Benefits of Neurohormonal Therapy in Patients With Continuous-Flow Left Ventricular Assist Devices

Current and future options for adult biventricular assistance: a review of literature

In cardiogenic shock various short-term mechanical assistances may be employed, including an Extra Corporeal Membrane Oxygenator and other non-dischargeable devices. Once hemodynamic stabilization is achieved and the patient evolves towards a persisting biventricular dysfunction or an underlying long-standing end-stage disease is present, aside from Orthotopic Heart Transplantation, a limited number of long-term therapeutic options may be offered. So far, only the Syncardia Total Artificial Heart and the Berlin Heart EXCOR (which is not approved for adult use in the United States unlike in Europe) are available for extensive implantation. In addition to this, the strategy providing two continuous-flow Left Ventricular Assist Devices is still off-label despite its widespread use. Nevertheless, every solution ensures at best a 70% survival rate (reflecting both the severity of the condition and the limits of mechanical support) with patients suffering from heavy complications and a poor quality of life. The aim of the present paper is to summarize the features, implantation techniques, and results of current devices used for adult Biventricular Mechanical Circulatory Support, as well as a glance to future options.

Physiology of Continuous-Flow Left Ventricular Assist Device Therapy

The expanding use of continuous-flow left ventricular assist devices (CF-LVADs) for end-stage heart failure warrants familiarity with the physiologic interaction of the device with the native circulation. Contemporary devices utilize predominantly centrifugal flow and, to a lesser extent, axial flow rotors that vary with respect to their intrinsic flow characteristics. Flow can be manipulated with adjustments to preload and afterload as in the native heart, and ascertainment of the predicted effects is provided by differential pressure-flow (H-Q) curves or loops. Valvular heart disease, especially aortic regurgitation, may significantly affect adequacy of mechanical support. In contrast, atrioventricular and ventriculoventricular timing is of less certain significance. Although beneficial effects of device therapy are typically seen due to enhanced distal perfusion, unloading of the left ventricle and atrium, and amelioration of secondary pulmonary hypertension, negative effects of CF-LVAD therapy on right ventricular filling and function, through right-sided loading and septal interaction, can make optimization challenging. Additionally, a lack of pulsatile energy provided by CF-LVAD therapy has physiologic consequences for end-organ function and may be responsible for a series of adverse effects. Rheological effects of intravascular pumps, especially shear stress exposure, result in platelet activation and hemolysis, which may result in both thrombotic and hemorrhagic consequences. Development of novel solutions for untoward device-circulatory interactions will facilitate hemodynamic support while mitigating adverse events. © 2021 American Physiological Society. Compr Physiol 12:1-37, 2021.

Left Ventricular Assist Device: Indication, Timing, and Management

Left ventricular assist devices (LVADs) are indicated in inotrope-dependent heart failure (HF) patients with pure or predominant LV dysfunction. Survival benefit is less clear in ambulatory, advanced HF. Timing is crucial: early, unnecessary exposure to the risks of surgery, and device-related complications (infections, stroke, and bleeding) should be weighed against the probability of dying or developing irreversible right ventricular and/or end-organ dysfunction while deferring implant. The interplay between LVAD and heart transplantation depends largely on donor availability and allocation rules. Postoperatively, quality of life depends on patients' expectations and is influenced by complications. Patients' preferences, prognosis, and alternative options-including palliation-should be openly discussed and reviewed before and after the operation.

The role of renin-angiotensin system in patients with left ventricular assist devices

End-stage heart failure is a condition in which the up-regulation of the systemic and local renin-angiotensin-aldosterone system (RAAS) leads to end-organ damage and is largely irreversible despite optimal medication. Left ventricular assist devices (LVADs) can downregulate RAAS activation by unloading the left ventricle and increasing the cardiac output translating into a better end-organ perfusion improving survival. However, the absence of pulsatility brought about by continuous-flow devices may variably trigger RAAS activation depending on left ventricular (LV) intrinsic contractility, the design and speed of the pump device. Moreover, the concept of myocardial recovery is being tested in clinical trials and in this setting LVAD support combined with intense RAAS inhibition can promote recovery and ensure maintenance of LV function after explantation. Blood pressure control on LVAD recipients is key to avoiding complications as gastrointestinal bleeding, pump thrombosis and stroke. Furthermore, emerging data highlight the role of RAAS antagonists as prevention of arteriovenous malformations that lead to gastrointestinal bleeds. Future studies should focus on the role of angiotensin receptor inhibitors in preventing myocardial fibrosis in patients with LVADs and examine in greater details the target blood pressure for these patients.

A reappraisal of the pharmacologic management of gastrointestinal bleeding in patients with continuous flow left ventricular assist devices

Advancements in the design and functionality of continuous flow left ventricular assist devices (CF-LVADs), as well as a limited number of donor hearts, have resulted in an increased utilization of this therapy among advanced heart failure (HF) patients. Despite these advancements, gastrointestinal bleeding (GIB) remains a common complication after CF-LVAD implantation. The mechanism of GIB in these patients is complex and includes a combination of angiodysplasia, platelet dysfunction, acquired von Willebrand disease, and a variety of patient-specific factors including advanced age and history of GIB. Several pharmacotherapy options have been reported in the literature, though studies supporting the use of these agents are often small, retrospective reports. Within this review, we discuss the various pharmacologic agents, their proposed mechanisms of action, and the available literature pertaining to their effectiveness and tolerability. Additionally, we propose an evidence-based treatment algorithm, encompassing the updated literature, cost of therapy, medication side effects, and ease of administration.