Medical management of patients with continuous-flow left ventricular assist devices

Stem cell and exosome therapies for regenerating damaged myocardium in heart failure

Finding novel treatments for cardiovascular diseases (CVDs) is a hot topic in medicine; cell-based therapies have reported promising news for controlling dangerous complications of heart disease such as myocardial infarction (MI) and heart failure (HF). Various progenitor/stem cells were tested in various in-vivo, in-vitro, and clinical studies for regeneration or repairing the injured tissue in the myocardial to accelerate the healing. Fetal, adult, embryonic, and induced pluripotent stem cells (iPSC) have revealed the proper potency for cardiac tissue repair. As an essential communicator among cells, exosomes with specific contacts (proteins, lncRNAs, and miRNAs) greatly promote cardiac rehabilitation. Interestingly, stem cell-derived exosomes have more efficiency than stem cell transplantation. Therefore, stem cells induced pluripotent stem cells (iPSCs), embryonic stem cells (ESCs), cardiac stem cells (CDC), and skeletal myoblasts) and their-derived exosomes will probably be considered an alternative therapy for CVDs remedy. In addition, stem cell-derived exosomes have been used in the diagnosis/prognosis of heart diseases. In this review, we explained the advances of stem cells/exosome-based treatment, their beneficial effects, and underlying mechanisms, which will present new insights in the clinical field in the future.

Inhaled Epoprostenol Compared With Nitric Oxide for Right Ventricular Support After Major Cardiac Surgery

BACKGROUND

Right ventricular failure (RVF) is a leading driver of morbidity and death after major cardiac surgery for advanced heart failure, including orthotopic heart transplantation and left ventricular assist device implantation. Inhaled pulmonary-selective vasodilators, such as inhaled epoprostenol (iEPO) and nitric oxide (iNO), are essential therapeutics for the prevention and medical management of postoperative RVF. However, there is limited evidence from clinical trials to guide agent selection despite the significant cost considerations of iNO therapy.

METHODS

In this double-blind trial, participants were stratified by assigned surgery and key preoperative prognostic features, then randomized to continuously receive either iEPO or iNO beginning at the time of separation from cardiopulmonary bypass with the continuation of treatment into the intensive care unit stay. The primary outcome was the composite RVF rate after both operations, defined after transplantation by the initiation of mechanical circulatory support for isolated RVF, and defined after left ventricular assist device implantation by moderate or severe right heart failure according to criteria from the Interagency Registry for Mechanically Assisted Circulatory Support. An equivalence margin of 15 percentage points was prespecified for between-group RVF risk difference. Secondary postoperative outcomes were assessed for treatment differences and included: mechanical ventilation duration; hospital and intensive care unit length of stay during the index hospitalization; acute kidney injury development including renal replacement therapy initiation; and death at 30 days, 90 days, and 1 year after surgery.

RESULTS

Of 231 randomized participants who met eligibility at the time of surgery, 120 received iEPO, and 111 received iNO. Primary outcome occurred in 30 participants (25.0%) in the iEPO group and 25 participants (22.5%) in the iNO group, for a risk difference of 2.5 percentage points (two one-sided test 90% CI, -6.6% to 11.6%) in support of equivalence. There were no significant between-group differences for any of the measured postoperative secondary outcomes.

CONCLUSIONS

Among patients undergoing major cardiac surgery for advanced heart failure, inhaled pulmonary-selective vasodilator treatment using iEPO was associated with similar risks for RVF development and development of other postoperative secondary outcomes compared with treatment using iNO.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT03081052.

