Mature heartworm infection, echocardiogram, cat

Right parasternal 4-chamber echocardiographic view (A) and the same view with color over the tricuspid valve (B) from a 7-year-old spayed female cat with a history of intermittent respiratory distress and syncope in which heartworm antigen and antibody test results were negative. Note the heartworm (hyperechoic parallel lines; arrow) crossing the tricuspid valve. There is mild prolapse of the parietal leaflet of the tricuspid valve leading to mild tricuspid insufficiency. The right atrium is dilated. LA, left atrium; LV, left ventricle; RA, right atrium.