Congenital isolated left ventricular non-compaction in two juvenile dogs.

Two juvenile (five- and 10-month-old), male, neutered, Jack Russel terrier cross dogs, each presented primarily for respiratory signs of varying severity, were included in the study. The first presented for coughing and weakness, and the other presented in respiratory distress. A cardiac murmur was absent in both. Imaging findings were strikingly similar for both dogs. Thoracic radiography revealed severe, disproportionate left atrial dilation with otherwise normal cardiac silhouette shape and size. Echocardiography revealed severe left ventricular mural thickening with hypertrabeculation and marked left atrial enlargement consistent with a diagnosis of congenital, isolated left ventricular non-compaction. Both dogs deteriorated clinically and were humanely euthanised without necropsy.