[KimberlySRN]

That does make sense. But Suri ran into a wall, no sound, no kicking, nothing but a heart beat. I think her head snapped to the side, and her heart was beating because of the adrenaline of running around.

Originally Posted by Wylie's Mom

Both of these make me wonder about a Pulmonary Embolism. It does kind of fit -- I just don't know how common this is in dogs. It can result in very sudden death.

Here is a basic overview: Pulmonary embolism - Wikipedia, the free encyclopedia