Practical solutions to improve treatments for heart rhythm disorders in children

By Lennart ’t Hart

As a physician at the Willem-Alexander Children’s Hospital at LUMC, Bertels regularly sees and treats children with arrhythmias. Some children have hearts that beat too fast, others too slow, or irregularly. “These complaints interfere with their daily lives: they no longer dare to play sports or are afraid to leave the house,” he explains.

He carried his clinical experiences into his research. In his PhD study, he focused on three key questions:

1. How can we treat arrhythmias without using x-ray radiation?
2. Which medications are truly effective against arrhythmias originating in the ventricles?
3. And how can we reduce the number of shocks in children with an implanted defibrillator (ICD)?

1. Reducing radiation in arrhythmia treatment

A common heart condition in children is supraventricular tachycardia (SVT), a collective term for arrhythmias that start in the atria or the AV node. In these cases, the heart beats too fast. If medication fails, doctors can perform an ablation, disabling the part of the heart that causes the arrhythmia.

Traditionally, ablations relied on X-ray imaging to visualize the heart and catheters. But radiation can be harmful in the long term, especially for children whose bodies are still developing.

A safer alternative

At LUMC, doctors now use electro-anatomical mapping (EAM), which determines catheter positions via magnetic or electrical sensors. “A computer shows exactly where the catheters are, allowing us to pinpoint the arrhythmia and display it on a screen,” says Bertels.

His research shows that EAM is just as effective as X-ray imaging, but far safer. Radiation exposure is reduced to about one-fifth of the original level. “This means the procedure can safely be performed even in infants, whose hearts are the size of a walnut,” he notes.

2. More effective medication for ventricular arrhythmias

Some children experience extra or skipped beats caused by premature ventricular contractions (PVCs). These are often harmless, but sometimes they impair heart function and require treatment.

Together with colleagues from several university medical centers, Bertels compared the standard drug metoprolol with flecainide, a medication less commonly used for PVCs. In his study, children received both drugs in sequence, while their heart rhythms were continuously monitored. He combined these findings with data from earlier studies.

A drug that makes a difference

Results showed that flecainide reduced extra beats far more effectively than metoprolol. In children whose heart function was impaired by arrhythmias, flecainide restored normal pumping capacity. These insights are significant, since flecainide is not usually prescribed as a first choice for children with PVCs.

“For years we prescribed metoprolol, but it hardly worked. Flecainide proved much more effective in half of the children. That’s a big difference. It’s wonderful to see a drug we barely used before now truly changing outcomes for children,” says Bertels.

3. Smarter settings for defibrillators

Some children require an implantable defibrillator (ICD), a device that monitors heart rhythm and delivers a shock during dangerous arrhythmias to prevent cardiac arrest. While life-saving, the shock is painful and frightening, often disrupting daily life. “Some children stop exercising after a shock, or sleep poorly out of fear of another one. We want them to live normally, without constant anxiety,” Bertels explains.

To address this, Bertels collaborated with colleagues at Erasmus MC and Amsterdam UMC to investigate whether shocks could be reduced without compromising safety. He analyzed studies on ICDs in children and adults, and collected data from 116 children with ICDs before and after 2010, focusing on shock frequency and device settings.

Preventing unnecessary shocks

He concluded that shocks can safely be reduced by adjusting ICD settings—for example, raising the threshold heart rate that triggers a shock and using remote monitoring.

“An unnecessary shock is extremely traumatic for a child. By choosing smarter settings, we can hopefully prevent that,” Bertels says. Larger studies are still needed to confirm these results.

From practice to science

Bertels’ research demonstrates the potential of new techniques, better medication, and smarter device settings to improve care for children with arrhythmias.

His findings are already being applied at LUMC. Doctors now use EAM during ablations, reducing radiation exposure. Flecainide has replaced metoprolol as the preferred treatment for PVCs. ICD programming has also been adjusted, with higher thresholds and longer delays to minimize unnecessary shocks. These changes are based on data from multiple hospitals, including Erasmus MC and Amsterdam UMC, and are being adopted there as well.

International interest

Bertels’ work has attracted attention abroad. At conferences, he frequently receives questions from international colleagues, including American physicians interested in flecainide use.

His research shows how clinical observations can lead to targeted solutions. By focusing on children’s needs and what happens in the consultation room, LUMC has been able to implement concrete improvements in treating pediatric arrhythmias.