Implantable Cardiac Monitor

The Great Detective Game

Wesley Rea planting flowersThe device placed in Wesley Rea’s chest at Milford Regional may only be one third the size of a AAA battery, but the tiny heart monitor could provide clues about the mysterious sensations that occasionally strike the 53-year-old Franklin resident. “At the time, it’s extremely overwhelming,” the father of three says, describing the fleeting sense he gets every now and again that he might pass out.

Answers to cases like Rea’s are often elusive, so his cardiologists turned to a new tool for their investigation: the Reveal LINQ, Medtronic’s latest under-the-skin heart monitor and the smallest one on the market. This past spring, Dr. William Shine of Hopedale Cardiology inserted the new device into Wesley, making Milford Regional the first hospital in Massachusetts to use the Reveal LINQ after the federal Food and Drug Administration approved it.

All cardiac monitors record the electrical impulses controlling the heart, and are used when patients like Rea experience dizziness, palpitations, feinting or chest pain. The devices look for episodes when the heart beats too quickly, too slowly or irregularly — disorders called arrhythmias. Some are harmless; others are life threatening.

Like other cardiologists, Dr. Shine and his colleagues talk to patients about their symptoms and family histories. They also look for structural problems in the heart and its valves. But they often want to record the electrical impulses as well. In the past, doctors wanting to go beyond the brief snapshots produced by electrocardiograms, or EKGs, had one choice: wearable external monitors, often called Holter monitors. The devices provide monitoring for up to 30 days, but depend on proper placement and connections. They are cumbersome and not waterproof, leaving data gaps when patients take them off to shower or sleep.

They tend to remove them at other times, too — either because they’re confused (in the case of some elderly patients), or they’ve grown weary of the bulky monitor, the tangle of wires, the sticky electrodes and the annoying beeps.

That’s where implantable monitors come in. While external monitors are still cost-effective for assessing treatments or studying frequent and predictable symptoms, devices that go under the skin are less intrusive and provide longer, uninterrupted monitoring. That’s important when symptoms pop up at irregular intervals — sometimes only once or twice a year. “External monitors do work,” Dr. Shine says. “They’re just not nearly as accurate or as sensitive or as effective.”

While Milford Regional cardiologists have only used the Reveal LINQ since March, it has already helped them with a patient who complained of a racing heart. They didn’t want to prescribe medication without good reason, as previous tests had never pinpointed a problem. The monitor showed he had a dangerous arrhythmia called atrial fibrillation — a rapid and irregular contraction of the heart’s upper chambers that can increase the risk of stroke. It’s treatable, but many people don’t realize they have it.

In Wesley’s case, it’s actually unclear if he has a cardiac problem or not — he could have a neurological issue or something else entirely. But the first step is to look at the heart. He came to Hopedale Cardiology after a series of episodes. The first couple of times, it felt like someone had punched him in the chest and that for a second or two he might pass out. He had passed out years ago but received a diagnosis of dehydration from a cardiologist, so he didn’t make much of the latest experiences, at least at first. The strange feelings were intense but also quickly went away. However, with a more recent episode at work, his head got hot, his eyes rolled back and he heard himself make a weird sound. “It went so much further than it had in the past that it really scared me,” Wesley says. An EKG proved normal, but Hopedale Cardiology recommended the Reveal LINQ, and Dr. Shine inserted it in March.

An earlier, larger version of the device required the doctor to create space in the chest, with sutures to close the incision, local anesthesia for pain and conscious sedation at times to relieve anxiety. The new cardiac monitor holds 20 percent more data, but is small enough to get injected through a 1-centimeter incision using a special syringe-like tool. Wesley’s procedure took less than a minute, with just a little numbing agent and a bandage.

While the device provides continuous wireless monitoring, it does not actually record every second. Instead, it is programmed to detect and save abnormal patterns, and automatically alert doctors at critical thresholds. Wesley also carries a pager-sized gadget that he or someone near him can hold up to his chest when there are problems, prompting the monitor to save the previous 90 seconds and the following 90 seconds. Data is transmitted from Wesley’s home to Hopedale Cardiology through a base like that for a portable phone. The point is to capture three information sets: when he feels fine but is actually experiencing cardiac problems, when he rightly knows he’s having trouble and when he senses something but it turns out unrelated to the heart.

Wesley has used the signaling device, but he’s also seen the base transmitting data when he’s felt fine. The device has recorded five or six times between March and the end of May because of prompts or its automated response, including the capture of isolated, extra heartbeats — not normal but not uncommon.

At this point, they are collecting valuable data in hopes of diagnosing Wesley's problem; and they have time — the monitor’s battery lasts three years. Until then, it’s at least guarding against any dangerous episodes that might arise.

“It’s the great detective game,” Dr. Shine says, calling Wesley’s diagnosis a work in progress. “But we can be confident and he can be confident that he’s not at risk.”

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