Dr O’Sullivan received her Doctor of Veterinary Medicine degree from the Atlantic Veterinary College, University of Prince Edward Island in 1998. Following graduation, she completed a small animal rotating internship at the Ontario Veterinary College (OVC), University of Guelph. Then she went on to complete a clinical residency in Cardiology and a Doctor of Veterinary Science graduate degree, investigating dilated cardiomyopathy in the Doberman pinscher, also at OVC from 2000-2003. Dr. O’Sullivan received board certification in Cardiology by the American College of Veterinary Internal Medicine (ACVIM) in 2003. Following this she became a part of the clinical Cardiology service in the OVC Health Sciences Centre, teaching veterinary undergraduate and graduate students and contributing to clinical investigations.