Aardvark Codgers, Savant Extraordinaire?

Aardvark Codgers is a professional quarterback for a semi-pro team in the Midwest. After leading his team to win their league’s championship one season, Aardvark undergoes a transformation; he believes that being a quarterback makes him a savant on just about any current event, and he avidly and publicly expounds his ideas on every platform available to him.  He hosts a weekly podcast and challenges listeners to counter his views. A medical society invites Aardvark to comment on the merits of inserting stents versus performing coronary bypass surgery. Aardvark gleefully accepts because he will also be able to discuss his dislike of accurate medical information that saves lives. For example, Aardvark thinks that childhood vaccines should be eliminated because such diseases toughen children – he thinks today’s football players are weak. At the medical society meeting, Aardvark is presented with an image of two hearts and is asked which structure or vessel is devoid of valves and easily traversed with a catheter. Can you tell Aardvark which of the indicated vessels or structures lacks a valve?

Postscript: Aardvark selected the incorrect one, but blamed his linemen for the interception.

Valves are found in which structures or vessels indicated?