Right ventricular failure in left ventricular assisted patients

2017-02-22T23:39:40Z (GMT) by Lo, Casey
In patients with refractory end-stage heart failure, cardiac transplantation remains the only established, definitive treatment option endorsed by the current American Heart Association guidelines (1). However, owing to the limited number of available organs and the increasing numbers of patients surviving but remaining unsuitable for transplantation, there has been intense interest in the development of mechanical circulatory support options as destination therapy and bridge-to-transplant. This has led to the development and adoption of left ventricular assist devices (LVAD). The Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) trial demonstrated both survival benefit and quality of life improvement for patients with LVAD implanted (2). However, even with all the benefits it provides, LVAD technology has not proven to be the panacea that was hoped for. The most prominent amongst the technical challenges to be overcome has been the persistence in the right ventricular (RV) failure rate post LVAD implantation. The incidence of post-operative right ventricular dysfunction after LVAD implantation ranges from 20 to 50% (3). As well as increasing morbidity, the mortality of the peri-operative period increases from 19% to 43% (3). To further complicate matters, the transition from pulsatile flow left ventricular assist devices (LVAD) to continuous flow has necessitated a re-validation of knowledge in this technology. In Victoria, The Alfred serves as the quaternary referral centre for cardiothoracic transplant and mechanical cardiovascular support services. At The Alfred, these patients are usually either heart transplant waiting list patients who deteriorate while awaiting donor organ availability for transplantation, or new rapidly deteriorating patients who have not yet been assessed for eligibility for transplantation, but require urgent mechanical support. Mechanical support can be provided as either temporary (usually extra-corporeal membrane oxygenation [ECMO]) or ‘permanent’ (ventricular assist device [VAD]). The patients can then be bridged on these various devices to either a decision about further management, a more permanent mechanical assist device (i.e. convert ECMO to a VAD), or to transplant. Since the introduction of third-generation devices to the Alfred’s VAD programme in 2001, 101 patients have been implanted with either VentrAssist [formerly VentraCor Ltd., now Thoratec Corp., Pleasanton CA, USA], HeartMate II [Thoratec Corp., op cit.] or Heartware HVAD [HeartWare Inc., Framingham MA, USA] third generation continuous flow devices. The aim of this project is to establish and expand our knowledge of RV failure in LVAD patients in the context of the local population. We created a database to investigate the predictors of RV failure, validate the use of existing predictive models in the local population, study the efficacy of ECMO-to-LVAD bridging and then assess the application of ‘permanent’ RVAD support in LVAD patients. We also conducted in-vitro studies to assess the optimal on-table modifications required to configure an existing LVAD (the HeartWare HVAD) for ‘off-label‘ permanent RVAD use.