Max George typed out his will on his phone before having a pacemaker fitted.
The 36-year-old pop star underwent emergency surgery in December, and Max has now revealed that he genuinely feared for his life.
Speaking to The Sun on Sunday newspaper, Max recalled: "I hadn’t been feeling myself for a few days, I started feeling a bit rough.
"I couldn’t put my finger on it. I was quite lethargic and stuff, struggling to get out of bed. But I didn’t think it was anything serious.
"Luckily I’d gone around to my mum’s to stay and I woke up and I remember looking at my hands and they were blue, and my arms were a grey colour and I was freezing cold. I struggled to even sit up in bed."
Max subsequently checked his blood pressure and found that it was "pretty low".
The singer - who is best known for starring in The Wanted - shared: "As I did that my mum came through the door and she gasped. She said, ‘What’s wrong? You’re blue. I need to ring the doctor now.’"
Max was later rushed to hospital, where he was informed that he needed to undergo an emergency operation, after being diagnosed with an atrioventricular block.
At one stage, Max feared he might not survive the operation - but he was ultimately able to return home on December 23.
Max recalled: "That first night I wrote a will, I thought I was going to die.
"If I could go from being absolutely on top of the world to being told ‘the bottom part of your heart isn’t working’, I kept thinking in my head, ‘Well, what if the top half stops working overnight?’"
