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Writer/director Kevin Smith has survived a "massive heart attack".

The Clerks filmmaker was due to perform two of his Kevin Smith Live! stand up shows at the Alex Theater in Glendale, California on Sunday evening, but cancelled the second event due to illness.

Taking to Twitter on Monday morning, Kevin explained that instead of taking to the stage, he rushed to hospital and had undergone emergency surgery.

"After the first show this evening, I had a massive heart attack," he wrote alongside a selfie showing him in his hospital bed. "The Doctor who saved my life told me I had 100 per cent blockage of my LAD artery (aka 'the Widow-Maker'). If I hadn't canceled show 2 to go to the hospital, I would've died tonight. But for now, I'm still above ground!"

The left anterior descending artery (LAD) runs down the front of the heart and supplies the front and main wall of the organ.

Interventional cardiologist Dr. Mustafa Ahmed previously described the Widow-Maker heart attack by explaining: "No one knows exactly who came up with the term, but the reason they did is likely that if that artery is blocked right at the beginning of its course, then the whole artery after it goes down. This essentially means that the whole front wall of the heart goes down. As far as heart attacks go, this is a big one."

Kevin, 47, hit headlines in 2015, when he revealed that he had shed an incredible 85 pounds after being warned that his excess weight could lead to health problems.

Speaking to Men's Health magazine about how he had lost the weight, Kevin explained that he had cut out sugar and started drinking green juices, as well as introducing some gentle exercise into his daily regimen.

"My 'working out' is I've got this hill outside my house – like, right outside my house, you walk out the door and – boom!" Kevin told the publication. "You're on this hill, so I'll take my dogs out and see who starts breathing heavy and sweating first. I don't really exercise. I'm not a 'fifty reps' kind of guy. I just walk every day."