A very tragic weekend

We're still in shock and very depressed after this past weekend. We were at a sheepdog trial in NY north of NYC near the CT line. Sunday morning my wife was "setting sheep" (bringing out and keeping sheep in place for the competing teams) with her dog Bette (11 years). After completing her stint setting sheep she put Bette in her crate to reset. Bette went in alert and relaxed. About an hour later we went to take the dogs out for lunch time potty break and Bette was unable to stand, she was mentally alert. There were 5 vets at this trial and one is certified in Chiro; she checked Bette over and could find no physical cause for the lack of muscle control in her back legs (she did have feeling in her back legs). While checking Bette over she started to loose color (grey gums). We contacted 3 more vets that were at the competition and the 4 of them worked to try to save Bette (IVs, Ultrasound to investigate, CPR, epinephrine, etc.) but within about an hour of getting her out of her crate she was dead. Bette was tested for the cause of death and the preliminary results indicated vegetative endocarditis (bacterial growth on a heart valve); bits of this growth likely broke off leading to embolism(s). Bette had no symptoms of endocarditis (we looked up the symptoms) prior to this; she was an athletically fit Border Collie. My wife is devastated.