Myocardial infarction complicating management of congestive heart failure in a dog.

A 7.5-kg, 10-year-old, spayed female, mixed-breed dog was evaluated for sudden onset of weakness, tachypnea, and an irregular cardiac rhythm. Congestive heart failure secondary to mitral valve regurgitation had been diagnosed six weeks earlier. The dog was stable on furosemide, enalapril, and hydralazine. Complex ventricular tachycardia, altered QRS conformation of sinus complexes, echocardiographic evidence of a hypokinetic left-ventricular free wall, and elevated creatine kinase suggested a diagnosis of myocardial infarction. Despite antiarrhythmic therapy, the dog developed ventricular fibrillation and died 36 hours after admission. Postmortem examination confirmed the myocardial infarction. Although a rare diagnosis in the veterinary patient, myocardial infarction must be considered in the differential diagnosis for sudden onset of weakness, tachypnea, and ventricular tachycardia.