One tree hill viewers, how did clay's wife Sara die?

Yes I remember that episode. It was a good one. As for how Sara died they never explained it because I watched all the episodes and I though it was weird because they never said she had a heart condition or anything like that. All of a sudden she was in the kitchen getting something out of the fridge and then she just fell to the floor. But yeah they never explained why. My guess is that she had a heart condition or something, but they still have not said exactly what is was. Sorry but I hope that helps. I am a hard core One Tree Hill fan and I would let you know if I knew.