procedure. This suggests that the difficulty in removing a wire is often about where it is located and how stable the tools can be in that spot, rather than how fast the wire conducts electricity. The study concludes that while an intermittent extra wire is a good sign, it does not guarantee safety, and the absence of symptoms does not mean a child is free from risk. Doctors must look at the whole picture, including detailed electrical tests, rather than relying on a single clue from a standard heart tracing or the patient's history of feeling ill.

In this study, the team analyzed data from children who underwent a primary electrophysiological study, which is a procedure where doctors insert thin wires into the heart to map its electrical system. They compared the electrical measurements of children whose extra wires showed up constantly on their heart tracings against those whose wires appeared and disappeared. The results confirmed that children with intermittent wires had longer recovery times for their electrical pathways, which is a sign of a slower, safer conduction speed. However, the researchers found that 15.2 percent of the children with intermittent wires still met the criteria for high risk, meaning their wires could still conduct electricity fast enough to be dangerous. This number is significantly lower than the 36.9 percent found in children with persistent wires, but it is high enough to mean that doctors cannot simply assume an intermittent wire is harmless.

The study also addressed the role of symptoms. Many parents and doctors assume that if a child has never felt their heart race or fainted, the extra wire is benign. The data from this large group of children proved this assumption wrong. The researchers found that the rate of dangerous electrical properties was nearly identical between children who had symptoms and those who had none. In the group with persistent wires, about 36.5 percent of symptomatic children had high-risk features, compared to 37.5 percent of asymptomatic children. The same pattern held true for the intermittent group, where 15.3 percent of symptomatic children and 15.0 percent of asymptomatic children had high-risk features. This means that the absence of symptoms is not a reliable way to rule out a dangerous pathway.

When examining the children who required a second procedure, the researchers found a different pattern related to anatomy rather than electrical risk. Right-sided pathways, which are located on the right side of the heart, accounted for 60 percent of these repeat procedures. This high rate of recurrence on the right side is likely due to the technical challenges of reaching and stabilizing tools in that specific area, rather than the wire itself being more dangerous. The study highlights that the difficulty of removing a wire and the risk of the wire causing a sudden cardiac event are two separate issues. A wire can be hard to remove because of its location but still be electrically safe, or it can be easy to remove but still conduct electricity dangerously fast.

The findings from this study suggest that the current practice of using intermittent pre-excitation or the lack of symptoms to clear a child of further risk assessment may be insufficient. While an intermittent wire is a favorable sign that lowers the probability of danger, it does not eliminate it. Similarly, a child who feels perfectly healthy may still harbor a pathway capable of rapid conduction. The researchers emphasize that decisions about whether to perform an invasive electrical study should be made by considering the entire clinical context, including the child's age, the specific pattern of the extra wire, and any associated heart conditions, rather than relying on a single factor. This approach ensures that children who might be at risk are not missed, while also avoiding unnecessary procedures for those who are truly safe.