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Implanted microchip could help prevent stroke


By Dennis Thompson
Health Day reporter

WEDNESDAY, June 9, 2021 (HealthDay News) – Norman Mayer, 86, walks around with a computer chip in his chest and doesn’t think about it at all.

Doctors implanted a tiny heart monitor chip in Mayer’s chest after suffering a mini-stroke in late 2015, to track his heartbeat and potentially detect an irregular heartbeat called atrial fibrillation (a-fib).

“You don’t even know he’s there,” said Mayer, sitting mayor of the Alberta community of Camrose in Canada for 32 years. “You don’t mind. It’s right there and it’s part of life.”

But thanks to the chip, doctors were able to better track Mayer’s heartbeat and adjust his medication to prevent him from having another stroke, he said.

Mayer was involved in one of two new clinical trials that show implantable heart monitor chips are much more effective at detecting irregular heart rhythms than external devices now more commonly prescribed after stroke.

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One trial showed that the implanted monitor detected three times more atrial fibrillation than an external device that patients have to carry, and in the other trial, it detected six times more atrial fibrillation.

The results represent “a dramatic increase in the frequency at which we have detected atrial fibrillation,” said Dr. Brian Buck, principal investigator of one of the clinical trials and stroke neurologist at the University of Alberta.

Atrial fibrillation increases a person’s risk of stroke four to five times, and at least one in seven strokes is caused by an irregular heartbeat, according to the United States Centers for Disease Control and Prevention.

The jerky heartbeat causes blood to pool and clot in the upper chambers of the heart. If a clot goes to the brain, it triggers a stroke.

“We know a-fib is a high risk stroke disease,” said Dr. Dawn Kleindorfer, chair of neurology at the University of Michigan School of Medicine. “We know that treating a-fib with anticoagulation reduces your risk by up to 80%. “

The problem is, atrial fibrillation is a lot like the noise your car makes – you can’t rely on the noise that will occur when the car is inspected by a mechanic.

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Buck explained that “the rhythm disturbance can be present for a few minutes in a month, then not appear for several months later, then only be there for a few hours and then go away again.”

Stroke victims are typically given a portable monitor the size of a deck of cards to carry around for 30 days, he noted. They put sticky electrodes on their chest which are connected to the monitor, which constantly records their heartbeat.

But a month of monitoring is usually not enough, and patients find the external monitor to be a real pain in the neck, Buck said.

“They actually hate carrying the loop recorder around,” Buck said. “Thirty days with an external box with you is really hard. It has a big impact on your ability to exercise, work, that sort of thing.”

So, two different research teams decided to test whether an implanted device would work better to track heart rhythms. The implant can track the heart rate for up to three years and is not a problem for patients.

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Mayer said implanting the device was a snap.

“It’s okay,” Mayer said. “I went one morning and they just took a little sharp knife and cut a piece of you, slipped this thing into your chest, put a bandage on and told you to go home.”

A monitoring station kept on a counter delivered the data captured by Mayer’s chip to the hospital, where neurologists analyzed it for signs of atrial fibrillation.

“I never got a call because of the fluctuations, but I had discussions quite regularly with the girl who was responsible for it,” Mayer said. “They could monitor different peaks at different times of the day, depending on my activities or whatever. As such, they were using it to adjust my medications, for blood thinners, and for hypertension.”

Buck’s team found that doctors were able to detect signs of a-fib in 15% of patients with the implant, compared to 5% with the external monitor, among 300 people who had recently had a stroke. .

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The other team, led by Dr. Richard Bernstein of Northwestern University Feinberg School of Medicine in Chicago, performed even better.

The chip detected atrial fibrillation in 12% of patients, compared to about 2% detected by external cardiac monitoring, in nearly 500 recent stroke victims.

The implantable chips are approved for use in the United States and Canada, but still face hurdles, experts said.

Implanted device used in trial in Alberta Implanted device used in trial in Alberta

In Canada, the national health care system demands that a device be cost effective before the government pays for it, Buck said.

The implant costs more than $ 5,000 per patient, compared to about $ 1,000 for the external monitor, the researchers said in briefing notes.

“Before our healthcare system is ready to pay for a device that costs several thousand dollars, we have to show that it is cost effective,” Buck said. “Not only will it detect atrial fibrillation, it will actually reduce stroke rates and improve the quality of life for patients and benefit the health system as a whole.”

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The same goes for coverage from insurance companies in the United States, which often balk at both the expense of the device and the cost of cardiologists who have to examine the data for signs of a-fib. , Kleindorfer said.

“A cardiologist somewhere has to read them over and over again,” Kleindorfer said. “The downsides are more on the insurance side and the financial side, but to me it is clear that you find more a-fib with the implantable monitor than with the external one.”

Neither clinical trial was large enough to show the devices actually prevented strokes, Kleindorfer and Buck noted. More research will be needed to prove that implants can better protect people against stroke.

However, the current evidence is strong enough that the American Heart Association recommends a-fib surveillance in its recently updated guidelines for secondary stroke prevention, said Kleindorfer, who was the lead author of the guidelines. .

“In my head as a clinician, of course I would like to make the monitor implantable rather than the external one because I find more fib-a and I put them on more anticoagulation, which should reduce their risk of stroke,” said Kleindorfer.

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Both clinical trials were recently published in the Journal of the American Medical Association.

More information

The US Centers for Disease Control and Prevention has more on atrial fibrillation.

SOURCES: Brian Buck, MD, PhD, stroke neurologist, University of Alberta, Canada; Dawn Kleindorfer, MD, president, neurology, University of Michigan School of Medicine, Ann Arbor; Norman Mayer, 86, Camrose, Alberta, Canada; Journal of the American Medical Association, June 1, 2021

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