ECG of the Month.

A 10-year-old 17-kg (37-lb) spayed female Italian Spitz was referred to the Veterinary Teaching Hospital of the University of Bologna because of sudden onset of dyspnea (which occurred 24 hours before the referral examination). The referring veterinarian administered prednisone SC without amelioration of the respiratory problem. A diagnosis of chronic mitral valve disease had been made a few months before, and the dog was currently being treated with furosemidea (1 mg/kg [0.45 mg/lb], PO, q 12 h) and benazepril hydrochlorideb (0.25 mg/kg [0.11 mg/lb], PO, q 24 h). No episodes of acute pulmonary edema were previously observed. On physical examination, the dog was obese (body condition score, 8/9). Mild tachypnea was evident (80 breaths/min), but the dog was extremely anxious. The femoral pulse was rhythmic and strong, and heart rate was considered normal (100 beats/min); an olosystolic left-sided heart murmur (grade 3/6) with maximal intensity over the left cardiac apex was ausculted. Auscultation of the lungs revealed no detectable abnormalities. Survey thoracic radiographic views were obtained, and moderate cardiac enlargement was detected (vertebral heart score, 11.3; vertebral heart score for a clinically normal dog, < 10.21). Pulmonary vessels had a normal appearance, and a mildly diffuse interstitial opacity was attributable to fatty infiltration in an obese dog. Transthoracic echocardiography was performed with an ultrasound unitc equipped with a 1- to 5-MHz phased-array transducer and continuous ECG monitoring. Two-dimensional and Doppler echocardiographic findings included mild mitral valve regurgitation due to chronic valve disease, with mild left ventricular and atrial dilation. Results of a CBC, serum biochemical analysis, and urinalysis were unremarkable. Electrocardiography was performed.