**6.3 Residual arterial desaturation and paradoxical emboli**

Sometimes connections between lateral tunnel and extra-cardiac conduit on the one hand and the atrium on the other persist. These residual defects and intentionally created Fontan fenestrations result in right-to-left shunt because the pressure in the Fontan conduit is higher than that of the atrial pressures. These residual defects will result in arterial desaturation and may become the site of paradoxical embolism with consequential transient ischemic attacks (TIAs), cerebrovascular accidents (CVAs), and systemic emboli. These residual defects as well as Fontan fenestrations should be occluded by transcatheter techniques

### **Figure 11.**

*Selected frames from cineangiograms of the pulmonary artery in posteroanterior view illustrating normal right pulmonary artery (RPA) and narrowed (arrow) left pulmonary artery (LPA) prior to (a) and after (b) stent (arrow) placement in an adolescent who had Fontan surgery several years earlier (Reproduced from [88]).*

to return O2 saturations to normal and decrease the likelihood for paradoxical embolism [30, 32, 33, 83, 88, 89]. Amplatzer septal occluder (St. Jude Medical, Inc., St Paul, MN) is currently most common device used to accomplish this (**Figures 7, 8**, and **10**). Tubular fenestrations may be closed with Amplatzer vascular plug devices (St. Jude Medical, Inc.) (**Figure 9**). Test occlusion of the residual defect or fenestration is suggested to ensure that adequate cardiac output is maintained following defect occlusion [89, 90], especially if the procedure is performed shortly after fenestrated Fontan. Late follow-up results of fenestration closure are good [33].

## **6.4 Thrombus formation**

There is a tendency for thrombus formation in the Fontan pathway; the reported prevalence was 15–30% [91, 92]. Regrettably the usual transthoracic echo-Doppler

**143**

**Figure 12.**

*Fontan Operation: A Comprehensive Review DOI: http://dx.doi.org/10.5772/intechopen.92591*

evaluation may not discover these thrombi. However, transesophageal echocardiography, MRI, or CT studies may be necessary to detect these thrombi. In an attempt to

commonly recommended; both warfarin and aspirin have been utilized in the past for this purpose. A multicenter, randomized trial was conducted to compare the efficacy of these two drugs; results showed less than optimal results with both drugs and no significant difference between the two regimens [93]. In the author's experience, most children are prescribed with aspirin for thromboprophylaxis which may

Despite seemingly adequate thromboprophylaxis, some patients develop thrombosis of the Fontan conduits (**Figure 12A**). We initially employ thrombus dissolving drug therapy (tPA, heparin, etc.). If the thrombi do not resolve, we have employed stenting of the conduit to compress the thrombi against the conduit wall [94]. An

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.

*(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]).*

prevent thrombus formation in the Fontan circuit, thromboprophylaxis is

be switched to clopidogrel (Plavix) as the children approach adulthood.

example from our experience is shown in **Figure 12**.

**6.5 Development of collateral vessels**

### *Fontan Operation: A Comprehensive Review DOI: http://dx.doi.org/10.5772/intechopen.92591*

*Advances in Complex Valvular Disease*

**142**

**Figure 11.**

closure are good [33].

**6.4 Thrombus formation**

to return O2 saturations to normal and decrease the likelihood for paradoxical embolism [30, 32, 33, 83, 88, 89]. Amplatzer septal occluder (St. Jude Medical, Inc., St Paul, MN) is currently most common device used to accomplish this (**Figures 7, 8**, and **10**). Tubular fenestrations may be closed with Amplatzer vascular plug devices (St. Jude Medical, Inc.) (**Figure 9**). Test occlusion of the residual defect or fenestration is suggested to ensure that adequate cardiac output is maintained following defect occlusion [89, 90], especially if the procedure is performed shortly after fenestrated Fontan. Late follow-up results of fenestration

*Selected frames from cineangiograms of the pulmonary artery in posteroanterior view illustrating normal right pulmonary artery (RPA) and narrowed (arrow) left pulmonary artery (LPA) prior to (a) and after (b) stent (arrow) placement in an adolescent who had Fontan surgery several years earlier (Reproduced from [88]).*

There is a tendency for thrombus formation in the Fontan pathway; the reported prevalence was 15–30% [91, 92]. Regrettably the usual transthoracic echo-Doppler

evaluation may not discover these thrombi. However, transesophageal echocardiography, MRI, or CT studies may be necessary to detect these thrombi. In an attempt to prevent thrombus formation in the Fontan circuit, thromboprophylaxis is commonly recommended; both warfarin and aspirin have been utilized in the past for this purpose. A multicenter, randomized trial was conducted to compare the efficacy of these two drugs; results showed less than optimal results with both drugs and no significant difference between the two regimens [93]. In the author's experience, most children are prescribed with aspirin for thromboprophylaxis which may be switched to clopidogrel (Plavix) as the children approach adulthood.

Despite seemingly adequate thromboprophylaxis, some patients develop thrombosis of the Fontan conduits (**Figure 12A**). We initially employ thrombus dissolving drug therapy (tPA, heparin, etc.). If the thrombi do not resolve, we have employed stenting of the conduit to compress the thrombi against the conduit wall [94]. An example from our experience is shown in **Figure 12**.
