To entertain heart problems as a cause of systemic hypotension you are in effect saying left heart failure severe enough that the heart can’t provide enough pumping to maintain systemic perfusion. This is actually rare in dogs. Many are in backward failure (pulmonary oedema) but not in forward failure. Most dogs in heart failure from valvular disease or DCM still have OK perfusion. Only the very worst are hypotensive. Cats, on the other hand, can be horribly hypotensive when they are in heart failure.This animal looks like he could be in heart failure... Is it a dog or a cat? What do you think might be going on?