Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Pulmonary edema is fluid in the lungs, and in cats it’s most often caused by congestive heart failure from heart disease such as hypertrophic cardiomyopathy (HCM). Signs include fast or labored breathing, breathing with the mouth open, and hiding or lethargy. Cats rarely cough from heart failure. Any cat breathing with its mouth open or struggling to breathe needs an emergency vet immediately. Keep your cat calm and don’t try to handle it more than necessary on the way.
Signs
- Fast breathing at rest or while sleeping
- Breathing with visible effort, with the belly moving a lot
- Open-mouth breathing or panting (never normal in cats at rest)
- Sitting hunched with elbows out and neck extended
- Hiding, lethargy, or not eating
- Blue or gray gums (emergency)
Causes
Heart-related (cardiogenic)
- Hypertrophic cardiomyopathy (the most common heart disease in cats)
- Other cardiomyopathies
- Heart disease made worse by fluids, stress, anesthesia, or steroid medication (especially long-acting steroid injections)
- Untreated hyperthyroidism or high blood pressure
Other causes (non-cardiogenic)
- Airway obstruction or choking
- Electric shock (such as chewing a cord)
- Head trauma or prolonged seizures
- Near-drowning or smoke inhalation
- Severe infection or inflammation
Getting your cat to the vet
- Stay calm and handle your cat gently, placing it in a carrier with minimal restraint.
- Keep the carrier cool and well ventilated.
- Call ahead so the clinic can have oxygen ready.
How vets treat it
- Oxygen and very gentle handling to avoid stress
- Diuretics such as furosemide to remove fluid
- Draining fluid around the lungs (pleural effusion), which often occurs alongside edema in cats
- Diagnostics once stable: chest X-rays, a heart ultrasound, blood pressure, and bloodwork
Long-term care for heart failure
- Diuretics, adjusted to the lowest effective dose
- Clopidogrel to reduce the risk of blood clots, which can cause sudden back-leg paralysis
- Other heart medications as your vet or a veterinary cardiologist recommends
- Treating hyperthyroidism or high blood pressure if present
- Regular rechecks of kidney values and electrolytes
Home monitoring: count sleeping breaths
Count your cat’s breaths for 30 seconds while it’s asleep and relaxed, then double it. Your vet will give you a target, and many advise calling if the sleeping breathing rate is consistently above about 30 breaths per minute. Rising rates can signal heart failure days before a crisis.
Also call immediately for
- Sudden back-leg weakness or paralysis, cold back legs, or crying in pain (possible blood clot)
- Open-mouth breathing, collapse, or fainting
What to avoid
- Human medications, including aspirin, unless prescribed.
- Stopping diuretics or other heart medications without your vet.
- Stressful handling and travel when your cat is breathing hard.
- Salty treats and human foods.
Frequently asked questions
Can a cat recover from pulmonary edema?
Yes. Many cats recover from a first episode with prompt treatment. Those with heart disease need lifelong medication and monitoring.
Why didn’t my cat cough?
Unlike dogs, cats with heart failure rarely cough. Fast breathing is the main sign.
Can heart disease in cats be detected early?
Sometimes. A heart murmur, abnormal rhythm, or blood test (NT-proBNP) can prompt a heart ultrasound, but some cats show no warning signs.
Sources
- Luis Fuentes V, et al. ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats. J Vet Intern Med. 2020
- Hogan DF, et al. Secondary prevention of cardiogenic arterial thromboembolism in the cat: the double-blind, randomized, positive-controlled feline arterial thromboembolism; clopidogrel vs. aspirin trial (FAT CAT). J Vet Cardiol. 2015
- Merck Veterinary Manual: Congestive heart failure in cats
- Ployngam T, et al. Hemodynamic effects of methylprednisolone acetate administration in cats. Am J Vet Res. 2006
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.