Left ventricular assist devices: A historical perspective at the intersection of medicine and engineering

Abstract

Over the last half‐century, left ventricular assist device (LVAD) technology has progressed from conceptual therapy for failed cardiopulmonary bypass weaning to an accepted destination therapy for advanced heart failure. The history of LVAD engineering is defined by an initial development phase, which demonstrated the feasibility of such an approach, to the more recent three major generations of commercial devices. In this review, we explore the engineering challenges of LVADs, how they were addressed over time, and the clinical outcomes that resulted from each major technological development. The first generation of commercial LVADs were pulsatile devices, which lacked the appropriate durability due to their number of moving components and hemocompatibility. The second generation of LVADs was defined by replacement of complex, pulsatile pumps with primarily axial, continuous‐flow systems with an impeller in the blood passageway. These devices experienced significant commercial success, but the presence of excessive trauma to the blood and in‐situ bearing resulted in an unacceptable burden of adverse events. Third generation centrifugal‐flow pumps use magnetically suspended rotors within the pump chamber. Superior outcomes with this newest generation of devices have been observed, particularly with respect to hemocompatibility‐related adverse events including pump thrombosis, with fully magnetically levitated devices. The future of LVAD engineering includes wireless charging foregoing percutaneous drivelines and more advanced pump control mechanisms, including synchronization of the pump flow with the native cardiac cycle, and varying pump output based on degree of physical exertion using sensor or advanced device‐level data triggers.

A Historical Review of Mechanical Circulatory Support

“…These early devices were used to support patients as a BTT and could be used as left-, right-, and biventricular devices (LVAD, RVAD, and BiVAD). The first-generation devices introduced electromechanical actuation, which allowed some to be powered by a battery worn on the waist, affording better mobility, and allowing patients to be discharged from the hospital waiting for a new heart [20]. Anecdotally, these first devices had several disadvantages including large size, noise emission, infectious diseases, malfunctioning, mechanical tears, or valve degradation.…”

“…First-generation LVADs were known as volume displacement pumps and generated flow via a pulse generator [15,21]. The goal of the first-generation LVADs was to provide long-term circulatory support, such that these devices could be used as a bridge to transplant [20,22].…”

“…A sintered titanium microsphere layer was applied to the titanium blood-contacting surfaces of the pump and a fibrillar texture was on the polyurethane diaphragm. These surface modifications allowed circulating cells to adhere and form an intimalike tissue layer [20,22]. The HeartMate IP (Abbott Laboratories, formerly Thoratec, Pleasanton, CA, USA) was the first LVAD to receive FDA approval for use in patients as a BTT in 1994.…”

“…The second-and third-generation VADs replace or support only the ventricular function. There is no direct attempt made to imitate the modality of the native, ventricular function [20,34].…”

“…In 2001, Thoratec introduced the most successful LVAD, with respect to implantation numbers and studies, the HeartMate II VAD which was smaller and lighter than the original HeartMate XVE [3] (Figure 2). The development was initiated in [20,34]. It was approved for use in 2005 in Europe and the USA, the FDA approved it as a BTT device in 2008 and as a DT device in 2010.…”