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Pacemakers too big for children, wireless devices better but risky

Pacemakers, used by many patients with irregular heart rhythms, are not built for children, and do not mesh well with growing bodies, say scientists, pointing out that scrambling up trees, hanging from monkey bars, or the simple act of growing, make the devices more likely to fail.

Traditional pacemakers have wires, or leads, that send electrical pulses to a slow-beating heart, and these, they add, aren't designed for a growing body, being mainly targeted at older people.

Roughly one in 15 000 children are born with congenital heart block, causing an abnormally slow heart rate, which leads to lightheadedness, shortness of breath and, in serious cases, heart failure.

Medications work in the short-term, but for children with more severe symptoms, pacemakers are the most reliable, durable treatment – though one fraught with risks, reports STAT News.

However, the amount of physical activity children do far exceeds that of a 60- or 70-year-old, according to Maully Shah, director of cardiac electrophysiology at the Children’s Hospital of Philadelphia.

More than 70% of people with pacemakers are at least 65.

“None of these is really tested when they’re manufactured to accommodate for growth,” said Shah, who suspected that wireless pacemakers, implanted directly in the heart via catheter, might fare better in children’s bodies than the more traditional, wired devices.

So she and a team of paediatricians set out to look at the performance of wireless pacemakers in children with slow heartbeats across the globe.

In their research, the results of which were published in Circulation: Arrhythmia and Electrophysiology, a journal from the American Heart Association, they concluded that wireless pacemakers may work in children just as well as they do in adults, at least in the short term. But they concluded that until device makers create catheters that fit children’s veins, they can’t be widely used.

“Everything’s easier in a bigger person,” said Anne Dubin, head of the paediatric cardiology division at Stanford Medicine Children’s Health. “Once you get to smaller, more fragile blood vessels and tissues, your risks increase.”

The study is not an official clinical trial; but rather a retrospective analysis of real-world data. Physicians across 15 health centres implanted the wireless pacemakers in 63 children over a five-year period. Almost all of the children had successful implantations.

The pacemaker remained effective over a follow-up period of 10 months, and in at least a third of patients, for more than a year. Ten children experienced complications; most were due to minor bleeding, but three were major, including a blood clot and perforation of the heart.

At the time of the study, just one wireless pacemaker had earned FDA approval: Medtronic’s Micra pacemaker. The device makes up a minority of pacemaker implantations: some 3m Americans have pacemakers, and just more than 100 000 patients have received the Micra device worldwide. It has risks, the most serious being poking tiny holes in the heart.

Still, the technology is gaining traction, at least in adults. Another wireless pacemaker from Abbott received FDA marketing approval in 2022.

Shah sees promise in the device. But the catheters required to implant the pacemaker are often too large for children, and could cause grave complications.

“You’re working in a very small space – a paediatric heart,” she said. “The target is very small and the equipment very large.”

Another issue is that the only way to extract the device is through surgery. When pacemaker batteries die, physicians can either implant an additional one or replace it completely. This is less of a big deal in older patients, who might require just one or two pacemaker replacements in their lifetime. But a child will go through many pacemakers in their lifetime.

A small heart can fit only a finite number of pacemakers, and removing pacemakers surgically can cause serious harm.

“Whenever we do anything with children, we really have to think about their future,” Shah said. “Not just the implant at the time of the procedure, but how that is going to perform for a remainder of a child’s life.”

Dubin, who was not involved with the study, echoed Shah’s concerns about the current risks of implanting wireless pacemakers in children. She’s cautiously optimistic, but wants to see more long-term results before using the pacemakers at scale.

While Medtronic’s pacemaker fits in children, both Dubin and Shah said the device should be miniaturised even further. The device may be too big for some hearts, sticking through and causing leakiness in the heart’s right valve.

Dubin and Shah are both working to push the industry and the US Food and Drug Administration (FDA) to invest in paediatric device development in general. Few children require medical devices, so there’s little financial incentive for industry to invest in paediatric devices.

Children make up a small sliver of their potential clientele. They are also hard to find, and thus enrol, in the large clinical trials the FDA requires of high-risk devices like pacemakers. That means paediatricians rely on using devices that have solely been tested on adults. Paediatric electrophysiologists use devices off-label constantly, Dubin said.

Shah plans to continue the study, increasing the cohort of patients and following them for a longer period of time. She hopes it will inspire device makers to catch up with the need for child-friendly devices.

Study details

Transcatheter Leadless Pacing in Children: A PACES Collaborative Study in the Real-World Setting

Maully Shah, Alejandro Borquez, Daniel Cortez, Anthony McCanta, Paolo De Filippo, Robert Whitehill, Jason Imundo, Jeremy Moore, Elizabeth Sherwin, Taylor Howard, Eric Rosenthal, Naomi Kertesz, Philip Chang, Nandini Madan, Steven Kutalek, Benjamin Hammond, Christopher Janson, V. Ramesh Iyer and Matthew Williams.

Published in Circulation: Arrhythmia & Electrophysiology on 11 April 2023

Abstract

Background
Transcatheter Leadless Pacemakers (TLP) are a safe and effective option for adults with pacing indications. These devices may be an alternative in paediatric patients and patients with congenital heart disease for whom repeated sternotomies, thoracotomies, or transvenous systems are unfavourable. However, exemption of children from clinical trials has created uncertainty over the indications, efficacy, and safety of TLP in the paediatric population. The objectives of this study are to evaluate clinical indications, procedural characteristics, electrical performance, and outcomes of TLP implantation in children.

Methods
Retrospective data were collected from patients enrolled in the Paediatric and Congenital Electrophysiology Society TLP registry involving 15 centers. Patients ≤21 years of age who underwent Micra (Medtronic Inc, Minneapolis, MN) TLP implantation and had follow-up of ≥1 week were included in the study.

Results
The device was successfully implanted in 62 of 63 registry patients (98%) at a mean age of 15±4.1 years and included 20 (32%) patients with congenital heart disease. The mean body weight at TLP implantation was 55±19 kg and included 8 patients ≤8 years of age and ≤30 kg in weight. TLP was implanted by femoral (n=55, 87%) and internal jugular (n=8, 12.6%) venous approaches. During a mean follow-up period of 9.5±5.3 months, there were 10 (16%) complications including one cardiac perforation/pericardial effusion, one nonocclusive femoral venous thrombus, and one retrieval and replacement of TLP due to high thresholds. There were no deaths, TLP infections, or device embolisations. Electrical parameters, including capture thresholds, R wave sensing, and pacing impedances, remained stable.

Conclusions
Initial results from the Paediatric and Congenital Electrophysiology Society TLP registry demonstrated a high level of successful Micra device implants via femoral and internal venous jugular approaches with stable electrical parameters and infrequent major complications. Long-term prospective data are needed to confirm the reproducibility of these initial findings.

 

Circulation article – Transcatheter Leadless Pacing in Children: A PACES Collaborative Study in the Real-World Setting (Open access)

 

STAT News article – Wireless pacemakers may work for children with slow heart rhythms — but first, doctors need child-sized catheters (Open access)

 

See more from MedicalBrief archives:

 

KZN surgeons insert world’s tiniest pacemaker into heart

 

FDA warns on cybersecurity vulnerabilities in Medtronic devices

 

Billions paid out in the US to replace defective heart devices

 

 

 

 

 

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