Degenerative changes of the aortic valve during left ventricular assist device support

Echo and Hemodynamic-Guided Ramp Test in a Left Ventricular Assist Device Carrier With Right Ventricular Failure and Aortic Regurgitation

The clinical outcomes of patients with left ventricular assist devices (LVAD) have steadily improved, unveiling late right ventricular failure (RVF) and aortic regurgitation (AR) as drivers of long-term mortality. The continuous-flow LVAD physiology and the patient's pre-existing features predispose to these complications, recently labeled hemodynamic-related events (HDREs). We present the case of an LVAD carrier complicated by both late RVF and AR, in which a comprehensive hemodynamic and echo-guided ramp test was carried out. A step-by-step standardized ramp test protocol is described with a focus on the interpretation of longitudinal changes in hemodynamic and echocardiographic parameters at different LVAD speeds. We emphasize the clinical relevance of a dynamic evaluation to stage these complex hemodynamic scenarios and to guide individualized management. The ramp test was instrumental to unmask the relative contribution of several morphofunctional components as limiting factors to optimal hemodynamics at different LVAD speeds and identified RVF as the prevailing limiting factor, suggesting the futility of aortic valve replacement. We highlight the coexistence of AR and RVF as a hard conundrum to face, with an ominous clinical impact. An in-depth characterization of HDRE's natural history will be pivotal to build preventive and mitigation strategies to improve the durability of pump-patient continuum.

Aortic insufficiency in the patient on contemporary durable left ventricular assist device support: A state-of-the-art review on preoperative and postoperative assessment and management

The development of aortic insufficiency (AI) during HeartMate 3 durable left ventricular assist device (dLVAD) support can lead to ineffective pump output and recurrent heart failure symptoms. Progression of AI often comingles with the occurrence of other hemodynamic-related events encountered during LVAD support, including right heart failure, arrhythmias, and cardiorenal syndrome. While data on AI burdens and clinical impact are still insufficient in patients on HeartMate 3 support, moderate or worse AI occurs in approximately 8% of patients by 1 year and studies suggest AI continues to progress over time and is associated with increased frequency of right heart failure. The first line intervention for AI management is prevention, undertaking surgical intervention on the insufficient valve at the time of dLVAD implant and avoiding excessive device flows and hypertension during long-term support. Device speed augmentation may then be undertaken to try and overcome the insufficient lesion, but the progression of AI should be anticipated over the long term. Surgical or transcatheter aortic valve interventions may be considered in dLVAD patients with significant persistent AI despite medical management, but neither intervention is without risk. It is imperative that future studies of dLVAD support capture AI in clinical end-points using uniform assessment and grading of AI severity by individuals trained in AI assessment during dLVAD support.

Safety and efficacy of aortic valvuloplasty for de novo aortic insufficiency in patients with a left-ventricular assist device

OBJECTIVES

Progression of aortic insufficiency during left-ventricular assist device (LVAD) support is a crucial topic. One treatment option is aortic valvuloplasty (AVP); however, there is controversy regarding its safety and efficacy. We investigated the safety and efficacy of AVP using the coaptation stitch method (Park's stitch) performed for de novo aortic insufficiency.

METHODS

Between 2013 and 2020, 175 consecutive patients underwent LVAD implantation, of which 7 patients [men, 2 (28.6%); median age, 55 years] underwent late-stage AVP. Two patients underwent AVP within 2 weeks, and the remaining six patients underwent AVP 3, 19, 24, 28, 42, and 49 months, respectively, after LVAD implantation.

RESULTS

Preoperatively, the degree of aortic insufficiency was moderate in 6 (85.7%) patients and severe in 1 (14.3%) patient. AVP was technically successful in 6 (85.7%) patients, while one case of failed plasty was subsequently treated with bioprosthetic valve replacement. A 1-year post-AVP right heart catheterization study revealed a median pulmonary artery wedge pressure of 10.0 mmHg. No deaths or heart failure admissions occurred during the follow-up (median, 38.0 months). There was no aortic insufficiency in 2 (28.6%) patients; however, trivial AI was observed in 3 (42.8%) patients, and mild AI was observed in 1 (14.3%) patient 2 years postoperatively. However, at the 3-year follow-up, two patients developed an increase in AI grade from trivial to mild.

