Caval Syndrome

• Cause:retrograde migration of adult heartworms from the pulmonary artery into the right ventricle, right atrium and vena cava.
• Signs:acute onset weakness, lethargy, inappetence, respiratory distress and commonly hemoglobinuria.
• Diagnosis:echocardiography, thoracic radiographs, electrocardiography.
• Treatment:surgical removal of the obstructive mass of heartworms.
• Prognosis:guarded to poor, even with surgical removal reported mortality ranges from 14% to 42%.

Acute presentation

• Weakness.
• Lethargy.
• Inappetence.
• Hemoglobinuria Hemoglobinuria.
• Pale mucous membranes.
• Prolonged capillary refill time.
• Weak femoral pulses.
• Jugular venous distension and pulsations.
• Hepatomegaly Abdominal organomegaly.
• Ascites.
• Frequently a right-sided heart murmur is auscultated that may increase in intensity with the onset of caval syndrome.
• A split 2nd heart sound may be associated with pulmonary hypertension Pulmonary Arterial Hypertension (PHT).

Geographic incidence

• Temperate and tropical areas where mosquito hosts are endemic. 16%-20% of dogs with heartworm disease Canine cardiopulmonary dirofilariasis in the US are reported to developed caval syndrome.
• Requires high density of mosquitoes to produce significant transmission.

Age predisposition

• Mean onset 5 years of age.
• Range 1.5-10 years.

Cost considerations

• Surgical removal of worms with appropriate supportive care is costly.
• Adulticide therapy Milbemycin oxime Ivermectin Selamectin Moxidectin Melarsomine is required 2 to 3 weeks following surgical removal of heartworms followed by heartworm prophylaxis.