Cardiological Challenges Related to Long-Term Mechanical Circulatory Support for Advanced Heart Failure in Patients with Chronic Non-Ischemic Cardiomyopathy

Long-term mechanical circulatory support by a left ventricular assist device (LVAD), with or without an additional temporary or long-term right ventricular (RV) support, is a life-saving therapy for advanced heart failure (HF) refractory to pharmacological treatment, as well as for both device and surgical optimization therapies. In patients with chronic non-ischemic cardiomyopathy (NICM), timely prediction of HF's transition into its end stage, necessitating life-saving heart transplantation or long-term VAD support (as a bridge-to-transplantation or destination therapy), remains particularly challenging, given the wide range of possible etiologies, pathophysiological features, and clinical presentations of NICM. Decision-making between the necessity of an LVAD or a biventricular assist device (BVAD) is crucial because both unnecessary use of a BVAD and irreversible right ventricular (RV) failure after LVAD implantation can seriously impair patient outcomes. The pre-operative or, at the latest, intraoperative prediction of RV function after LVAD implantation is reliably possible, but necessitates integrative evaluations of many different echocardiographic, hemodynamic, clinical, and laboratory parameters. VADs create favorable conditions for the reversal of structural and functional cardiac alterations not only in acute forms of HF, but also in chronic HF. Although full cardiac recovery is rather unusual in VAD recipients with pre-implant chronic HF, the search for myocardial reverse remodelling and functional improvement is worthwhile because, for sufficiently recovered patients, weaning from VADs has proved to be feasible and capable of providing survival benefits and better quality of life even if recovery remains incomplete. This review article aimed to provide an updated theoretical and practical background for those engaged in this highly demanding and still current topic due to the continuous technical progress in the optimization of long-term VADs, as well as due to the new challenges which have emerged in conjunction with the proof of a possible myocardial recovery during long-term ventricular support up to levels which allow successful device explantation.

Analogue Mean Systemic Filling Pressure: a New Volume Management Approach During Percutaneous Left Ventricular Assist Device Therapy

The absence of an accepted gold standard to estimate volume status is an obstacle for optimal management of left ventricular assist devices (LVADs). The applicability of the analogue mean systemic filling pressure (Pmsa) as a surrogate of the mean circulatory pressure to estimate volume status for patients with LVADs has not been investigated. Variability of flows generated by the Impella CP, a temporary LVAD, should have no physiological impact on fluid status. This translational interventional ovine study demonstrated that Pmsa did not change with variable circulatory flows induced by a continuous flow LVAD (the average dynamic increase in Pmsa of 0.20 ± 0.95 mmHg from zero to maximal Impella flow was not significant (p = 0.68)), confirming applicability of the human Pmsa equation for an ovine LVAD model. The study opens new directions for future translational and human investigations of fluid management using Pmsa for patients with temporary LVADs.

Thrombus formation at the inflow cannula of continuous-flow left ventricular assist devices - a systematic analysis

BACKGROUND

Despite numerous design iterations, thrombus formation at the inflow cannula of continuous-flow left ventricular assist devices (CF-LVAD) remains an unsolved problem. We systematically investigated the impact of cannula surface on thrombus formation.

METHODS

Thrombus appearance was photographically documented in 177 explanted hearts with the polished (N=46) or sintered (N=131) inflow cannula of the HVAD. Thrombus load was compared for both inflow cannula types. Mean thrombus length was correlated with protruding cannula length. Support duration and the extent of thrombus growth were examined. The prevalence of thrombi at the left ventricular entry site and at the sintered-to-polished transition zone was correlated with left ventricular geometry and hemodynamic parameters.

RESULTS

Polished inflow cannulas showed a greater percentage and also a greater mean length of thrombus formation at the entry site than sintered cannulas (91.3% [Pol] vs. 36.7% [sTi]; p<0.0001; mean 7.6 mm vs. 1.9 mm; p<0.0001). A comparison of the early postoperative period (POD1-90) with long-term support (POD>90) showed an increase in thrombus length originating from the transition zone (1.96, ±3.41 mm vs. 3.03 ±2.91 mm; p=0.013).

CONCLUSIONS

A sintered titanium surface at the entry site is crucial to enable anchoring of myocardial tissue to the cannula. As thrombus growth progresses on polished surfaces, a greater sintered length seems to be beneficial. After an initial three-month healing period, thrombus load appears to decline during prolonged support duration at the sintered entry site but not at the transition zone.

