What causes a cat's sudden death from air in the heart sac and lungs?

Acute stress does not cause pulmonary arteries to appear enlarged on x-rays. This is a change that happens over time. Enlarged pulmonary arteries can be found with heartworm infestations, a left to right shunt in the heart, pulmonary hypertension and pulmonary thromboembolism. Your vet will help to narrow-down the cause of this with further testing. I hope that helps and Kitty gets better soon.

I am very sorry to hear that. This could be either due to an acute cardiac problem or respiratory one, but it is likely that the lungs filled up with fluid. A post-mortem examination would help to shed some light on the underlying cause of it.

He may have had an injury, been hit by a car or he had a congenital heart defect that caused a blood clot at the bifurcation of the aorta (that paralyses hind legs and hurts terribly). This can also cause a clot in the lungs which would cause breathing problems. Unfortunately most cats with these blood clots die within a short time. I am so sorry for your loss. This is very sad.

My condolences on the loss of your cat. Without a post mortem exam, the cause can be difficult, if not impossible, to determine. Potential causes include cardiac conditions (including congenital defects), toxicity, infection or trauma.

Thank you for the additional information. Heart murmurs can affect the breathing in a couple of ways. One is that the murmur often times is due to a leaky valve which means the blood is flowing backwards, which then causes fluid to back up into the lungs and breathing to be more difficult. In cats, this fluid can also build up around the lungs and press in, decreasing lung volume. We hear heart murmurs because of turbulent blood flow and this turbulence increases the risk of forming blood clots, especially in cats. If these blood clots then break off, they can travel through the body and lodge somewhere. If the clot ends up in the lungs, this is called a pulmonary embolism and can cause difficulty breathing. It sounds like she's improved a bit, but if she's still gasping, it is an emergency and she needs to be seen by a veterinarian right away.

I'm so sorry you lost your cat so suddenly! An upper respiratory infection would not typically cause seizures. An upper respiratory infection can occasionally cause pneumonia or severe dehydration that could be life threatening but you would probably see other signs like trouble breathing or extreme lethargy. A heart murmur may or may not be related to underlying heart disease, but if there was heart disease present it could potentially lead to a seizure and sudden death. If he died recently you could consider taking him to your vet for a post mortem exam (autopsy) to try to determine what the cause may have been, but it can be difficult to know for certain.

Hi, I am sorry to hear that your cat suddenly passed away. Since her death was sudden and her clinical signs had resolved with treatment of chylothorax, I am also inclined to think a clot caused the sad outcome. I am sorry, it is very sad and unexpected. I have come across this before with trauma, heart failure patients and also in a dog post gastric torsion surgery. I send you all my sympathy.