Caval Syndrome in Cats: Causes, Symptoms & Treatment

Caval syndrome in cats is a rare but severe complication of heartworm disease caused by the parasitic worm Dirofilaria immitis. It happens when a large mass of mature heartworms obstructs blood flow within the right side of a cat's heart, particularly around the tricuspid valve. This blockage can cause life-threatening cardiovascular complications and requires urgent veterinary treatment.

The Causes of Caval Syndrome in Cats

The condition arises due to heartworm infection, which though less common in cats than dogs, can still lead to serious disease. Heartworms develop inside the cat’s heart and lungs, but when there is an overload of worms, a mass may dislodge and enter the right ventricle. Here, the worms become entwined around the tricuspid valve apparatus, preventing it from closing properly.

This interference causes tricuspid regurgitation, where blood flows backwards into the right atrium as the right ventricle contracts. This backward flow disrupts normal circulation and can severely compromise cardiac function. It also causes haemolysis, the destruction of red blood cells, contributing to anaemia and other complications. The liver may also be affected due to congestion, sometimes leading veterinarians to describe this condition as "liver failure syndrome".

Recognising the Symptoms

Cats suffering from caval syndrome typically show acute, severe symptoms that differ from typical heartworm signs. Key symptoms to watch for include:

• Jaundice (yellowing) of the eyes and skin
• Blood in the urine (haematuria)
• Pale gums and mucous membranes indicating anaemia
• Weak or low femoral pulse pressure
• Elevated liver enzymes found in blood tests
• Heart murmurs detected by a vet
• Collapse or weakness due to circulatory shock

Additional signs may include respiratory distress, fluid accumulation in the chest or abdomen (pleural effusion or ascites), and lethargy. Because these symptoms are sudden and severe, immediate veterinary attention is critical.

Diagnosing Caval Syndrome

Accurate diagnosis involves a thorough veterinary history and clinical examination, with a focus on cardiovascular evaluation. The primary diagnostic tool is echocardiography (ultrasound of the heart), which can visualise heartworms blocking the right heart chambers and assess valve function. Other tests include blood work to detect anaemia, liver function abnormalities, and possible heartworm antigen tests.

Treatment and Care

Caval syndrome in cats is a medical emergency requiring quick, specialised intervention. Unlike dogs, cats tolerate heartworm medications poorly, so surgical removal of the heartworms is often necessary. The procedure involves general anaesthesia and careful extraction of worms from the right heart via the jugular vein.

Post-operative care is intensive and critical. Cats require hospitalisation for monitoring and supportive treatments including fluid therapy to support heart function. Veterinarians typically prescribe corticosteroids to reduce inflammation and antibiotics if infection is a concern. Supportive care aims to stabilise the cat’s condition and address complications like anaemia and liver dysfunction.

Prognosis for Cats with Caval Syndrome

The prognosis is guarded due to the severity of the condition and risks related to surgery and heart failure. Without treatment, the condition often leads to rapid deterioration and death. However, prompt surgical intervention performed by experienced veterinary specialists can improve survival chances. Unfortunately, even after surgery, some cats may suffer from organ failure or recurrence of symptoms, and ongoing veterinary care may be necessary.

Summary

Caval syndrome is a rare but life-threatening result of heartworm disease in cats. It involves heartworms obstructing blood flow in the right heart, causing cardiovascular collapse. Symptoms such as jaundice, haematuria, pale gums, and collapse indicate urgent veterinary assessment is needed. Diagnosis relies heavily on echocardiography, and treatment usually requires surgical removal of the worms with intensive supportive care.

Awareness and prevention of heartworm infection, including avoiding mosquito exposure and regular vet check-ups, are essential to reduce risk. If you are considering getting a cat or already have one, understanding this severe condition can help you recognise emergency signs and seek immediate help.

Although kittens are typically less susceptible to heartworm infection, protecting your cat throughout life with preventative veterinary advice is crucial for responsible ownership.