Former All Blacks superstar Sonny Bill Williams gets open heart surgery

Williams, who won two Rugby World Cup titles in 2011 and 2015, said a serious heart defect, which he had been born with, was discovered during a follow-up appointment following neck surgery.

Earlier this year, he had his fourth major neck operation and he said if his heart defect had not been detected, it could have had dire consequences.

"So, if I didn't go in and get it checked, they wouldn't know. And it's a case of a perfectly healthy-looking person, dropping dead," he explained during the video which he made with his wife titled 'My Heart Stopped'.

Williams made 58 Test appearances for the All Blacks between 2010 and 2019 and also had successful stints as a rugby league player and in professional boxing.

The 41-year-old father of five, who is a devout Muslim, was joined in the video by his wife, Alana.

"I just said bye to my husband. It's a little bit daunting, but he's so strong. He'll be ok," she said.

Williams' heart operation at Royal Melbourne Hospital was a success and he admitted that it was the most difficult experience of his life.

"It's the hardest thing I've ever done. Day two, honestly, I thought I wasn't going to make it. It was crazy," he said.

"I'm so grateful. The doctor I've seen this morning, he's just told me that having this heart implication throughout my life would have implicated me and my sporting career. And upon reflecting, I feel like towards my late-20s, I definitely felt like I couldn't get as fit as I used toâ¦

"The doctors both said that it's a miracle that you found it because it's a case of a perfectly fit looking person dropping dead. Because my heart was 7.5 centimetres, it was about to pop as the doctors said. Alhamdulillah (Praise be to God).

"And now, the doctors said that I've got a better heart than when I walked in here because it's more efficient now. The magnitude of the surgery, two open-heart surgeries in one, and it's been so successful."

He also revealed that he had hallucinations after going under the knife.

"That's when I honestly felt like I didn't know if I was going to make it," said Williams, who made 58 Test appearances for the All Blacks and who also represented New Zealand's sevens team at the 2016 Olympic Games in Rio de Janeiro.

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