Los Angeles ? Shares of Tenet Healthcare Corp. plunged more than 41 percent Friday after the nation’s second-largest hospital chain announced the departure of two top executives and said it would review its prices.

The announcement came in response to the federal government’s investigation of whether the Santa Barbara, Calif.-based company overbilled Medicare. The management shuffle was announced Thursday before a company conference call.

Thomas Mackey, 54, chief operating officer since 1999, retired. David Dennis, 53, Tenet’s chief financial officer since 2000, resigned.

Jeffrey Barbakow, Tenet’s chairman and chief executive, acknowledged to investors in the conference call that the company’s “aggressive” pricing policy resulted in a higher-than-average number of special payments for costly procedures, such as heart surgeries.

He denied that Mackey and Dennis were forced to resign in response to the federal audit.