A 7-year-old Spanish Sport Horse was referred to the University of Cordoba for evaluation of an irregular heart beat that was identified during a prepurchase examination. At rest during the initial examination, heart rate was 35 beats/min and cardiac sounds were rhythmic; no cardiac murmurs were auscultated. Cardiac auscultation performed after exercise revealed a clearly audible arrhythmia during the recovery period. No other abnormalities were detected during the physical examination.
Diagnostic procedures were undertaken and included echocardiography and clinicopathologic analyses (hematologic and serum biochemical analyses). No abnormalities were detected during the ECG examination. Serum potassium concentration (3.4 mmol/L; reference range, 3.3 to 4.5 mmol/L) and creatine kinase activity (131 U/L; reference range, 60 to 350 U/L) were within reference ranges. The WBC count and serum fibrinogen concentration (markers of inflammation) were not high (5,900 cells/μL [reference range, 5,400 to 14,000 WBCs/μL] and 200 mg/dL [reference range, 130 to 400 mg/dL], respectively). Electrocardiographic recordings were obtained before and after exercise (Figure 1).
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