Massive arteriovenous malformation (AVM). AVMs are congenital vascular lesions associated with a variable degree of arteriovenous shunting. Some of these lesions are thought to originate from arteriovenous connections that have failed to regress during development. The case illustrated in the figure involves the entire left face and neck. Patient shows ulceration and breakdown of the malformation with congestive heart failure (Schöbinger Stage IV).