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Invited Commentary

Less Invasive Left Ventricular Assist Device Implantation: One Right Step Toward the Future

Mariani, Silvia*; Dogan, Günes*; Schmitto, Jan D.*

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doi: 10.1097/MAT.0000000000001272
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The field of left ventricular assist devices (LVADs) witnessed an important boost after the introduction of the third-generation durable mechanical circulatory support devices. Among the technical improvements which contributed to the success of these LVADs, the miniaturized pump body allowing for a complete intrapericardial implant is surely one of the most interesting. Indeed, the reduced dimensions and the compact design of centrifugal LVADs pushed surgeons to explore new surgical approaches for their implantation.1 This brought to the development of less invasive techniques leading to reduced critical surgical complications2 and increased numbers of patients eligible to receive LVAD implantation for heart failure. The core paradigm of less invasive LVAD surgery is the use of a left lateral thoracotomy (LT) to implant the pump body and avoid a full sternotomy. The first group to apply this technique was based at Hannover Medical School and performed the first LVAD implantation through LT (named LT-VAD) combining an upper hemisternotomy with a left anterolateral thoracotomy in 2011.3 After this early description of the LT-VAD technique, the interest toward this approach has steadily grown,4–8 leading to the Conformité Européenne (CE) mark approval for less invasive implantation of a HeartWare centrifugal-flow ventricular assist device system (HVAD - Medtronic, Inc., Minneapolis, MN) in 2016. Further clinical studies such as the LATERAL Clinical Trial6 (ClinicalTrials.gov Identifier) followed in 2018 and led to the US Food and Drug Administration (US FDA) approval of less invasive HVAD implantation. In the same year, HeartMate3 (Abbott, Chicago, IL) was also implanted through lateral thoracotomy for the first time,9 demonstrating that LT-VAD can be safely applied to different devices.

Nowadays, LT-VAD is routinely performed in hundreds of centers all over the world. Nevertheless, a certain degree of skepticism about the ease of application of this technique might be present in teams which are not familiar with less invasive cardiac surgery. The article by Özer and colleagues10 is a clear answer to this skepticism. In this article, the authors describe their clinical results in the transition phase from conventional LVAD surgery to less invasive LVAD implantation through lateral thoracotomy and upper hemisternotomy.10 They analyzed the outcomes of their first 30 LT-VAD cases and compared them to their last 30 isolated LVAD implants via standard full sternotomy. The authors observed significantly lower mortality rates, shorter cardiopulmonary bypass times, lower postoperative bleedings, less blood products use, shorter intubation times, and shorter intensive care unit stays in the LT-VAD group compared with the conventional sternotomy group.10 Despite an initial longer operation time due to limited experience with LT-VAD, the authors were able to quickly reduce the duration of LT-VAD operations to times comparable to all other cardiac surgeries.10 In summary, the take-home message from Özer et al.10 is that LT-VAD can be safely performed with optimal results also by teams approaching this technique for the first time. Therefore, the transition period to LT-VAD should not be seen as a scary moment by the LVAD team but rather as a growing opportunity. Of note, to turn the transition phase into a positive experience, the new LT-VAD team should always be guided through a proper training phase by LT-VAD expert proctors. A proper LT-VAD training program should start with theoretical sessions and surgical hands-on-courses. Afterward, the new LT-VAD team should visit highly specialized centers to observe less invasive LVAD procedures. This will allow surgeons to interact with LT-VAD experts and receive insight into the management of LT-VAD patients. Finally, the latest training phase should focus on a one-to-one proctorship led by experienced LT-VAD surgeons. When the new LT-VAD team starts operating independently, surgeons should pay attention to patient selection as done by Özer et al.10 The complexity of patients chosen for LT-VAD implantation should be gradually increased starting with isolated LVAD implantations and then proceeding to patients requiring LVAD implantation as a redo operation. Indeed, this group of patients benefits most from LT-VAD in terms of surgical invasiveness, minimized adhesiolysis and raw surface bleeding. Lately, when full experience with isolated LVAD implantation is acquired, combined procedures can be approached. This will allow the new LT-VAD team to maintain high standards and even better results with a less invasive surgical approach.

Once full experience with LT-VAD is gained and consolidated, the team can start applying the use of a lateral thoracotomy to more complex cases. For instance, some patients require an alternative approach for outflow graft positioning. Normally, the outflow graft is tunneled intrapericardially, or in redo cases, through the left pleural space. In case of open bypass grafts, the outflow graft can be tunneled safely above left mammary artery or to the right pleural cavity. Tunneling of the outflow graft through the transverse sinus is also possible and guarantees protection of the outflow graft in future operations.11 In case of a severely diseased aorta, surgeons can consider alternative target vessels such as the brachiocephalic artery12 exposed through an upper hemisternotomy, the left or right subclavian artery13,14 exposed through a local incision, or the descending aorta exposed through an extended left thoracotomy.15 This latest option has been analyzed in details by Kawabori and colleagues15 who reported on eight patients undergoing HVAD implantation for destination therapy via a left subcostal or lateral thoracotomy and outflow graft anastomosis to the descending aorta. The main concern with this approach is the nonphysiologic flow of an LVAD primarily designed to perfuse the ascending aorta and give a forward flow to the supra-aortic vessels and the whole body. Kawabori et al.15 observed no pump thrombosis or ischemic neurologic events in patients receiving outflow graft anastomosis to the descending aorta. However, in one patient, the aortic valve was not opening and led to aortic root thrombosis in the perioperative period. This event can occur when the pump flow is directed in the descending aorta. In these patients, a careful follow-up with regular echocardiography controls should be performed to exclude flow stasis in the aortic root. These patients might require lower pump speeds to favor aortic valve opening every one to four beats and aortic root washout. This can prevent stasis in the ascending aorta, thus decreasing the risk of clot formation and stroke. In parallel, medical therapy should be optimized to support the cardiac function in severely compromised patients who usually need higher pump speeds. Despite these “tips and tricks,” robust reports on postoperative outcomes of patients undergoing outflow graft anastomosis to the descending aorta are still lacking and this technique should be applied only in patients where all other LT-VAD options are not applicable.

Both articles by Özer et al.10 and Kawabori et al.15 nicely highlight how LT-VAD and sternal-sparing techniques are gaining popularity in the LVAD field due to their versatility and safety also in complex patients. Worth mentioning, LT-VAD techniques demonstrated to be associated with optimal clinical results but also with advantages in terms of cost-effectiveness.16 A comparison between Medicare data for LVAD implantation and costs derived from the LATERAL Clinical Trial6 demonstrated that mean total index hospitalization costs for thoracotomy were 21.6% lower compared with conventional sternotomy.17 Additionally, Mahr et al.16 demonstrated an incremental cost-effectiveness ratio of $64,632 per quality-adjusted life year in LT-VAD patients.

Finally, we can say that all these positive effects of the LT-VAD approach have surely contributed to the significant growth of the LVAD field in the recent years. The outlook to the future is even more promising based on the upcoming technical developments of LVADs including higher hemocompatibility and biocompatibility, further miniaturization, telemedicine technologies, pressure and flow measurements, antisuction algorithms, versatile devices able to adapt to different needs, exercise and circadian autoregulation, new battery generations, and transcutaneous energy transfer. In conclusion, the future of LVADs will surely match less traumatic implantation approaches, futuristic engineering, and a fruitful innovative and interdisciplinary field leading toward excellent results for heart failure patients.

References

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