Implantation of the HeartWare HVAD: from full sternotomy to less invasive techniques

Off-pump implantation of left ventricular assist device via minimally invasive left thoracotomy: Our single-center experience

Background

The aim of this study was to compare our experience of left ventricular assist device implantation via minimally invasive left thoracotomy with off-pump versus on-pump technique.

Methods

Between June 2013 and April 2020, nine patients (8 males, 1 female; mean age: 47±11.9 years; range, 30 to 61 years) who underwent off-pump left ventricular assist device implantation and nine patients (8 males, 1 female; mean age: 47±11.4 years; range, 29 to 60 years) who underwent on-pump minimally invasive left thoracotomy were retrospectively analyzed. Postoperative outcomes and mid-term results of both groups were evaluated.

Results

Outflow graft was anastomosed to the ascending aorta with J-sternotomy in all patients. The median duration of intubation and intensive care unit stay were one (IQR: 1.5) day and eight (IQR: 6.5) days in the off-pump group, respectively and one (IQR: 0) day and seven (IQR: 7) days in the on-pump group, respectively. Intra-aortic balloon pump was needed during the weaning of cardiopulmonary bypass in one (11%) of the patients in both groups. Postoperative right ventricular failure was observed in two (22%) patients in the offpump group who were treated medically and recovered. There was no need for revision due to bleeding or postoperative extracorporeal membrane oxygenator implantation in either group. In the off-pump group, three patients underwent heart transplantation after median 854 (IQR: 960) days. Three patients died one month, two and four years after implantation. Three patients were still alive with left ventricular assist device and were being uneventfully followed for 365, 400, and 700 days after implantation.

Conclusion

Off-pump technique is safe and feasible option for implantation of left ventricular assist device via minimally invasive left thoracotomy.

Clinical overview of the HVAD: a centrifugal continuous-flow ventricular assist device with magnetic and hydrodynamic bearings including lateral implantation strategies

Growing worldwide incidences of end-stage heart failure and declining rates of cardiac transplants have given rise to the need for alternative treatment options, based on mechanical circulatory support (MCS) devices such as left ventricular assist devices (LVADs). Technologically advanced LVADs such as the HVAD^® (HeartWare^®, Medtronic) facilitate safe and efficient treatment of heart failure patients with reduced post-operative complications, which is attributed to their considerably miniaturized size. This also facilitates the development and implementation of novel, minimally-invasive surgical techniques. The HVAD is a centrifugal pump, manufactured by HeartWare Inc., (Framingham, MA, USA) and subsequently by Medtronic Inc., (Minnesota, MN, USA), and has been approved for clinical application after receiving the CE Mark approval in 2008 and the FDA approval in 2012. Current research efforts are focused on further miniaturization alongside optimization of electronic and software controllers as well as implementation of the transcutaneous energy transfer (TET) technology. Salient features of the HVAD pump technology, clinical applications and future optimization strategies have been discussed in this article.

Contrast Microsphere Destruction by a Continuous Flow Ventricular Assist Device: An In Vitro Evaluation Using a Mock Circulation Loop

OBJECTIVES

Transthoracic echocardiography (TTE) is fundamental in managing patients supported with ventricular assist devices (VAD). However imaging can be difficult in these patients. Contrast improves image quality but they are hydrodynamically fragile agents. The aim was to assess contrast concentration following passage through a VAD utilising a mock circulation loop (MCL).

METHODS

Heartware continuous flow (CF) VAD was incorporated into a MCL. Definity® contrast was infused into the MCL with imaging before and after CF-VAD. 5 mm2 regions of interest were used to obtain signal intensity (decibels), as a surrogate of contrast concentration.

RESULTS

Four pump speeds revealed significant reduction in contrast signal intensity after CF-VAD compared to before CF-VAD (all p < 0.0001). Combined pre- and postpump data at all speeds showed a 22.2% absolute reduction in contrast signal intensity across the CF-VAD (14.8 ± 0.8 dB prepump versus 11.6 ± 1.4 dB postpump; p < 0.0001). Mean signal intensity reduction at each speed showed an inverse relationship between speed and relative reduction in signal intensity.

CONCLUSION

Contrast microsphere transit through a CF-VAD within a MCL resulted in significant reduction in signal intensity, consistent with destruction within the pump. This was evident at all CF-VAD pump speeds but relative signal drop was inversely proportional to pump speed.