Mitral Valve Dysplasia Leading to Congestive Heart Failure in a Male Squirrel Monkey (Saimiri boliviensis boliviensis)

Acquired cardiovascular diseases are recognized as a major age-related cause of morbidity and mortality in captive squirrel monkeys (Saimiri spp.). An 11-year-old intact male black-capped squirrel monkey (Saimiri boliviensis boliviensis) was presented following a syncopal episode associated with respiratory distress, abdominal distension, and peripheral edema. Upon presentation, the animal appeared thin and debilitated. Physical examination revealed respiratory distress with paradoxical breathing, abdominal distension, peripheral edema of the hind limbs, and hypothermia. Thoracic auscultation identified a loud systolic murmur over the left hemithorax and diffuse pulmonary crackles. Thoracic radiographs demonstrated severe cardiomegaly and perihilar pulmonary interstitial pattern consistent with cardiogenic pulmonary edema. Two-dimensional echocardiography revealed hyperechoic papillary muscles, thickened and restricted mitral valve leaflets, and shortened chordae tendineae with secondary severe left atrial and ventricular dilation. Doppler echocardiography demonstrated severe mitral regurgitation. Congestive heart failure secondary to mitral valve dysplasia was diagnosed. Treatment with diuretics and vasodilators resulted in transient clinical improvement followed by rapid deterioration of the patient’s condition; therefore, euthanasia was elected. Gross pathological and histopathological examinations revealed thickened and irregular mitral valve leaflets with hypoplastic chordae tendineae associated with severe left-sided cardiac enlargement. To the authors’ knowledge, this is the first report describing mitral valve dysplasia in an adult squirrel monkey. This report expands the spectrum of cardiovascular diseases described in squirrel monkeys and highlights the importance of advanced cardiac imaging in the diagnosis of rare congenital cardiac defects in non-human primates.