The former England skipper was very distressed and has been praying with wife Victoria in a chapel at the Chest Hospital in Bethnal Green, where Ted, 59, is recovering.
A close pal has revealed that when David reached the hospital, he knelt at his father's bedside and blamed himself for his fatal condition.
"I'm sorry. This is my fault," News Of the World quoted him, as saying.
"David feels he is somehow to blame for Ted's heart attack-even though it's nobody's fault. He's drifted away from Ted over the years, but he still loves his dad desperately. It just shows you how much he loves his dad, despite their ups and downs," the pal said.
An ambulance crew en route to hospital resuscitated Ted, and later he underwent immediate surgery at the hospital.
David's wife Victoria Beckham was also present to support her husband in his difficult condition.
"She's been a rock for David. She keeps telling him, 'Don't blame yourself for this, stop having a guilt tripóit's not your fault,'" a friend said.
Victoria had cut short her million-dollar perfume launch trip to Japan to fly back to be at David's side in his hour of need.
David and his wife have taken solace in religion in order to pray for their father.
Both of them spend lot of time in the prayer room, an insider revealed.
Three days after suffering a life-threatening heart attack, Ted's condition has been described "stable" as he regained consciousness and began talking from his bed.