The 28-year-old Australian was just 10 games into his three-year contract with the Bulls when he suffered a heart attack on the way home from the Magic Weekend fixture with Leeds in Manchester last May.
But Purtell, who last month became an ambassador for Heart Research UK, came through a series of tests and, after returning for pre-season training in November, was cleared by a London specialist to resume his career on Wednesday. The Australian said: "I've got these next two seasons to play and I look forward to the rest of my contract."
Resuming his Super League career was the last thing on his mind as he lay in a Leeds hospital bed amid wondering if he would be able to lead a normal life again.
He said: "Did I think I wouldn't play again? At the start that was probably all I was thinking.
"I didn't know too much about it and the advice from the first doctor was that it was probably going to be a hard road to come back from.
"When I saw the specialist down in London (in November) and he said there might be a chance I could play again, I didn't take too much convincing that I wanted to try and get back to playing.
"I've enjoyed the move over here and I would have been disappointed had this adventure come to an end."
Purtell has come off the blood-thinning medicine and will now step up full contact training.
Unable to make his comeback with partner club Dewsbury because of visa restrictions, the former Canberra and Penrith threequarter will go straight into Super League action and could even come into contention for a place in Sunday's home game against Hull KR.