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Ventricular assist devices: the rise of the machines

Session presentations
Heart Failure (HF)

Yesterday at the Heart Failure Guidelines presentation session more than half of the attendees left the room just before the lecture on surgery, so deliberately missing heart transplantation (HTx) and mechanical circulatory support (MCS). So this morning at the beginning of “Ventricular assist devices: the rise of the machines” seminar - that I chaired with Professor J Nanes from Athens, Greece, and that  I am now reporting about- I was not surprised to find only a 25% seat occupancy, and I was glad to see people coming in throughout the session. And I hope that more people will see it on the web during the next 12 months. Because undoubtedly, machines matter for heart failure cardiologists, since they matter for their patients: D. Mancini and FW Mohr estimated a population of potential candidates for a Left Ventricular Assist Device (LVAD) implantation at approximately 100 000 and 250 000 patients in the U.S. and in Europe respectively, characterized by age <75 years and advanced/refractory HF due to severe systolic LV dysfunction.
M Jessup summarized the pathway for indication and timing, with special attention to the difficult art of  prognostication: beyond some well-known multiparametric scores (Heart Failure Survival Score – ESCAPE score – Seattle HF score) she reminded us of some simple but reliable concepts: history of hospitalization, and especially of recurrent hospitalizations or hospitalization requiring inotropes, is a powerful negative prognostic marker; progressive functional limitation, i.e. being able to walk for less than 1 block, is generally associated with patient perception of the severity of his/her disease, with life expectancy of less than 1 year.

The results of VAD therapy have remarkably improved during the last 10 years, as both M Jessup and D Mancini showed: 1-year survival has increased from 50% in the REMATCH trial (which randomized patients with advanced HF, mostly inotrope-dependent, to medical therapy or a pulsatile LVAD) to more than 80% in the recently published ADVANCE trial, an observational study comparing a continuous flow centrifugal pump with the current benchmark in HTx candidates. This improvement is mainly due to evolving technology (longer survival and less complication with continuous flow versus pulsatile flow devices), and also to better patient selection and increased experience in patient management. In fact, while clinical and haemodynamic characteristics of the ADVANCE trial patients are less compromised than those of patients included in previous studies, the proportion of patients on inotropes at the time of operation (INTERMACS profile 1 to 3) is still high but overall results are similarly good in current practice in the U.S., as shown by the INTERMACS Registry data.

Reliability of the device over time is mostly important when HTx is precluded, as in the case of the so-called Destination Therapy (DT). D Mancini pointed out that although short-to-medium term (1-year) survival after LVAD implantation is approximating that observed with HTx, many complications still punctuate long-term follow-up: cerebrovascular accidents, driveline site of entry infection, gastrointestinal bleeding, and pump malfunction. Thus, the usefulness of anticipating the indication for LVAD implantation in less compromised patients (INTERMACS profile 4 to 7) must be verified, and is currently investigated in two trials (ROADMAP and REVIVE-IT). Since the availability of donor hearts is stable over time, an increasing number of patients require mechanical support while awaiting, and the proportion of patients on LVAD at the time of HTx is increasing. Meanwhile, the time spent on support is also increasing in patients implanted as bridge-to-transplant (BTT) indication, making the distinction between BTT and DT less clear.

While M Jessup and D Mancini gave us the general perspective of LVAD therapy especially for chronic severe HF, F Ruschitzka and F Mohr discussed two critical issues, i.e. the decision about short-term assistance in patients with very acute, evolving cardiogenic shock, and the management of right ventricular (RV) failure in candidates and recipients of MCS.

F Ruschitzka showed that, as frequently happens in the intensive care setting, the advantages or disadvantages of short-term circulatory support (either with intra aortic balloon pump (IABP), extra corporeal membrane oxygenation (ECMO) or other temporary devices) vs. medical therapy have not been demonstrated in randomized studies. The criteria for choosing a temporary support should take into account the etiology of the disease, the capability of the support to improve myocardial and tissue perfusion / oxygenation, and to unload the left ventricle, the expected complications, and also the center experience with the device. Besides improving end-organ function, the scope of short-term circulatory support is essentially to buy time to allow myocardial recovery, when possible, and to evaluate the feasibility and probability of success of HTx or long-term LVAD implantation.

RV failure may be a late complication in LVAD recipients, but is more common and threatening in the perioperative/early postoperative setting. F Mohr illustrated how RV failure can only partially be predicted and prevented by means of multiparametric patient evaluation and hemodynamic optimization prior to LVAD implantation. Perioperative ECMO may be useful for early transient RV dysfunction. “Old” paracorporeal assist devices and total artificial heart are difficult solutions for the long term, mainly due to the limited hemodynamic performance and to the severe impairment of quality of life. Recently, the centrifugal pump HeartWare, designed for LV support, has also been utilized for RV assistance in a few patients, with overall satisfactory preliminary results in comparison with the other available options.

In summary, as D Mancini said in her final slide, we have seen an extraordinary improvement in mechanical circulatory support therapy and, consequently, in life expectancy of the patients with advanced/refractory HF which are suitable for LVAD implantation – but we must do better. Contraindications and risk factors exist for LVAD surgery (although less than for HTx), and the postoperative course may be complicated. Thus, in my opinion we should look at this therapy with both caution and enthusiasm, we must be clear and realistic with our patients also regarding the probability of remaining on LVAD for a long time despite a BTT indication, and we must stimulate and perhaps steer technical evolution toward targets that are relevant for patient safety and quality of life. 




Ventricular assist devices: the rise of the machines

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.