Quinidine sulphate cardioversion in a Holstein with persistent atrial fibrillation

Abstract

Divine, a three-year-old Holstein show cow, presented to Cornell University’s Equine and Farm Animal Hospital on Christmas Day 2008, with a 24-hour history of inappetance, scant manure, intermittent colic, and suspicion of small intestinal obstruction. Bloodwork revealed a severe hypochloremic metabolic alkalosis, hypocalcemia, and hyperlactatemia; there was an irregularly irregular arrhythmia (atrial fibrillation) on auscultation. At exploratory abdominal surgery, no abnormalities were found. Divine recovered quickly with IV fluid therapy, but the arrhythmia persisted. Due to concerns of decreased milk production, shortened productive life, and progression into congestive heart failure, and considering the exceptional genetic value of the cow, cardioversion was attempted 14 days into hospitalization using an intravenous solution of compounded filtered quinidine sulphate tablets. The cow did not convert to normal sinus rhythm; an investigation revealed sub-therapeutic plasma quinidine concentrations. A second attempt was made on day 21 using digoxin and a quinidine solution compounded from powdered product; target plasma concentrations were achieved successfully. Unfortunately, the cow did not convert to normal sinus rhythm and was discharged at day 29 with persistent atrial fibrillation. At six-month follow-up, the cow had freshened and was producing 90-100 lbs. milk/day, and despite atrial fibrillation, had no other clinical signs of cardiac disease.