Angiographic evaluation of PFO was routinely performed early in the device closure experience, with fewer operators performing routine angiograms today. With the advent of newer echo techniques (Chap. 5?), angiography is less important to delineate PFO anatomy. Similarly, fluoroscopic balloon sizing of PFO is performed by only 50 % of operators, according to a recent poll at two international meetings (CSI and PICS Meetings, 2010). Despite this trend, balloon sizing offers valuable information regarding PFO anatomy, specifically with the characteristics of the tunnel. Most importantly, angiography plays an essential role in patients with a persistent residual shunt through a previously placed device. Angiography allows the interventionalist to both quantify and delineate the anatomy of the residual defect and is important for choosing the correct type and size of device to use for closure.