Long-term mechanical circulatory support: could it really have a public health impact?

Cardiovascular disease is a leading cause of death in North America and Europe, and heart failure represents a major component, affecting about 2.5% of the adult population [1, 2]. Ten percent of the heart-failure population experiences truly advanced heart failure, with limited long-term survival. For patients with New York Heart Association (NYHA) Class IV heartfailure symptoms poorly responsive to medical therapy, cardiac transplantation has dramatically improved the survival and quality of life, with a 2-year survival of 80% or more, and a median survival of >10 years [3]. Although cardiac transplantation represents the standard of care for eligible NYHA Class IV heart-failure patients, the limited availability of suitable donor hearts has restricted its application to about 2500 patients annually in North America and 99% of left ventricular assist devices (LVADs) implanted in the USA have employed CF technology [6]. In 2012 alone, nearly 2500 CF pumps were implanted in the USA, essentially equalling the total number of heart transplants [7]. The dramatic increment in survival with CF pumps compared with pulsatile systems is reflected in the US INTERMACS experience since 2006 (Fig. 1). The 1- and 2-year survivals in the current era approach 80 and 70%, respectively. Of course, the majority of these pumps are currently implanted as BTT and therefore, do not directly expand the surgical support/ replacement options for end-stage heart failure. The spectrum of intended use of MCS is perhaps more easily examined in the USA than Europe because of the US regulatory requirement (possibly a disadvantage to clinicians) to commit to a strategy of either longterm permanent LVAD support (DT) or BTT at the time of implant. The approval of a CF pump for DT in the US set the stage for an increased surgical impact on advanced heart failure over that of heart transplantation alone. Between 2006 and 2011, DT implants represented only 18% of total LVAD implants in the USA; but in 2012, over 40% of implants were DT! [7] The artificiality of such designations is highlighted by the spectrum of ‘commitment’ to transplantation among centers/physicians implanting ventricular assist devices (VADs) for BTT over the past 4 years in the USA. Table 1 depicts the varying levels of commitment to transplant under the general category of BTT [7];so much so that at otally‘unofficial’ category of bridge to candidacy has emerged as a new part of the strategy repertoire. Even more indicative of the fluid nature of these designations is the movement of patients from one category to another as time elapses since implant, consistent with the well-known tendency for comorbidities to be modified by the haemodynamic impact of the VAD itself [5]. The platform for the expansion of long-term MCS is currently limited by the requirement for such patients in the USA to be transplant ineligible, a stipulation appropriate for a technology whose mid-term survival has never been competitive with cardiac transplantation. Recently, however, the door for including transplant-eligible patients has at least been unlocked, if not yet actually opened. Analyses from INTERMACS have identified patient subsets within the current DT population (generally poorer risk patients who have contraindications to transplantation) whose survival is 80% at 2 years, representing about 20% of non-urgent DT implants [8].