An echocardiographical and clinical pathological investigation of the
rapid loss of weight by a yearling thoroughbred filly revealed an atri
al septal defect, a ventricular septal defect and hyperfibrinogenaemia
. A post mortem examination confirmed the cardiac abnormalities and re
vealed a severe thoracic aortitis. It is proposed that the idiopathic
thoracic aortitis contributed to the horse's compromised cardiovascula
r homoeostasis.