Seizure, blood clot?

[kdbv]

HI. My 16 yrs old cocker spaniel died a couple of months ago.  I am not sure what was the cause and i need to know.
He felt and apparently broke the cruciate ligament of his hind leg.  He survived the operation and was doing fine.  The artificial ligament broke two days ago and the dr said he needed to operated again.
He did and survive the operation but the ligament broke two days later.  We decide we would build a prosthesis or something to help him walk .   On the morning he died he refused to eat or drink water but he was very affectionate.  Then he tried to stand up and i help him but he is anxious so i carried him.  He started screaming, arching his back and bitting my shirt... i put him on the bed, his eyes went backwards and he kept screaming... after we get the vet they put a lot of analgesic and he keeps screaming... he is quite for a bit then he screams again... until he died.
I dont know what happened.  Did i hurt him when i lift him? did he has a heart attack? are heart attack supposed to be that painful?  did he have a seizure? was he conscious? was he screaming of pain?
Thanks... i just need to know what happened.  The vet said he was old and probably had a heart attack... but i am not sure.

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

I am so sorry for your loss.  There are a few possibilities for the symptoms you describe.

One cause is back pain,and others are seizure or stroke.  The eyes going backwards in the head sounds like a seizure.  Older dogs can get calcifications of their spinal cord disks.  These calcifications, can break off (as cartilage emboli),  and circulate in the blood and become lodged at various locations such as spinal nerves,  and the brain.  They can then cause damage,pain and paralysis.  A piece could also theoretically end up in the brain causing a stroke.  Emboli can also travel to the heart, so heart attack is also possible.

I am certain that you did not do the damage by lifting him.

[kdbv]

HI Dr. Aleda.  Thanks for your reply.  I appreciate your help.I keep going over and over in my mind trying to realized what i did wrong.
Are seizures painful? was he screaming because the seizure? because he was in pain?

I spent 16 years making sure he was happy and the last hours i could not do anything to aleviate his suffering.  

Thanks