State health officials investigating claims that a Towson cardiologist performed hundreds of unnecessary medical procedures have identified other doctors in Maryland with similarly questionable practices, The Baltimore Sun has learned.

Several cardiologists in the state have performed a suspiciously high number of the same invasive cardiac stent procedures that Dr. Mark G. Midei is accused of over-performing at St. Joseph Medical Center, according to an analysis of data from the state's Health Services Cost Review Commission.

The discovery was made as part of a broader statewide investigation of hospitals that was triggered by the allegations at St. Joseph, and is raising concerns that the accusations against Midei might not be isolated.

Investigators plan to review the work of the other cardiologists — who were not identified to The Baltimore Sun — going back five years. Sources also said they expect the investigation to eventually expand to include inquiries into other medical specialties and procedures.

Del. Peter A. Hammen, who asked the state agencies to investigate, cautioned against jumping to conclusions about what the higher rates of stent placement indicate.

"Once we have [all] the numbers in front of us, we'll be able to make, obviously, better sense as to what they mean and what actions we should take," said Hammen, who was briefed on the initial data. "It's early in the state's investigation."

State investigators, after interviewing medical specialists and analyzing billing data reported by hospitals, have determined that doctors who perform a diagnostic test called a cardiac catheterization typically find blockage requiring treatment with a stent about 30 percent of the time.

But Hammen and other sources say the regulatory data suggests Midei performed stent procedures nearly twice as often, and that other Maryland doctors are high enough above the 30 percent benchmark to warrant a closer look.

Still, a spokeswoman for the American College of Cardiology said there was no reason for stent patients to panic. The devices, which can't be removed, are relatively safe once they're implanted. She suggested that people with questions or concerns about the validity of their own stent placement either talk to their doctors, or to an outside physician.

Arthur Caplan, chairman of the Department of Medical Ethics within the University of Pennsylvania, said differences in the rate of procedures can be caused by a variety of benign reasons, including variations in medical training and the types of patients being seen.

But wide differences demand investigation, he said.

"There are the occasional outliers that are so far out that red flags should be going off," Caplan said, adding that "for most of the things that are overused, there is an amazing relationship to profit."

Stents, which are designed to prop open arteries and improve blood flow around the heart, are a multimillion-dollar industry, bringing in $222 million in business to Maryland hospitals during the past fiscal year alone. They're relatively simple to insert and bring in $10,000 or more per procedure.

And patients often prefer them as an alternative to heart surgery. Stents can offer quick relief from symptoms like chest pain, though recipients often have to take blood-thinning drugs for life.

Clinical guidelines generally suggest that an artery be at least 70 percent blocked before a stent is placed, and St. Joseph's rules consider anything less than 50 percent blockage to be "insignificant." But court documents allege that some of Midei's patients were told they had blockages in the 90 percent range, while a subsequent review of their records shows blockages closer to 10 percent or less.

Midei left St. Joseph last year amid accusations that he falsified records to make it appear that patients needed stents when they did not. St. Joseph reviewed Midei's records over a two-year period and identified 585 people who may have received unneeded stents from the well-regarded cardiologist. Hospital officials, who recently concluded their investigation, said they were tipped off by a patient complaint in April 2009.

Since then, local malpractice attorneys say they have been approached by hundreds of Midei's patients, and a handful of lawsuits against him and St. Joseph have been filed.

In a statement e-mailed to The Sun Friday, St. Joseph officials said the hospital "is a cardiac referral center and frequently receives more complicated cases from referring physicians and other hospitals, so the hospital's volume would be higher than some other hospitals. However, St. Joseph has acknowledged that Dr. Midei appears to have performed stent procedures that may have been medically unnecessary."

After that finding, the hospital withdrew Midei's practice privileges at the hospital and implemented "an enhanced state-of-the-art peer review process" for its cardiac catheterization lab. The hospital has said it reviewed the records of other St. Joseph cardiologists, as well, but found no problems.