Cardiovascular autonomic control in patients undergoing left ventricular assist device (LVAD) support and pharmacologic therapy

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.

Machine learning, artificial intelligence and mechanical circulatory support: A primer for clinicians

Artificial intelligence (AI) refers to the ability of machines to perform intelligent tasks, and machine learning (ML) is a subset of AI describing the ability of machines to learn independently and make accurate predictions. The application of AI combined with "big data" from the electronic health records, is poised to impact how we take care of patients. In recent years, an expanding body of literature has been published using ML in cardiovascular health care, including mechanical circulatory support (MCS). This primer article provides an overview for clinicians on relevant concepts of ML and AI, reviews predictive modeling concepts in ML and provides contextual reference to how AI is being adapted in the field of MCS. Lastly, it explains how these methods could be incorporated in the practices of medicine to improve patient outcomes.

A Case of Abulia From Left Middle Cerebral Artery Stroke in an Adolescent Treated Successfully With Short Duration Olanzapine

INTRODUCTION

Abulia is defined as a pathological state of amotivation, apathy, and global absence of willpower. It presents with a challenging array of overlapping symptoms, making effective identification and treatment difficult.

CASE PRESENTATION

We describe the first known report of an adolescent with a ventricular assist device who developed abulia following a left middle cerebral artery (MCA) stroke who responded successfully to treatment with olanzapine.

DISCUSSION

The neurobiological etiology of abulia is still unclear but is postulated to be related to deficits in the dopaminergic reward circuitry in the frontal-subcortical-mesolimbic regions. There have been reports of poststroke patients with abulia being treated by modulating this dopamine circuitry and in some cases with short-term low-dose olanzapine.

CONCLUSION

Further research is needed to develop a better understanding of the pathophysiology of abulia leading to more effective treatment algorithms including more specific diagnostic tools and effective pharmacological interventions.

Orthostatic Hypotension in Patients With Left Ventricular Assist Devices: Acquired Autonomic Dysfunction

Contemporary left ventricular assist device (LVAD) technology uses nonphysiologic continuous flow to deliver blood into the circulation. This results in a reduction of pulsatility, which is implicated in some of the commonly associated side effects with LVAD therapy, including hypertension and gastrointestinal arterial-venous malformation with related bleeding. A less frequently observed side effect is orthostatic hypotension (OH) in patients supported with LVAD therapy. We present three cases of OH in patients with LVAD, followed by a discussion on how LVAD therapy may induce autonomic dysfunction.