KALAMAZOO, Mich. – It’s about the size and weight of an iPod, it’s implanted in the chest like a pacemaker, and cardiologist Dr. Tim Fischell says it has the potential to prevent as many as 70 percent of the heart attacks that occur worldwide each year.

If, as Fischell expects, the Guardian moves its way through clinical trials to FDA approval within the next three years, it will be the first personal device on the market sensitive enough to monitor the risk of an individual’s heart attack 24-7 – and immediately warn the individual of that risk.

“Every minute it looks at your heart and asks if you’re having a heart attack,” said Fischell, who is director of cardiovascular research at Kalamazoo’s Borgess Medical Center.

Called a “permanently implantable ischemia detection system,” the Guardian has already been approved in Brazil, where Fischell said the government has ordered 2,000 units. In 18 months, he said, it could be approved in Europe.

“This is the most exciting thing I’ve ever done in my life,” he said. “It has the most powerful potential to alter the course and disrupt the diagnosis and treatment of coronary disease than anything I’ve ever been involved in.”

The titanium-encased device is designed to be implanted under the skin just above the heart, much like a pacemaker. Using computer chips, a wire to the heart and a special antenna, it’s able to take readings of heart activity every 30 to 60 seconds.

It compares readings, and if it detects the heart isn’t receiving enough oxygen, it beeps and vibrates in one of two rhythms. One alerts the patient to consult with his doctor and another alerts him to call 911.

Corresponding software allows doctors to read Guardian-generated data as soon as the patient is within eight feet of hospital computers.

Borgess Medical Center announced that first-phase U.S. clinical trials of the product started this month with the implantation of the Guardian in a local patient.

About 25 subjects at five medical centers across the U.S., including five at Borgess, are expected to participate in the study. Phase-two studies are expected to start in 2008 with 2,000 more U.S. participants, half of whom will be implanted with the Guardian.

“I think the crucial thing is that there are patients who present either a heart attack or sudden death,” said Dr. David Holmes, Jr., a cardiologist at the Mayo Clinic in Rochester, Minn., who is overseeing national Phase 1 trials. “This device has the potential to help identify the highest-risk patients so they can indeed get to the church on time so they can be treated.”

Dr. Mitchell Krucoff, a professor of medicine and cardiology at Duke University Medical Center, said the FDA trials will be important to identifying the proper patients for the device and other unknowns.

“The potential of a permanently implanted high-fidelity electrocardiogram device in appropriately selected patients is enormous,” said Krucoff. “This would literally translate the current emphasis on early interruption of heart attacks to shortening the time window of the first therapy in a way that would probably prevent most heart attacks.

“No other approach, from the millions of dollars the American Heart Association has spent on educating the public about heart attack signs to the dollars put into quick-response protocols, has been able to shorten (that) window.”

If the product is approved, Fischell said, the most obvious beneficiaries will be those at the highest risk of heart attacks because of their ages and medical histories. Eventually, he said, its reach might extend to lower-risk candidates, such as men in their 50s who have no heart symptoms but want to improve their odds of maintaining a healthy heart.

One of the most important functions of the Guardian will be to convince people in denial to take heart attack symptoms seriously, Fischell said. National statistics show that the average heart attack victim does not reach a hospital until three hours after chest pain begins, and that’s largely because patients – especially men – don’t acknowledge their symptoms. In 15 percent to 20 percent of all heart attacks, patients have no physical symptoms.

Fischell, 51, said the product has been developed over the past five years through the Shrewsbury, N.J., life-sciences firm Angel Medical Systems Inc., which he co-owns with his father Robert Fischell and brother David Fischell.