‘I’m back:’ Arnold Schwarzenegger gives update after heart surgery

"It's true: I'm back," Schwarzenegger posted on Twitter Monday. "I went to sleep expecting to wake up with a small incision and woke up with a big one - but guess what? I woke up, and that's something to be thankful for. Thank you to the doctors & nurses. And I'm truly filled with gratitude for all of the kind messages."

An initial report from TMZ said the 70-year-old actor underwent emergency open heart surgery after complications emerged from a less-invasive catheter valve replacement procedure. Schwarzenegger's spokesman Daniel Ketchell issued a statement confirming the surgery Friday afternoon.

Related: Arnold Schwarzenegger undergoes open heart surgery, rep confirms

"Yesterday, Governor Schwarzenegger underwent a planned procedure at Cedars-Sinai to replace a pulmonic valve that was originally replaced due to a congenital heart defect in 1997," Kitchell said in the Friday statement. "That 1997 replacement valve was never meant to be permanent, and has outlived its life expectancy, so he chose to replace it yesterday though a less-invasive catheter valve replacement. During that procedure, an open-heart surgery team was prepared, as the frequently are in these circumstances, in case the catheter procedure was unable to be performed. Governor Schwarzenegger's pulmonic valve was successfully replaced and he is currently recovering and is in stable condition."

On Sunday, Ketchell said Schwarzenegger "had a planned catheter surgery that used the backup plan of open heart surgery to successfully replace the valve."

Related: PHOTOS: Arnold Schwarzenegger through the years

Ketchell said that when Schwarzenegger woke from surgery, his first words were a nod to his “Terminator” catchphrase.

"His first words were actually 'I'm back,' so he is in good spirits," Ketchell said Friday.