Assessment of Ventricular Assist Device Placement and Function



Fig. 14.1
D-TGA 3D virtual model (left) and corresponding printed model (right) of the pulmonary venous baffle (PVB) to the systemic right ventricle (RV) in a 36 yo patient with D-TGA s/p Mustard procedure in HF. The model is viewed from the anterior aspect (a) and leftward aspect (b). The anatomic landmarks of interest, i.e., the prominent trabeculations of the systemic RV and the moderator band (MB) were well reproduced. This would allow presurgical planning of cannula placement as to avoid possible inflow obstruction due to these trabeculations. Right atrium (RA), right ventricular cavity (RVC), aorta (Ao)



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Fig. 14.2
L-TGA 3D virtual model (left) and corresponding printed model (right) in a 51 yo patient with L-TGA in HF. The model is viewed from the anterior aspect (a) and leftward aspect (b). The prominent systemic right ventricular (RV) trabeculations and an anterior and leftward aorta are clearly identified, allowing accurate presurgical planning. Superior vena cava (SVC), right atrium (RA), left ventricle (LV), pulmonary artery (PA), right ventricular cavity (RVC)


In addition to cannula positioning, surgical approach may need modification due to the variation in the location of the RV in patients with D-TGA and L-TGA. In patients with D-TGA, the RV is anterior and rightward similar to normal anatomy, whereas in L-TGA, it is leftward, in the usual LV position. In these patients, placement of a VAD in the right abdomen instead of the left can cause compression of right-sided structures which requires close monitoring in the postoperative setting. This global arrangement of cardiac chambers and other nearby organs is notable by routine cardiac CT or MRI but can be spatially enhanced by 3D modeling to add to preoperative surgical approach.



Fontan Palliation


Patients born with a severely underdeveloped ventricle in whom the circulation is only supported by a single ventricle are currently palliated with a Fontan procedure. This palliative strategy involves creation of a pathway from the inferior vena cava to the pulmonary artery and leaves the sole functioning ventricle to supply the systemic circulation [24]. The major forms of CHDs that typically require the Fontan palliation include hypoplastic left heart syndrome, tricuspid atresia, and double inlet LV. During the Fontan palliation, venous blood flows passively to the pulmonary arteries. In the long term, this circulation is associated with an approximate failure rate of 30% in a 20-year follow-up [25]. The major co-morbidities of the Fontan palliation include protein losing enteropathy (PLE), plastic bronchitis, thromboembolism, bleeding diathesis, atrial arrhythmias, and liver cirrhosis [26, 27].

Adults with a failing Fontan circulation are commonly poor candidates for heart transplantation due to chronic malnutrition, major co-morbidities, and significant end organ dysfunction. For such patients, VAD placement may be an option to reach hemodynamic stability, rehabilitate end organ function, and possibly regain candidacy for heart transplantation. There is only limited experience with VAD implantation in patients with the Fontan circulation in either the right-sided circulation or the failing systemic ventricle. Pretre et al. reported a case of insertion of a Berlin Heart in a patient with a failing Fontan after a conversion procedure with a normal functioning systemic ventricle. The cavopulmonary anastomosis was taken down, and chambers were created for inflow and outflow cannulation. The outflow cannula to the pulmonary artery was implanted in the proximal stump of the Fontan conduit. A capacity chamber was created with anastomosis to the superior vena cava with an enlargement patch of xenopericardium and to the inferior vena cava. The inflow venous cannula was inserted in this capacity chamber. Both cannulas were externalized and connected to a 60-ml paracorporeal ventricle. Postoperatively, the patient had marked recovery of end organ function and went on to receive cardiac transplantation after 13 months of mechanical circulatory support [28]. Newcomb et al. described a case of ventricular failure after Fontan conversion which needed VAD implantation. In this report, VAD cannulation was done through the apex of the heart and ascending aorta, and the patient was eventually bridged to cardiac transplantation [29].


Challenges to VAD Placement in the Fontan Circulation


Although the cases above demonstrate feasibility of VAD implantation in patients with a failing Fontan circulation, there remains a paucity of reported experience of successful bridging of such patients to cardiac transplantation. In cases of right-sided circulatory failure with preserved function of the systemic ventricle, the cavopulmonary anastomosis may require deconstruction prior to creation of pathways for the VAD cannulas. A major challenge is to accomplish simultaneous drainage of systemic venous blood from superior and inferior vena cava into the VAD inflow cannula. As reported above, after takedown of the cavopulmonary anastomosis, systemic venous drainage is possible by creation of a capacity chamber between the superior and inferior vena cava, which is connected to the VAD inflow cannula. Prior to takedown of the cavopulmonary anastomosis, it is imperative to preoperatively assess for leaks and stenosis within the Fontan and to comprehend the spatial relationship between major vascular structures and collaterals to prevent adverse hemorrhagic complications. In cases, where the systemic ventricle is failing, several precautions are noteworthy during implantation of the VAD. These include precisely localizing the apex which may be displaced or not in communication with the major ventricular chamber and delineation of the surface coronary anatomy [28, 29]. Preoperative 3D modeling of the Fontan circulation, Fig. 14.3, may further aid in comprehending the anatomical arrangement of the cavopulmonary anastomosis, global orientation of the systemic ventricle, and the spatial orientation of nearby vascular structures for optimal preoperative surgical approach and planning.

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Fig. 14.3
Fontan A 3D virtual model (left) and corresponding printed model (right) in a 37-year-old patient with tricuspid atresia, d-transposed great vessels s/p Fontan procedure with persistent ascites and atrial arrhythmias. The model is viewed from the anterior aspect (a) and from the posterior aspect (b). The Fontan pathway (FP) and its spatial relationship with the rest of the anatomy are well represented on the 3D model and can be used to plan VAD placement using any of the techniques mentioned earlier. Superior vena cava (SVC), right atrium (RA), right ventricle (RV), left ventricle (LV), right pulmonary artery (RPA), left pulmonary artery (LPA), left atrium (LA), aorta (Ao)

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Oct 11, 2017 | Posted by in CARDIOLOGY | Comments Off on Assessment of Ventricular Assist Device Placement and Function
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