Advances in Continuous Flow Left Ventricular Assist Device Support for End-Stage Heart Failure: A Therapy in Evolution

A Novel Control Method for Rotary Blood Pumps as Left Ventricular Assist Device Utilizing Aortic Valve State Detection

A novel control method for rotary blood pumps is proposed relying on two different objectives: regulation of pump flow in accordance with desired value and the maintenance of partial support with an open aortic valve by the variation of pump speed. The estimation of pump flow and detection of aortic valve state was performed with mathematical models describing the first- and second generation of Sputnik rotary blood pumps. The control method was validated using a cardiovascular system model. The state of the aortic valve was detected with a mean accuracy of 91% for Sputnik 1 and 96.2% for Sputnik 2 when contractility, heart rate, and systemic vascular resistance was changed. In silico results for both pumps showed that the proposed control method can achieve the desired pump flow level and maintain the open state of the aortic valve by periodically switching between two objectives under contractility, heart rate, and systemic vascular resistance changes. The proposed method showed its potential for safe operation without adverse events and for the improvement of chances for myocardial recovery.

Novel Formula to Calculate Three-Dimensional Angle Between Inflow Cannula and Device Body of HeartMate II LVAD

BACKGROUND

The acute angle between inflow cannula and device body of HeartMate II left ventricular assist device (LVAD) (Abbott, Pleasanton, California) is associated with device thrombosis. However, most studies utilized two-dimensional (2D) angle obtained from chest roentgenogram (CXR), which is unlikely accurate. We aimed to create and validate a formula to estimate actual three-dimensional (3D) angle.

METHODS

We retrospectively reviewed the cohort undergoing HeartMate II LVAD implantation between 2008 and 2016. A formula for calculating 3D angles of the LVAD inflow cannula relative to the device body was mathematically derived, using simple 2D measurements from CXR.

RESULTS

The cohort included consecutive 275 patients with HeartMate II (median age: 60 [25% quartile: 51, 75% quartile: 68] years). There was no significant difference between the calculated 3D angles (from formula) and actual 3D angles (from computed tomography) from the subset group with 3D computed tomography (n = 28) (71.7° ± 13.4° vs 71.1° ± 11.5°, P = .858). Among all participants, the calculated 3D angle (from formula) was 74.4° ± 14.2°, which was significantly larger than the 2D projected angle (from CXR) (65.2° ± 11.3°, P < .001). There was no statistical difference in the calculated 3D angles (from formula) between patients with/without device thrombosis, hemorrhagic stroke, ischemic stroke, or mortality (P > .05 for all).

CONCLUSIONS

We established a novel formula to mathematically calculate actual 3D angles between inflow cannula and device body of HeartMate II. The formula would help investigators to validate their findings of the relationship between 2D projected angle (from CXR) and device thrombosis.

When Should the Electrophysiologist Be Involved in Managing Patients with Ventricular Assist Devices and Ventricular Arrhythmias?

The successful management of ventricular arrhythmias (VAs) in people with left ventricular assist devices (LVADs) is often complex. The need for and the role of defibrillator therapy is continually evolving in this group. VAs occur frequently and significantly impact the clinical course of patients with LVADs. The management of VAs begins prior to LVAD implantation and typically involves appropriate implantable cardioverter-defibrillator use and programming after the fact. Surgical ablation during LVAD implantation and supplementary catheter ablation performed as needed are attractive options for the management of VAs in this population. The performance of catheter ablation is generally safe and feasible after LVAD implantation with a team approach.

