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Cheney's heart woes parallel advances in technology

MINNEAPOLIS, Minnesota (CNN) -- Vice President Dick Cheney's heart is benefiting from years of technological tinkering with cardiac devices.

In the nearly quarter of a century since Cheney, 60, had his first of four heart attacks, the technology of implantable devices to kick-start ailing hearts has made great strides, doctors and developers say.

Though the first clinical trial of an implantable defibrillator was carried out in 1980, it was not until 1985 -- three years before Cheney's quadruple bypass surgery -- that one became commercially available, said Bob Hanvik, spokesman for Medtronic, the Minneapolis-based maker of implant devices with about 50 percent of the market.

This year, nearly 80,000 of the devices will be implanted worldwide, about 60,000 of them in the United States, Hanvik said.

CNN's Rea Blakey explains the electrophysiology test that U.S. Vice President Cheney underwent (June 29)

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U.S. Vice President Cheney talks to reporters about his heart condition (June 29)

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The GEM III DR implanted Saturday into Cheney cost about $20,000, Hanvik said. A Medtronic technical adviser was in the operating room during the procedure, a common occurrence, he added. The company was told about the planned operation Friday, he said.

The model implanted into the vice president was approved by the U.S. Food and Drug Administration in December.

Its lithium battery -- similar to the battery disks that power watches -- has an average life of six to eight years, after which the patient will require another operation to replace it.

The device contains a warning beeper that alerts the patient when the battery is running low, or when the leads have detached from heart muscle, a rare occurrence, according to Dr. Jonathan Langberg, a cardiologist at Emory University in Atlanta, Georgia.

The device also records when a shock is delivered and how the heart was beating during the event. That information can be critical to cardiologists, who retrieve it by waving a wand over the patient's chest, which "interrogates" the device and downloads the data to a computer.

"It's like having a paramedic in your chest on standby 24 hours a day," Langberg said. Most patients who have the devices have no restrictions on their activity, he added. "These devices, once they heal in place, are not particularly noticeable or cumbersome," he said.

The GEM III DR does three things: Its pacing speeds a slow heartbeat, and its cardioversion function slows a moderately fast heartbeat. The defibrillation function also shocks hearts that are so out of synchrony they cannot pump blood efficiently, a potentially life-threatening condition.

Patients usually cannot feel either of the first two interventions. But the last one packs a wallop.

Defibrillation can be literally shocking as the device jolts the heart with 30 joules of electricity. "Patients will describe that it feels like someone has punched them in the chest," Hanvik said. "They can feel it pretty significantly."

Though the technology has advanced, screwups -- referred to as "improper delivery of therapy" -- still occur, Langberg said, primarily when a patient's heart rate speeds as a result of exercise, or when the leads detach from the heart muscle.

About 1 percent of people who get the devices die during the operation, he said.

Still, the devices save lives, Langberg said.

The technology is underused, according to the American College of Cardiology.

People with a personal or family history of heart disease are candidates for the devices, about 160,000 people per year, Hanvik said.

In Cheney's device, one lead is attached to one of his heart's two upper chambers, called the atria, and another is attached to one of his heart's two lower chambers, called ventricles, which control how much blood is pumped.

Much of the technology surrounding implantable defibrillators paralleled the technology of pacemakers -- intended solely to speed slow heart rates.

In the late 1940s, the first pacemakers were the size of transistor radios. They were powered by standard-size batteries and were worn around the neck, connected to the heart via wires that went through the skin.

But infection, a common problem at the entry site, led to the first self-contained unit in 1957.

• American Heart Association National Center
• MEDLINEplus: Heart Attack
• Medtronic

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