The Terminator star, 70, is understood to be in a stable condition after the unplanned operation, after complications developed during a relatively routine catheter valve replacement.
Mr Schwarzenegger went under the knife at the famous Cedars-Sinai hospital in Los Angeles after doctors determined that the emergency open-heart surgery was needed, remaining in theatre for several hours.
TMZ reported that the ex-bodybuilder was now recovering from the operation, his second on his heart.
Mr Schwarzenegger, famous for his roles in the Terminator franchise, as well as turns as Conan the Barbarian and in comedies like Kindergarten Cop, has teased a return to politics in recent weeks.
He spoke to CNN about the state of the Republican Party, after establishing himself as an outspoken critic of President Donald Trump, who he replaced as the host of the Celebrity Apprentice.