**3. Standard and alternative outflow graft placement**

The outflow graft is attached to the ascending aorta (AA) in an end-to-side fashion, facilitating blood flow from the LVAD to the systemic circulation, and is considered the standard practice in most LVAD implantations [1, 5, 10]. The recommended and preferred anastomosis site at the AA is at its right concavity, about 2 cm above the sinotubular junction [1, 10] (**Table 3**). In patients with an untouched pericardium (no previous pericardiotomy) for instance, the recommended course of the OG should be intrapericardial, along the inferior right ventricular surface and between the right atrium and pericardium so that the right ventricular outflow tract remains uncrossed [1]. Optionally, tunneling the outflow graft through the transverse sinus with OG anastomosis at the posterolateral aspect of the AA may also be considered [1]. Ultimately, while still preferably connecting it to the AA, routing the OG within the left pleural cavity may also be considered to reduce operative complexity in redo procedures [1].


*Exploring Standard and Alternative Sites for Left Ventricular Assist Device Inflow Cannula… DOI: http://dx.doi.org/10.5772/intechopen.114053*

#### **Table 3.**

*Left ventricular assist device implantation with outflow graft placement to the ascending aorta.*

The ascending aorta is a central conduit in the systemic circulation, making it a logical point to introduce blood pumped by the LVAD to be distributed throughout the body. Attaching the OG to the AA is favored because of the AA's large diameter, good anatomical accessibility, the relative ease with which the anastomosis is completed, postulated in decades of clinical experience. Besides the precise positioning of the IC, however, optimal LVAD performance is equally contingent upon the rigorous positioning of the outflow graft. Traditionally, the AA is the gold standard for OG anastomosis, capitalizing on its central position in the systemic circulation and its presumably resilient anatomy to withstand long-term pressure and flow conditions impaired by the LVAD. That said, the proximal aorta does undergoes dilation under LVAD support [30]. This, on the other side, has been correlated to the development of de novo aortic valve regurgitation, which is more likely to occur in patients with preexisting (before LVAD implant) aortic dilation [30, 31]. These alterations are presumably the results of the LVAD support-induced unphysiological hemodynamics [30, 31]. In this regard, the results of computational fluid dynamics studies confidently advocate for positioning the OG so that it directs the jet of blood towards the lumen of the aortic arch, aiming to prevent turbulent flow, subsequently reducing wall stress and backward pressure in the aortic root [32]. Both in-silico studies and existing clinical data have confirmed that any deviation of the LVAD

outflow jet from the normal flow direction in the AA can lead to flow stasis, aortic root thrombosis, and thromboembolic complications [33–36]. Indeed, a 45° angulation of the outflow graft-to-ascending aorta anastomosis to reduce the risk of de novo aortic valve regurgitation during LVAD support is currently recommended by experts in the field [1]. Nevertheless, the optimal orientation of the OG anastomosis, as well as its distance from the aortic root, are yet to be established in future research [32].

Further, just as the LV's anatomy and function govern the complexities of the inflow cannula's positioning, it is crucial to consider the individual patient's anatomy, comorbid conditions, and potential for complications – and all that in the context of the surgeon's expertise when opting for placement of the OG anastomosis to the standard site. An improperly placed OG might impede natural blood flow, potentially leading to complications such as graft occlusion, turbulent blood flow, or even damage to the aorta itself. Besides that, OG anastomosis to the AA may be nonamenable in patients with hostile chest anatomy or porcelain aorta [1, 10]. Anatomical variations (i.e., severe aortic calcifications, severe chest wall deformities, presence of patent grafts from prior coronary artery bypass surgery, previous AA procedures) or presence of extensive mediastinal adhesions (e.g., post radiation therapy or prior previous cardiac surgery) may deem the surgical access or placement of the OG anastomosis at the AA challenging, high-risk or even prohibitively hazardous, even in experienced hands. To specifically address this, surgical LVAD implantation techniques involving alternative OG landing sites have been developed [1, 10, 37] (**Figure 1**, **Table 4**). Several surgical techniques involving OG placement to the innominate artery, axillary/subclavian artery, descending aorta, or supra-celiac abdominal aorta have been described [4, 32]. While these unconventional sites may offer certain benefits resulting from the less invasive operative technique, like the potentially reduced operative exposure, the use of blood products, the incidence of right heart failure, or avoiding sternotomy in redo surgeries, they come with challenges, including ensuring proper graft orientation and strategies to prevent kinking of the OG and increased operative complexity [10, 38, 39]. In this line of thought, the seemingly indispensable reinforcement of the OG using a (ringed) vascular graft protector has been associated with the development of the unique late complication - OG stenosis, in some patients [40, 41]. Moreover, minimally invasive approaches for LVAD implantation with OG anastomosis to the AA have been standardized, and their benefits are well described [38, 42–44].

#### **Figure 1.**

*Standard and alternative outflow graft anastomosis sites. Schematic depiction of left ventricular assist device placed onto the left ventricular apex with outflow graft anastomosis to the ascending aorta (A), subclavian/ axillary artery (B) and descending aorta (C).*


*Exploring Standard and Alternative Sites for Left Ventricular Assist Device Inflow Cannula… DOI: http://dx.doi.org/10.5772/intechopen.114053*

#### **Table 4.**

*Left ventricular assist device implantation with alternative outflow anastomosis sites.*

Yet, LVAD placement with OG to the left axillary/subclavian artery or descending aorta offers one more advantage, that is, "the preservation of a virgin chest" in patients who are deemed transplant candidates [39, 45]. However, the clinically significant hemodynamic sequelae and long-term outcomes associated with these alternative OG locations are unknown [39, 46], and they are therefore to be regarded as valid but not equal alternatives to the standard OG location [1, 39].

In the end, the choice of OG placement should be determined by a combination of the patient's unique anatomy, clinical history, and the surgeon's expertise, always with an eye on ensuring the longevity and efficiency of the LVAD system.
