A n 8-year-old, 2.8 kg, female spayed domestic shorthair cat was admitted to the Small Animal Clinic of the Louisiana State University Veterinary Teaching Hospital (LSU VTH) with a 5-day history of anorexia, lethargy, and dyspnea.Recent medical history included a vaginoplasty performed at LSU VTH 3 weeks earlier, to resect vulvar adhesions causing urinary tract outflow obstruction, stranguria, and chronic cystitis. At that time, physical examination of the cardiovascular system and results of routine CBC and serum biochemical profile were unremarkable. An abdominal ultrasound examination was performed, revealing urinary bladder and urethral dilatation, and a small round structure with anechoic content in the perivulvar region. At surgery, this tissue was resected. It resembled a fibrous band of connective tissue and was not submitted for histopathologic evaluation. The cat was current on vaccinations, and was negative for feline leukemia virus antigen and feline immunodeficiency virus antibodies.Upon presentation to the Small Animal Clinic, the cat was laterally recumbent, in respiratory distress (80 breaths per minute), hypothermic (961F), had a heart rate of 190 beats per minute and arterial femoral pulses were judged to be weak. Diffuse pulmonary crackles were heard bilaterally on thoracic auscultation. Thoracic radiographs (lateral and dorsoventral views) indicated severe, generalized cardiomegaly, enlarged pulmonary veins, and an interstitial to alveolar pattern in the caudodorsal lung fields. These findings were interpreted as indicating congestive heart failure with pulmonary edema. A complete blood count indicated mild, normocytic, normochromic, nonregenerative anemia (PCV 28%; reference range, 30-48%; hemoglobin, 9.7 g/dL; reference range, 12-15.5 g/dL). Serum biochemical abnormalities included hypoproteinemia (4.9 g/dL; reference range, 6.5-8.7 g/dL), increased aspartate aminotransferase activity (100 U/L; reference range, 0-60 U/L), mildly increased urea nitrogen concentration (58 mg/dL; reference range, 18-30 mg/dL), and hyperphosphatemia (7.5 mg/dL; reference range, 4-6.6 mg/dL). Plasma thyroxine concentration was reported to be normal in the cat's recent medical records and the test was not repeated. Average systolic blood pressure recorded by the Doppler method during the initial visit at LSU VTH was 135 mmHg before anesthesia. The cat was treated with furosemide a (3 mg/kg IV), and placed in a 40% humidified oxygen cage on a warming blanket.After initial stabilization and mild improvement of the respiratory signs, a transthoracic echocardiogram was obtained to evaluate the possible underlying cardiac disease. The 2-dimensional echocardiographic findings included a moderate amount of pericardial effusion and diastolic collapse of the right atrium, indicating cardiac tamponade. The left atrium was considered mildly enlarged (LA/Ao 5 1.7; normal o1.5). The left ventricular free wall was markedly thickened (9.5 mm in diastole in a right parasternal short-axis view; normal o6 mm). Left ventricular pap...

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