The federal agency responsible for investigating Medicare fraud and other health law violations, and whose probe of Towson, MD-based St. Joseph Medical Center led to a leadership shake-up last month, has ordered a group of cardiology specialists affiliated with the hospital to hand over business records. Midatlantic Cardiovascular Associates, a dominant cardiology practice at hospitals in the Baltimore area, received a subpoena from the Department of Health and Human Services in June—the month the agency made a similar demand of St. Joseph, documents show.