More than 200 heart patients at Harlem Hospital Center died after undergoing heart tests that were never read by doctors, according to a hospital employee briefed on Friday on an investigation into the handling of 4,000 tests in the past three years. The president of the city's Health and Hospitals Corp., which runs Harlem Hospital, said it would be premature to link any deaths to the failure of doctors to read the heart tests. But investigators are trying to determine whether one patient, a woman who died soon after having the test, an echocardiogram, might have survived had her test been properly handled, according to the employee who was briefed. He and other employees at the hospital spoke on the condition of anonymity because they had been ordered not to discuss the situation. The disclosure of the deaths came as several Harlem Hospital doctors said they had known about the backlog of 4,000 echocardiograms since 2007 but were helpless to do anything about it. They said they were chronically understaffed and had been rebuffed when they proposed to hospital administrators that more people be hired. No information was available Friday on the causes of the more than 200 deaths. Empire BlueCross BlueShield, one of the nation's largest insurance companies, said Friday that it was beginning an investigation into whether patients it insured had been improperly treated or had been billed for uncompleted heart tests. The state's Medicaid inspector general's office indicated it was watching the case closely because of the possibility that money had been wasted. Alan Aviles, the president of the hospitals corporation, disclosed on Tuesday that 4,000 echocardiograms performed at Harlem Hospital from 2007 to 2010 had been read by technicians and not by cardiologists. He said that Columbia University, which provides doctors to the hospital, had discovered in a routine review of hospital operations the previous Thursday that the tests had not been read by doctors, as required. One administrator has since been fired, and another demoted. On Friday, Aviles would not confirm the report of 200 deaths or release the number of deaths among the 4,000 patients, saying that the corporation was still investigating. The hospitals corporation and Columbia have begun to go back over the 4,000 tests and have cardiologists read them to see what was missed. The Harlem Hospital doctors said the hospital had six attending cardiologists and six fellows in 1999. It is now down to three full-time cardiologists, and the fellowship program has been discontinued, they said. Hospital corporation officials said that counting part-timers, Harlem Hospital had the equivalent of five full-time cardiologists. 