CONCLUSIONS

AVP using Park's stitch was safe. It is critical to carefully observe the aortic valve during AVP surgery to ensure that AVP is appropriate.

Vascular calcification and cellular signaling pathways as potential therapeutic targets

Increased vascular calcification (VC) is observed in patients with cardiovascular diseases such as atherosclerosis, diabetes, and chronic kidney disease. VC is divided into three types according to its location: intimal, medial, and valvular. Various cellular signaling pathways are associated with VC, including the Wnt, mitogen-activated protein kinase, phosphatidylinositol-3 kinase/Akt, cyclic nucleotide-dependent protein kinase, protein kinase C, calcium/calmodulin-dependent kinase II, adenosine monophosphate-activated protein kinase/mammalian target of rapamycin, Ras homologous GTPase, apoptosis, Notch, and cytokine signaling pathways. In this review, we discuss the literature concerning the key cellular signaling pathways associated with VC and their role as potential therapeutic targets. Inhibitors to these pathways represent good candidates for use as potential therapeutic agents for the prevention and treatment of VC.

Cellular and Molecular Mechanisms Activated by a Left Ventricular Assist Device

Left ventricular assist devices (LVADs) represent the final treatment for patients with end-stage heart failure (HF) not eligible for transplantation. Although LVAD design has been further improved in the last decade, their use is associated with different complications. Specifically, inflammation, fibrosis, bleeding events, right ventricular failure, and aortic valve regurgitation may occur. In addition, reverse remodeling is associated with substantial cellular and molecular changes of the failing myocardium during LVAD support with positive effects on patients' health. All these processes also lead to the identification of biomarkers identifying LVAD patients as having an augmented risk of developing associated adverse events, thus highlighting the possibility of identifying new therapeutic targets. Additionally, it has been reported that LVAD complications could cause or exacerbate a state of malnutrition, suggesting that, with an adjustment in nutrition, the general health of these patients could be improved.

Case report: A novel surgical technique for rapid valve-in-ring implantation into the native aortic annulus during left ventricular assist device implantation

The implantation of a left ventricular assist device (LVAD) has become an essential requirement for managing patients with end-stage heart failure. However, aortic valve insufficiency is a contraindication for LVAD implantation in patients with end-stage heart failure, partly because of the decreasing efficiency of mechanical circulatory support and the eventual development of right ventricular failure. Herein, we present the first case of performing transcatheter aortic valve replacement in valve-in-ring along with LVAD implantation for the treatment of a 60-year-old male suffering from refractory heart failure due to dilated cardiomyopathy and pure aortic insufficiency in need of a new aortic bioprosthesis. A balloon-expandable bioprosthetic transcatheter heart valve was implanted into a previously sewn annulus ring into the aortic root via transaortic access. Subsequently, a centrifugal-flow LVAD was implanted. Postoperatively, the patient was in New York Heart Association Functional Class (NYHA) II with 6-min walk test of 310 m. The patient has completed 6 months of follow-up with no events. This novel and feasible surgical technique reduced the cardiopulmonary bypass time and duration of surgery. Furthermore, it avoids the risk of redo sternotomy and decreases the chances of paravalvular leakage and worsening of aortic regurgitation.

Considerations of valvular heart disease in children with ventricular assist devices

Ventricular assist devices have become a valuable tool in the treatment of heart failure in children. The use of ventricular assist devices has decreased mortality in children with end-stage heart failure awaiting transplant. It is not uncommon for children with end-stage heart failure associated with cardiomyopathy or congenital heart disease to have significant systemic semilunar and atrioventricular valve regurgitation, which can impact the efficiency and efficacy of hemodynamic support provided by a ventricular assist device. Therefore, implanting clinicians should carefully assess for valve abnormalities that may need repair and impact device selection and cannulation strategy to effectively support this diverse population. The purpose of this review is to provide an overview of this important and relevant topic and to discuss strategies for managing these patients.

