Left Atrial Paraganglioma in a Dog: Echocardiography, Surgery, and Scintigraphy

rimary tumors of the left atrium are uncommon in dogs P and tumor-specific diagnoses have been made only at necropsy.'.'No reports have been found in which the diagnosis was confirmed antemortem and the tumor removed surgically.This report describes a case of obstructive paraganglioma in the left atrium of a dog and long-term survival after surgical removal of most of the tumor using cardiopulmonary bypass.Subsequently, scintigraphy demonstrated the presence of somatostatin receptors in residual tumor in the left atrium.The latter technique may be of value in establishing a definitive diagnosis in future cases of chemodectoma, extra-adrenal paraganglioma, or adrenal paraganglioma (pheochromocytoma). Case ReportA 9-year-old, 15-kg, female Brittany was referred for evaluation because of a systolic heart murmur and an episode of coughing and pulmonary crackles 10 days earlier.A CBC and serum chemistry analysis at that time were normal.A change in the character of the dog's bark had been noted earlier by the owners after the dog returned from 2 years on a Texas hunting farm.The dog was in good condition and had normal stamina when used extensively for hunting.The respiratory signs resolved after treatment with furosemide and trimethoprim sulfonamide.Examination at the veterinary hospital of the University of Pennsylvania revealed a localized, left apical, grade 2/5 holosystolic murmur but was otherwise unremarkable.Breath sounds were normal and femoral pulses were strong.Slightly wide (0.06 seconds), notched P waves were present on an electrocardiogram.A large left atrium that compressed the left main stem bronchus was observed on thoracic radiography (Fig 1).In dorsoventral projection, the left atrial appendage was not prominent.A 4.5 X 6.5-cm diameter, ovoid mass almost filling the left atrium was observed on 2-dimensional echocardiography (Fig 2).Color Doppler recordings showed that the mass partially obstructed forward flow through the mitral orifice (Fig 3).Spectral Doppler recordings showed sustained diastolic flow through the mitral orifice suggestive of mitral valve stenosis (Fig 4).Trivial mitral regurgitation also was noted.A tentative diagnosis was made of left atrial myxoma with ball valve obstruction.The prognosis was considered grave with no hope for survival without open heart surgery.The owners were advised to expect the dog to experience syncope or collapse within days or weeks.