Right-to-left shunting following left atrial decompression in three dogs.

Three dogs with advanced myxomatous mitral valve disease underwent left atrial decompression (LAD) via transseptal puncture and balloon atrial septostomy as a palliative treatment for refractory left-sided congestive heart failure. Variable degrees of pulmonary hypertension were present at the time of LAD. Each dog initially exhibited predominantly left-to-right shunting across the iatrogenic atrial septal defect but subsequently developed clinically relevant right-to-left shunting in the postoperative period. Progressive hypoxaemia, haemodynamic instability and clinical deterioration occurred in all cases, culminating in death or euthanasia. Right-to-left shunting following LAD has not been previously reported in dogs. These cases illustrate the potential for adverse shunt reversal in dogs with and emphasize the importance of careful case selection and postprocedural monitoring.