Figure 2: Intracardiac echocardiography documenting two standard views. (a,b) is the bi-caval view without and with color, respectively. This is a tunnel PFO with significant overlap of the septum primum on the septum secundum (the SVC rim). The measurements in the picture is of the length of the tunnel. (c,d) Aortic short-axis view without and with color, respectively. Aortic rim is seen with septum primum overlapping the septum secundum (the aortic rim).