Idiopathic spontaneous intracardiac microbubbles in an adult dog

A four-year-old, female neutered English springer spaniel presented for evaluation of exercise intolerance, panting and lingual cyanosis. Echocardiography revealed a structurally and functionally normal heart with the presence of spontaneous intracardiac microbubbles entering the right side of the heart from the caudal vena cava. A cause for the clinical signs could not be identified; routine blood work, urinalysis and electrocardiography were unremarkable. Testing for tick-borne diseases, clotting times, cardiac biomarkers, thyroid function and basal cortisol were all within normal limits. Faecal samples tested for Clostridium perfringens alpha, beta and epsilon toxins were negative. Genetic conditions including malignant hyperthermia and phosphofructokinase deficiency were excluded. Computed tomography and angiography of the abdomen and thorax revealed no abnormalities or shunting vessels that could explain the origin of the spontaneous intracardiac microbubbles. Previously, microbubbles have only been visualised when intravenous access is present or when purposeful contrast studies are performed. As far as the authors are aware, this is the first case of spontaneous intracardiac microbubbles visualised in the right heart of a dog with no identifiable underlying systemic conditions.