Patient-Reported Issues Following Left Ventricular Assist Device Implantation Hospitalization

The purpose of this study was to explore the information reported by patients via a smartphone application (VAD Care App) used for left ventricular assist device (LVAD) self-care monitoring and reporting post hospital discharge. Specific aims were to examine the type and frequency of issues reported by patients through the app during months 1, 3, and 6 postdischarge. An exploratory-descriptive research design was used with 17 patients (12 males and 5 females) with durable LVADs, mean age of 48.6 ± 16 years. Data generated by the patients' daily smartphone app usage more than 6 months were extracted from the server. Data were coded and clustered according to issues reported by patients via the app and analyzed with descriptive statistics. Three clusters of issues were found: physiologic, behavioral (self-care), and signs and symptoms. LVAD flows and pulsatility indices, hypertension, driveline care, and heart failure symptoms were worse at month 1, and then appeared to improve at months 3-6. However, abnormal levels of the international normalization ratio were common at all assessment points. Further research is needed to understand the mechanism of the reported issues on treatment outcomes, then develop and test interventions to inform evidence-based practice and clinical guidelines for smartphone apps used in LVAD self-care monitoring.

Endothelial Dysfunction-related Neurological Bleeds with Continuous Flow-Left Ventricular Assist Devices Measured by Digital Thermal Monitor

Endothelial dysfunction has been demonstrated in patients with Continuous Flow-Left Ventricular Assist Devices (CF-LVADs) but association with adverse events has not been shown. We used a noninvasive, operator-independent device called VENDYS® to assess vasodilatory function based on digital thermal measurements postrelease of a brachial artery occlusion in ambulatory patients with CF-LVAD (n = 56). Aortic valve opening and pulse perception were also documented before the test. Median duration of CF-LVAD support was 438 days. The VENDYS® test generates a vascular reactivity index (VRI). Outcomes for the CF-LVAD patients were compared between VRI < 1 and VRI ≥ 1. The bleeding events were driven primarily by a difference in neurologic bleeds. Multivariate analysis showed that VRI < 1 correlated with future bleeding events (HR: 5.56; P = 0.01). The C-statistic with the VRI dichotomized as above was 0.82. There was a trend toward a worse survival in patients with poor endothelial function. Endothelial vasodilatory dysfunction measured by a simple test utilizing digital thermal monitoring can predict adverse bleeding events in patients with CF-LVADs.

Periprocedural Anticoagulation Management For Nonoperating Room Anesthesia Procedures: A Clinical Guide

Non-operating room anesthesia presents unique challenges for anesthesiologists. Limited preprocedural optimization and unfamiliarity with the location and procedure itself add to the difficulties in delivering safe care for these patients. Management of chronic oral anticoagulation can prove especially problematic since risks of bleeding for non-operating room procedures vary widely and differ from traditional surgeries. In addition, many physicians may not be familiar with the growing number of newly approved oral anticoagulants and their periprocedural management. This review will examine common non-operating procedures, their risks of bleeding, as well as pharmacokinetics of oral anticoagulants available on the market and periprocedural management options.

A Proof-of-Concept Demonstration for a Novel Soft Ventricular Assist Device

Patients treated by current ventricular assist devices (VADs) suffer from various post implantation complications including gastrointestinal bleeding and arteriovenous malformation. These issues are related to intrinsically mismatch of generated flow by VADs and the physiological flow. In addition, the common primary drawback of available VADs is excessive surgical dissection during implantation, which limits these devices to less morbid patients. We investigated an alternative soft VAD (SVAD) system that generates physiological flow, and designed to be implanted using minimally invasive surgery by leveraging soft materials. A soft VAD (which is an application of intraventricular balloon pump) is developed by utilizing a polyurethane balloon, which generates pulsatile flow by displacing volume within the left ventricle during its inflation and deflation phases. Our results show that the SVAD system generates an average ejection fraction of 50.18 ± 1.52% (n = 6 ± SD) in explanted porcine hearts. Since the SVAD is implanted via the apex of the heart, only a minithoracotomy should be required for implantation. Our results suggest that the SVAD system has the performance characteristics that could potentially make it useful for patients in acute and/or chronic heart failure, thus serving as a bridge-to-transplantation or bridge-to-recovery.

