Why did my dog die

This morning at 2:00am my newfoundalnd let out a cry like he was dreaming and I awoke to get him at the bottom of our bed.. he would not wake up and breathed a few deep fast  breaths and died in my arms as I tried mouth to mouth and nothing..I am so sad right now as I have a big loss in our family.. Maximus was only 18 months old and 160lbs..He was fit and had no problems at all, the day was normal, his usual playful self....Please can someone tell me what could of happened as I am heart broken.? ..Up to date with all shots etc so we are at a loss and we can not stop crying...........

[Aleda M Cheng, D.V.M., C.V.A]

I am so very sorry for your loss!

He may have had an identified congenital problem such as heart disease and his heart may have simply given out.  Or, he could have had a bloat or gastric dilatation volvulus (GDV) in which the stomach turns on itself.

I am glad that he did not suffer.