Correlation between aortic valve protein levels and vector flow mapping of wall shear stress and oscillatory shear index in patients supported with continuous-flow left ventricular assist devices

BACKGROUND

Continuous-flow left ventricular assist devices commonly lead to aortic regurgitation, which results in decreased pump efficiency and worsening heart failure. We hypothesized that non-physiological wall shear stress and oscillatory shear index alter the abundance of structural proteins in aortic valves of left ventricular assist device (LVAD) patients.

METHODS

Doppler images of aortic valves of patients undergoing heart transplants were obtained. Eight patients had been supported with LVADs, whereas 10 were not. Aortic valve tissue was collected and protein levels were analyzed using mass spectrometry. Echocardiographic images were analyzed and wall shear stress and oscillatory shear index were calculated. The relationship between normalized levels of individual proteins and in vivo echocardiographic measurements was evaluated.

RESULTS

Of the 57 proteins of interest, there was a strong negative correlation between levels of 15 proteins and the wall shear stress (R < -0.500, p ≤ 0.05), and a moderate negative correlation between 16 proteins and wall shear stress (R -0.500 to -0.300, p ≤ 0.05). Gene ontology analysis demonstrated clusters of proteins involved in cellular structure. Proteins negatively correlated with WSS included those with cytoskeletal, actin/myosin, cell-cell junction and extracellular functions. C: In aortic valve tissue, 31 proteins were identified involved in cellular structure and extracellular junctions with a negative correlation between their levels and wall shear stress. These findings suggest an association between the forces acting on the aortic valve (AV) and leaflet protein abundance, and may form a mechanical basis for the increased risk of aortic leaflet degeneration in LVAD patients.

Interactive contribution of hyperinsulinemia, hyperglycemia, and mammalian target of rapamycin signaling to valvular interstitial cell differentiation and matrix remodeling

Diabetes and its major key determinants insulin resistance and hyperglycemia are known risk factors for calcific aortic valve disease (CAVD). The processes leading to molecular and structural alterations of the aortic valve are yet not fully understood. In previous studies, we could show that valvular interstitial cells (VIC) display canonical elements of classical insulin signaling and develop insulin resistance upon hyperinsulinemia and hyperglycemia accompanied by impaired glucose metabolism. Analyses of cultured VIC and aortic valve tissue revealed extracellular matrix remodeling and degenerative processes. Since PI3K signaling through mammalian target of rapamycin (mTOR) is involved in fibrotic processes of the heart, we aim at further functional investigation of this particular Akt-downstream signaling pathway in the context of diabetes-induced CAVD. Primary cultures of VIC were treated with hyperinsulinemia and hyperglycemia. Phosphorylation of mTOR(Ser²⁴⁴⁸) was determined by Western blot analysis after acute insulin stimulus. Inhibition of mTOR phosphorylation was performed by rapamycin. Phosphorylation of mTOR complex 1 (MTORC1) downstream substrates 4E-BP1(Thr^37/46) and P70S6K(Thr³⁸⁹), and MTORC2 downstream substrate Akt(Ser⁴⁷³) as well as the PDK1-dependent phosphorylation of Akt(Thr³⁰⁸) was investigated. Markers for extracellular matrix remodeling, cell differentiation and degenerative changes were analyzed by Western blot analysis, semi-quantitative real-time PCR and colorimetric assays. Hyperinsulinemia and hyperglycemia lead to alterations of VIC activation, differentiation and matrix remodeling as well as to an abrogation of mTOR phosphorylation. Inhibition of mTOR signaling by rapamycin leads to a general downregulation of matrix molecules, but to an upregulation of α-smooth muscle actin expression and alkaline phosphatase activity. Comparison of expression patterns upon diabetic conditions and rapamycin treatment reveal a possible regulation of particular matrix components and key degeneration markers by MTORC1 downstream signaling. The present findings broaden the understanding of mitogenic signaling pathways in VIC triggered by hyperinsulinemia and hyperglycemia, supporting the quest for developing strategies of prevention and tailored treatment of CAVD in diabetic patients.