Ambulatory Ventricular Assist Device Patient Management

Understanding the ventricular assist device (VAD) patient pump interface and developing expertise in monitoring patients with a VAD are the goals of care in the ambulatory setting. The objective is to improve long-term outcomes. The purpose of expert, focused, routine outpatient surveillance is to facilitate the integration of pulseless, electrically dependent VAD patients into the community. Other goals of outpatient care include maximizing quality of life, maintaining equipment integrity, treating heart failure symptoms, monitoring for common VAD-related complications, ensuring viability as a heart transplant candidate, consideration for patients implanted to become transplantable, and monitoring for possible cardiac recovery.

HVAD Waveform Analysis as a Noninvasive Marker of Pulmonary Capillary Wedge Pressure: A First Step Toward the Development of a Smart Left Ventricular Assist Device Pump

Flow waveforms are an important feature of the HVAD left ventricular assist device (LVAD) that provides information about HVAD function and patient hemodynamics. We assessed the properties of one specific aspect of the waveform, the slope of the ventricular filling phase (VFP), and its correlation with pulmonary capillary wedge pressure (PCWP). A total of 101 screenshots from the HVAD monitor and simultaneous hemodynamic measurements were obtained simultaneously during sequential stages of invasive hemodynamic ramp studies. Each screenshot was digitized (IGOR Pro, WaveMetrics Inc., Oswego, OR) and properties of the flow waveforms including instantaneous flow and rate of change of flow were analyzed. Ventricular filling phase slope (VFPS) was calculated for each screenshot and correlated to PCWP. Ventricular filling phase slope was significantly higher in patients with PCWP ≥ 18 mm Hg than in patients with PCWP < 18 mm Hg [6.25 (5.84-7.37) L/min/s vs. 3.27 (2.00-4.69) L/min/s, p ≤ 0.0001]. A VFPS threshold of 5.8 L/min/s predicted a PCWP ≥ 18 mm Hg with a sensitivity of 87% and specificity of 95% (AUC 0.95). Ventricular filling phase slope of the HVAD flow waveform is a novel noninvasive parameter that correlates with PCWP and can discriminate elevated versus normal or low PCWP. Automated reporting of this parameter may help clinical assessment and management of patients supported by an HVAD and may serve as the basis of a smart LVAD pump that can adapt in response to changes in a patient's physiology.

Mechanical circulatory support devices as destination therapy-current evidence

Advanced heart failure is an increasing problem worldwide. Nowadays, mechanical circulatory support devices (MSCD) are an established therapeutic option for terminal heart failure after exhaustion of medical and conventional surgical treatment, and are becoming a realistic alternative to heart transplantation (HTX). There are a number of different treatment options for these patients, such as bridge to transplantation (BTT), bridge to candidacy (BTC), bridge to recovery (BTR) and the destination therapy (DT) option. The latter option has become more frequent throughout the last years, due to a donor organ shortage and an increasing number of older patients with terminal heart failure who are not eligible for HTX. These factors have led to a rapidly increasing number of LVAD implantations as well as centers which perform these procedures. This has also been due to improved LVAD survival rates and quality of life following the introduction of smaller, intrapericardial and more durable continuous flow left ventricular devices. The most common complications for these patients are device-related problems, such as coagulation disorders, gastrointestinal bleeding, device related infection, pump thrombosis or cerebrovascular accidents. However, some questions still remain unanswered or under debate, such as the exact time-point for LVAD implantation. In addition, aspects such as better biocompatibility for LVADs remain a major challenge. This review will concentrate on DT for terminal heart failure and provide an overview of the current evidence for LVAD implantation in this patient group, with particular emphasis on indication and time-point of implantation, choice of LVADs, and long term outcomes and quality of life.