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Feline aortic thromboembolism
A blood clot formed in the heart breaks away and blocks the artery that supplies blood to the hindquarters. The muscles of the hind legs no longer receive blood and suddenly stop functioning. The cat, normal a few minutes earlier, collapses...
What is it?
A blood clot formed in the heart breaks away and blocks the artery that supplies blood to the hindquarters. The muscles of the hind legs no longer receive blood and suddenly stop functioning.
The cat, normal a few minutes earlier, collapses, screams and can no longer get up. This is one of the most painful situations in feline medicine and an immediate veterinary emergency.
In the vast majority of cases, heart disease was present without having been detected: the accident is often the first visible manifestation.
Key point
Vital and very painful emergency. Sudden paralysis of the hindquarters in a cat requires immediate consultation, without self-medication and without waiting for spontaneous improvement.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Brutal installation, in a few minutes, in a cat who was doing well.
The two rear legs – sometimes only one, more rarely a front leg – become unusable: the cat drags itself along the front of the body.
Intense pain: he screams, pants, refuses to be touched or moved.
The affected legs are cold; the pads and claw beds become pale or bluish.
No pulse is perceptible in the affected limb; the muscles harden within a few hours.
Rapid and difficult breathing, often with open mouth, when heart failure accompanies the episode.
Some cats vomit or are in shock, very depressed and cold.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
A disease of the heart muscle, most commonly hypertrophic cardiomyopathy, causes blood to stagnate in an enlarged chamber of the heart.
Stagnated blood coagulates and forms a clot, which grows and then breaks off.
Carried away by circulation, this clot gets stuck where the aorta divides to supply blood to the two hind legs.
Added to the mechanical blockage is the release of substances which constrict the small neighboring vessels: emergency circulation cannot be established, which explains the severity of the attack.
Other causes exist – tumor, advanced thyroid disease – but remain in the minority.
Pre-existing heart disease, known or not: this is the main factor.
A dilated left atrium on ultrasound is the most useful red flag for identifying cats at risk.
A first episode strongly exposes a second.
Males and breeds predisposed to cardiomyopathy are overrepresented.
An episode of significant stress or an intercurrent illness can precipitate the accident, without being the cause.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
It's an emergency: take the cat to a veterinarian immediately, handling it as little as possible and keeping it warm in a transport crate.
Do not give any medication from your pharmacy, in particular any human anti-inflammatory or painkiller: many are toxic to cats, even in small quantities.
Do not massage the paws or try to make the animal walk: this does not restore circulation and increases the pain.
In the office, the priority is relief of pain, which is severe, then oxygen if breathing is difficult.
The diagnosis is often obvious on examination: cold limbs, absence of pulse, contracted muscles, discolored pads.
A cardiac ultrasound is carried out as soon as the cat's condition allows it, with a blood test assessing the kidneys, potassium and the consequences of lack of oxygen on the muscles.
Treatment
The treatment is hospital-based and is based primarily on powerful painkillers: the cat's comfort comes before everything else.
Medicines that thin the blood are given to stop the clot from growing and prevent a new one from forming; the body dissolves the existing clot itself, slowly.
Attempts at emergency dissolution or surgical removal of the clot are rarely carried out: they expose one to severe complications when circulation is restored.
Associated heart failure is treated in parallel, with caution, because the needs of the two problems may conflict.
Monitoring focuses on pain, kidney function, potassium levels and the gradual recovery of mobility.
When the pain cannot be controlled or the damage is too extensive, euthanasia is a legitimate decision, to be discussed with the veterinarian. Letting suffer is never an acceptable option.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
The only real lever is the screening and monitoring of heart disease before the accident.
A cat with cardiomyopathy with a dilated left atrium can receive treatment intended to limit the formation of clots: it reduces the risk without eliminating it.
A cardiac ultrasound in breed cats at risk, or as soon as an abnormal murmur or rhythm is heard, allows the animals concerned to be identified.
Monitoring resting respiratory rate at home helps spot cardiac worsening before complications occur.
Possible complications
Damage to the kidneys and muscles deprived of blood, with the release of toxic substances into the circulation.
Dangerous rise in blood potassium as circulation is restored, potentially disrupting the heart.
Skin lesions or loss of tissue at the ends of the limbs when irrigation does not return.
Recurrence, frequent, despite well-conducted treatment.
Associated heart failure, which clearly complicates treatment.
When to see a veterinarian
Your cat can no longer use its back legs: go to the veterinarian immediately, day or night.
He screams, pants and refuses to be touched.
Its hind legs are cold, its pads pale or bluish.
He breathes with his mouth open or very quickly.
He drags a paw that suddenly appears unusable, even without a fall or accident.
Do not wait until the next day and do not give any medicine from your cabinet: every hour counts, for the pain as well as for the future of the limb.
Prognosis
The prognosis is guarded and can be judged over the first few days.
A cat in which only one paw is affected, which retains some heat in the limb and which is not in heart failure has a better chance of regaining normal walking.
Limb function returns gradually, over several weeks, when it returns.
The underlying heart disease remains and recurrences are frequent: cardiological monitoring after the attack is part of the treatment.
Frequently asked questions
My cat has lost the use of his back legs: could he have simply had a fall?
It's possible, but affecting both paws at the same time, with intense pain, pale pads and cold paws, points to a clot. In all cases, sudden paralysis is seen in an emergency.
Can I give him some painkiller while I wait?
No. Common human painkillers are dangerous, sometimes fatal, for cats. The only useful action is to transport it in a quiet, warm place, without handling it more than necessary.
Will my cat regain the use of its paws?
Some cats walk again after several weeks, others not. Recovery depends on the number of limbs affected, the remaining circulation and the condition of the heart. The veterinarian re-evaluates regularly during the first few days.
Can this happen again?
Yes, the risk of recurrence is real, because the heart disease that caused the clot persists. Long-term fluidifying treatment and cardiological monitoring reduce this risk without eliminating it.
References
AAFP — American Association of Feline Practitioners
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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