The low number and slow maturation of adult worms in clinical infections and the clinical signs associated with immature worms make it prudent to consider a positive antigen test diagnostic but not to rule out heartworms based on a negative antigen test. Most cats with heartworm disease are antigen negative. There are now several different assays for antigen in the blood, and each should be reviewed for strengths and weaknesses. However, currently the antigen tests appear to be detecting the same basic glycoprotein. Ectopic ventricular beats and other arrhythmias have been infrequently seen after adulticide in asymptomatic cats.
Radiology is a screening tests for feline heartworms.
The pulmonary parenchymal changes are non-specific and can change rapidly in infected cats. The lung changes include diffuse or coalescing infiltrates, perivascular densities, and lung atelectasis. The most distinctive radiographic sign is enlarged pulmonary arteries with ill-defined margins. This is most prominent in the caudal lung lobes on the VD view. Blunting and tortuosity of the pulmonary arteries are occasionally seen, but not as common in cats as in dogs.