The case, being investigated by the Arizona Medical Board and other agencies, has startled doctors and authorities in Arizona and beyond and shed light on the gray areas between federal and state laws that regulate medical devices and the doctors who use them.

Advanced Cardiac Specialists, a private practice with offices and labs across the Phoenix area, obtained the pacemaker off eBay, an online auction site. It had been stolen from a hospital in Sacramento. An arrest has been made in the theft.

While authorities continue to investigate the situation, experts say the case raises ethical questions.

No federal or Arizona laws directly regulate from whom medical practitioners can buy the products they use, even devices as sensitive as pacemakers.

On a search of more than 17,000 health-care items available on eBay, The Republic found silicone breast implants, dialysis machines, used pacemakers and external defibrillators. Experts say some items, especially those that could be implanted in the body, present serious safety concerns regarding sterility and performance if obtained from an unusual source.

"It raises enormous ethical issues," said Arthur Caplan, director of the Center for Bioethics at the University of Pennsylvania. "You can't go out and buy supplies from unknown vendors and put patients at risk. You have no quality control. It is unconscionable."

According to police records, Advanced Cardiac Specialists' purchasing manager, Greg Etts, bought two pacemakers off eBay in November from a woman who claimed to own a medical-supply shop. The company paid $411.99 for both. The pacemakers are worth as much as $6,000 each. Police confiscated the second pacemaker.

Pacemaker manufacturer Medtronic says it sells its products only directly to hospitals or clinics. But Advanced Cardiac Specialists' attorneys say hospitals or clinics sometimes exchange products, especially if the device is near expiration. Because of the low price, the company took the risk that it might have to discard the pacemaker if it was expired. Advanced Cardiac Specialists had never purchased pacemakers off eBay or similar sites before, and it was able to ensure the safety of the pacemaker by inspecting the tamperproof packaging and testing the device, officials said.

"There was nothing unethical about this purchase," attorneys Barry Mitchell and Bob Milligan wrote in responding to questions from The Republic.

But other hospital officials and cardiologists said that they were shocked by the purchase and that their facilities follow strict, internal guidelines about where they buy products such as pacemakers.

Dr. Ted Diethrich, medical director of the Arizona Heart Institute and Hospital, said the decision to purchase something like this on eBay "has to be about profit" and could put patients at risk.

"Is this the device you think it is? Is it a possible reject?" Diethrich asked. "You open yourself to all kinds of questions, and the last thing you want to do is give that medication or implant that device when you have no assurances of the background of the product."

The Food and Drug Administration, which is reviewing the case, is charged with approving medical devices and regulating their manufacture. Although it restricts who can buy some devices, such as pacemakers, there are no federal rules that restrict where or from whom doctors or hospitals can obtain the devices, FDA officials said. The FDA does require manufacturers to record where the devices end up so that patients can be aware of recalls.

Officials say they have worked with eBay to make sure products sold on the site bear the right FDA notices and are not illegal to sell.

The auction site itself does not review every listing and does not confirm the quality of the products or the source, an eBay spokesman said.

"The Internet has posed a lot of new opportunities and new challenges as far as people getting access to new medical technologies," said Brad Stone, an FDA spokesman. "The idea that someone might purchase an implantable device is not something that would come to mind when people thought of the Internet."

State laws also do not address the issue. The Arizona Board of Pharmacy's executive director said it is unclear whether his agency could have any authority over medical devices. The Department of Health Services, which licenses facilities like the Advanced Cardiac Specialists clinics, said it investigated but found no violation of its rules. The Arizona Medical Board is investigating Dr. Ashok Garg, the surgeon who implanted the pacemaker. It has no authority to look at the company or its non-physician employees.

"We would have to prove the individual doctor being investigated violated a rule or law," said Timothy C. Miller, the board's executive director. At a hearing last month, the board considered a staff recommendation to restrict Garg's ability to perform surgical procedures and decided there was not enough evidence to do so.

Some experts, such as Caplan, recommend that patients discuss all aspects of their treatment with their doctor, including asking how any products used were obtained. Caplan said no new laws are needed and that the industry will check itself.

But some patients say the situation is troubling, and they wish there were rules to keep this from happening again.

"How do you know if it has been used or tainted with something?" asked Donna Chandler, 71, of Casa Grande.

Her husband, Eldo, had a pacemaker implanted by another Advanced Cardiac Specialists physician last year. "Everything else is regulated. It seems like not just pacemakers but other health items should have some safety guidelines."