A 4-year-old female intact Great Dane was presented to Cornell University Hospital for Animals Emergency service for tachypnea, increased respiratory effort, anorexia and coughing. In January 2016 the patient was diagnosed with asymptomatic dilated cardiomyopathy (DCM) and no treatment other than routine follow up and monitoring was recommended. The patient's heart rate was 156 bpm (60-100) and she had pale pink mucous membranes and was panting with increased bronchovesicular sounds. Initial ultrasound revealed infinity B lines bilaterally indicating interstitial pulmonary edema, and no free fluid. Systolic blood pressure was low at 92 mmHg, SpO2 was 92% on room air, electrocardiogram revealed sinus tachycardia. Her troponin level was elevated at 0.4 ng/mL (0-0.11ng/mL). The patient was given oral pimobendan, nasal oxygen, butorphanol and furosemide continuous rate infusion, until the patient was transferred to Cornell's Cardiology service. Thoracic radiographs showed changes such as cardiomegaly and patchy interstitial to alveolar pattern consistent with congestive heart failure (CHF). An electrocardiogram showed wide QRS complexes, which were indicative of severe left sided heart dysfunction. Echocardiogram revealed a severely dilated left ventricle and fractional shortening of 8.8% (normal >25%) consistent with DCM. The nasal oxygen was gradually reduced and her respiratory rate and effort remained stable. Thoracic radiographs were followed up the next day for re-evaluation and to assess how treatment was working, revealing resolution of the patchy interstitial to alveolar pattern. The stabilized patient was discharged to the care of her owners with pimobendan, furosemide and benazepril. A few weeks later, clinical signs returned and the patient was euthanized at their veterinarian. This senior seminar will discuss a case of acutely decompensated dilated cardiomyopathy. Canine dilated cardiomyopathy is a severe and ultimately fatal disease of cardiac muscle which decreases the ability of the muscle to contract and pump blood through the vascular system. A definitive cause for this condition has not been found but heredity, infection, and nutrition are all felt to play a role. The disease is typically found in large breed dogs such as the Doberman Pinscher, Boxer, Great Dane and paradoxically the Cocker Spaniel.