One of the largest insurance companies in Pennsylvania has fired its chief executive officer a week after he was arrested following a fight with the husband of an employee with whom he was having an affair.

Pittsburgh-based Highmark Inc. announced yesterday that the board of directors had dismissed 58 year old Kenneth Melani who had been placed on unpaid leave March 29 after he was charged with simple assault and defiant trespass.

“The board has reviewed this situation thoroughly and has taken decisive action to address the matter,” Highmark Board Chairman Robert Baum said.

Baum will serve as acting CEO.

“Our mission of providing quality, affordable health care has never been more important, and I’m looking forward to working with our employees and senior management team in addressing the many challenges and opportunities that lie ahead,” Baum said.

Baum said the board is moving forward to identify a long-term successor to the CEO position.

Moody’s Investors Services last week downgraded its outlook on the company’s credit rating, citing additional uncertainty as Highmark tries to extend its contract with UPMC so Highmark customers continue to have access to UPMC doctors and facilities without paying much higher out-of-network costs.  Highmark is also seeking approval to take over West Penn Allegheny Health System.