There are life-threatening complications caused by abnormal venous-to-arterial communications. These may be intracardiac, such as seen in a ventricular septal defect, atrial septal defect, or patent foramen ovale (PFO). Pulmonary arteriovenous malformation (PAVM) is an extracardiac cause of an abnormal communication.
Complications resulting from such abnormalities include cerebrovascular accidents, transient cerebral ischemic events, and cerebral abscesses. PAVM complications include the above complications plus hemoptysis and hemothorax.