**6.5 Development of collateral vessels**

Systemic venous to pulmonary venous and systemic arterial to pulmonary arterial collateral vessels may develop in some patients after the Fontan procedure [88, 95]. These may develop both shortly after the procedure and during late followup. Systemic venous to pulmonary venous collateral vessels produce arterial hypoxemia. In addition, they may also become potential sites for paradoxical embolism.

### **Figure 12.**

*(A) Selected frame from a cineangiogram of a Fontan conduit in lateral view, illustrating a thrombus (arrow in (A)). (B) and (C) position of a stent (St) before (B) and after (C) its complete expansion. (D) Cineangiographic frame demonstrating the widely patent stent after stent deployment. Also, note the residual shunt (RS) at the superior aspect of the conduit (seen in (A) and (D)). The RS was occluded with an Amplatzer septal occluder device (AD) shortly after the cine shown in (D). (F) A follow-up cineangiogram 1 year later shows the continued patency of the conduit with no RS. TEE, transesophageal echo probe (Reproduced from [94]).*

Systemic arterial to pulmonary arterial (or venous) collateral vessels produce left ventricular volume overload. These abnormal vessels should be transcatheteroccluded with coils, vascular plugs, and ductal occluding devices depending upon the size and accessibility. Examples from the author's experience of occluding these vessels are shown in **Figures 13**–**16** [88, 95, 96].
