Mechanical Circulatory Support in the New Era: An Overview

Kiran Shekar; Shaun D. Gregory; John F. Fraser

Disclosures

Crit Care. 2016;20(66) 

In This Article

Background

Maximal medical therapy can no longer be seen as a justifiable end-point for refractory circulatory shock, at least in well-resourced health settings. Despite improvements in almost all other areas of cardiac and intensive care medicine, refractory cardiogenic shock, defined as cardiac and circulatory failure resulting in organ hypoperfusion,[1] continues to have unacceptably high mortality and morbidity from the resultant multiple organ failure. Whilst primary cardiac pathology remains the leading cause of cardiogenic shock, acute cardiomyopathies secondary to conditions such as sepsis and toxic ingestion are not uncommon.[2] The conventional approach to supporting patients with circulatory shock includes reversal of underlying causes when feasible, mechanical ventilation, pharmacological hemodynamic support with or without intra-aortic balloon counter pulsation, renal replacement and other supportive therapy. Whilst mechanical circulatory support (MCS) has always been an attractive option when conventional approaches fail, technological limitations, suboptimal clinical application of available technology and resource limitations have all conspired against its more widespread use.

Recently, there is increasing application of extracorporeal membrane oxygenation (ECMO) technology to provide MCS in an incremental fashion either as peripheral or central venoarterial (VA)-ECMO or as univentricular or biventricular assist devices.[3,4] The use of ECMO in cardiopulmonary resuscitation (CPR) is also expanding with experienced centers reporting favorable outcomes.[5] Other minimally invasive percutaneous ventricular assist devices (pVADs) have also been used in acute settings. Similarly, the implantable, durable, rotary blood pump-driven VADs have revolutionized the care of patients with chronic heart failure or those with acute heart failure who initially need to be stabilized on temporary MCS, and in whom cardiac recovery does not occur.[6] Although total artificial hearts have been used only sparsely, it is expected that their use will increase with the increasing heart failure population and rapid improvements in technology that are currently occurring.[7]

In an appropriately aged critically ill patient with no absolute contraindications who is failing medical therapy for circulatory shock, especially of cardiac origin, temporary MCS strategies can now be effectively utilized as a bridge to decision, to recovery, to long-term support devices (such as VADs or total artificial hearts) and/or heart transplantation in an appropriately resourced setting. Such undertakings are resource-intensive and the risk/benefit profile of these therapies and costs are already becoming more favorable. Improved and refined technological advancements, more appropriate selection of patients and better clinical use of these devices will likewise continue.

Bridging a patient from emergent temporary MCS to long term devices and/or heart transplant is a complex multidisciplinary exercise. The choice of the initial rescue MCS strategy has significant bearing not only on limiting further iatrogenic harm in the acute setting, but also on planning long-term strategies in the absence of myocardial recovery. Most of these applications have a steep learning curve and careful planning of perfusion strategies and vascular access in a time-critical situation may be challenging. Developing predetermined institutional pathways is critical to success of such MCS programs. It should be recognized that technology has evolved sufficiently and many MCS strategies are now ready for full clinical utilization, though large multicenter trials are still lacking in many areas. Such resource intensive extraordinary therapies raise several questions in relation to resource utilization, ethics, governance, quality assurance and benchmarking, all of which need to be addressed proactively. Although evidence in this area is difficult to generate, collaboration between global centers, establishment of global registries and clinical and science research networks can facilitate the volume and quality of data needed to further augment the clinician's knowledge of when and where these technologies could and should be used. A case vignette will be used to expand on the possibilities, the problems and the pathologies that can be treated with MCS.

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