Sex-Specific Outcome Disparities in Patients Receiving Continuous-Flow Left Ventricular Assist Devices: A Systematic Review and Meta-analysis

Continuous-flow left ventricular assist devices (CF-LVADs) decrease mortality and improve quality of life in patients with advanced heart failure (HF). Their widespread utilization has led to concerns regarding increased adverse effects, especially in women. Nevertheless, sex-specific data remain limited. We searched Medline, Embase, Scopus, and the Cochrane Library for publications reporting sex-specific outcomes after CF-LVADs from January 2008 through January 2017. Outcomes were compared under the random-effects model and heterogeneity examined via χ test and I statistics. A total of 10 studies including 4,493 CF-LVAD recipients were included in the analysis (23.5% women). The overall rate of stroke was significantly higher in women (odds ratio [OR] 1.94; 95% confidence interval [CI] 1.32-2.84; p = 0.0007). This was true for ischemic strokes (OR 2.03; 95% CI 1.21-3.42; p = 0.008) and hemorrhagic strokes (OR 2.03; 95% CI 1.21-3.42; p = 0.008). Women were also more likely to develop right HF necessitating right ventricular assist device (RVAD) implantation (OR 2.12; 95% CI 1.08-4.15; p = 0.03). Other adverse events including renal failure, bleeding, and device-related infection were comparable for both genders. The overall mortality while on CF-LVAD was similar in both groups (OR 1.05; 95% CI 0.81-1.36; p = 0.71). Our analysis suggests that women are at greater risk of significant complications such as cerebrovascular events and right HF necessitating RVAD after CF-LVAD implantation. Further research is needed to better understand the mechanisms underlying these sex-specific outcome disparities.

Radiographic Review of Current Therapeutic and Monitoring Devices in the Chest

Chest radiographs are obtained as a standard part of clinical care. Rapid advancements in medical technology have resulted in a myriad of new medical devices, and familiarity with their imaging appearance is a critical yet increasingly difficult endeavor. Many modern thoracic medical devices are new renditions of old designs and are often smaller than older versions. In addition, multiple device designs serving the same purpose may have varying morphologies and positions within the chest. The radiologist must be able to recognize and correctly identify the proper positioning of state-of-the-art medical devices and identify any potential complications that could impact patient care and management. To familiarize radiologists with the arsenal of newer thoracic medical devices, this review describes the indications, radiologic appearance, complications, and magnetic resonance imaging safety of each device. ^©RSNA, 2018.

Effects of pump speed changes on exercise capacity in patients supported with a left ventricular assist device-an overview

The implantation of left ventricular assist devices (LVAD) has been established as a successful treatment for terminal heart failure (HF) for many years. Patient benefits include significantly improved survival, as well as improved quality of life. However, peak exercise capacity following LVAD implantation remains considerably restricted. This could be due to the predominate use of continuous-flow pumps, which operate at a fixed rotational speed and do not adapt to exercise conditions. Therefore, current research is focused on whether, and to what extent, adaptations in pump speed can influence and improve patient exercise capacity. We performed a systematic PubMed literature search on this topic, and found 11 relevant studies with 161 patients. Exercise time, peak work load, total cardiac output (TCO), peak oxygen consumption (peak VO₂) and, if available, values at the anaerobic threshold (AT) were all taken into consideration. Possible complications were documented. This paper aims to compare the results from these studies in order to discuss the effects of pump speed adaptations on exercise capacity.

Left ventricular assist device-induced reverse remodeling: it's not just about myocardial recovery

INTRODUCTION

The abnormal structure, function and molecular makeup of dilated cardiomyopathic hearts can be partially normalized in patients supported by a left ventricular assist device (LVAD), a process called reverse remodeling. This leads to recovery of function in many patients, though the rate of full recovery is low and in many cases is temporary, leading to the concept of heart failure remission, rather than recovery. Areas covered: We summarize data indicative of ventricular reverse remodeling, recovery and remission during LVAD support. These terms were used in searches performed in Pubmed. Duplication of topics covered in depth in prior review articles were avoided. Expert commentary: Although most patients undergoing mechanical circulatory support (MCS) show a significant degree of reverse remodeling, very few exhibit sufficiently improved function to justify device explantation, and many from whom LVADs have been explanted have relapsed back to the original heart failure phenotype. Future research has the potential to clarify the ideal combination of pharmacological, cell, gene, and mechanical therapies that would maximize recovery of function which has the potential to improve exercise tolerance of patients while on support, and to achieve a higher degree of myocardial recovery that is more likely to persist after device removal.