Jody McDonald, the midday host on sports talk WPEN (950), is scheduled to undergo unspecified heart surgery Monday, a station source said today. "Jody Mac," who was last on the air Tuesday, had been scheduled to be on vacation next week but began complaining of discomfort recently, the source said.

McDonald, who is in his mid-40s, joined the station when it went to sports in October 2005. He previously worked for ESPN and sports talkers WFAN in New York and now-rival WIP in Philadelphia.

Station management would not talk about McDonald or his condition. A call to McDonald was not returned.

Michael Bradley has been substituting for McDonald.

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