Clarke said: "I know I am extremely fortunate to be here.
"In the light of recent events involving footballers who have suffered heart attacks, I am the real lucky one, because I have survived.
"I remember feeling a bit lethargic on the field in the first half and I was involved in a collision with our goalkeeper Paul Henderson, which led to their goal.
"I sat quietly in a corner of the dressing room and felt a bit queasy. I can recall Patrick Kisnorbo talking to me, but it wasn't really registering. Then I just passed out.
"When I was told what had happened, the blood drained from my body. I just thought I could have been dead, and that I might never have seen my family again.
"When you think about Sevilla player Antonio Puerta, it goes without saying that a day won't pass when I don't cherish every moment in my life."