Aortic Hemodynamics of Spiral-Flow-Generated Mechanical Assistance.

Background: Mechanical circulatory support devices are being increasingly used as destination therapy in end-stage heart failure patients. Although current devices have significantly improved survival rates, the resulting hemodynamics remains nonphysiological. Spiral forms of blood flow are known to exist in the large arteries (eg, aorta) and serve as a biomimetic-motivation for generating these physiologically adapted flow regimes.

The mechanics of spiral flow: Enhanced washout and transport.

Spiral/helical forms of blood flow have been observed in large arteries of the cardiovascular system, but their benefits remain underappreciated. Spiral flow has been postulated to improve near-wall washout, promoting anti-atherothrombotic conditions. This research aims to study the washout characteristics of spiral flow, specifically, its ability to increase velocity and wall shear stress (WSS) in atherothrombotic-prone regions.

Dual Defibrillation is Highly Variable: An Analysis of Pulse Interval Delivered in Dual Defibrillation.

Dual defibrillation (DD) is a technique where two external defibrillators are applied with two different pad configurations and discharged to treat refractory ventricular fibrillation (RVF). Although commonly called dual sequential defibrillation (DSD), if the delivered electrical pulses overlap with no pulse interval, the shocks are actually dual simultaneous defibrillation (DSiD). Manual DD technique is not standardized and the effect that the method of activation has on the delivered pulse interval has never been studied.

Circulatory Mechanotherapeutics: Moving with the Force.

Purpose Of Review: This review describes the current state of advancements in mechanical circulatory support (MCS) devices with significantly improved hemodynamic performance and decreased adverse events. Novel considerations for future MCS designs that impart spiral flow regimes will be detailed.

Recent Findings: Significant challenges in MCS device use have included size reduction, premature pump mechanical bearing failure, acquired bleeding disorders, and vascular complications related to high shear forces and jetting.

Vortical flow characteristics of mechanical cavopulmonary assistance: Pre- and post-swirl dynamics.

Surgical optimization of the cavopulmonary connection and pharmacological therapy for dysfunctional Fontan physiology continue to advance, but these treatment approaches only slow the progression of decline to end-stage heart failure. The development of a mechanical cavopulmonary assist device will provide a viable therapeutic option in the bridging of patients to transplant or to stabilization. We hypothesize that rotational blood flow, delivered by an implantable axial flow blood pump, could effectively assist the venous circulation in Fontan patients by mimicking vortical blood flow patterns in the cardiovascular system.

Ultrasound-induced modulation of cardiac rhythm in neonatal rat ventricular cardiomyocytes.

Isolated neonatal rat ventricular cardiomyocytes were used to study the influence of ultrasound on the chronotropic response in a tissue culture model. The beat frequency of the cells, varying from 40 to 90 beats/min, was measured based upon the translocation of the nuclear membrane captured by a high-speed camera. Ultrasound pulses (frequency = 2.

Mechanically stimulated contraction of engineered cardiac constructs using a microcantilever.

The beating heart undergoes cyclic mechanical and electrical activity during systole and diastole. The interaction between mechanical stimulation and propagation of the depolarization wavefront is important for understanding not just normal sinus rhythm, but also mechanically induced cardiac arrhythmia. This study presents a new platform to study mechanoelectrical coupling in a 3-D in vitro model of the myocardium.

Augmentation of integrin-mediated mechanotransduction by hyaluronic acid.

Changes in tissue and organ stiffness occur during development and are frequently symptoms of disease. Many cell types respond to the stiffness of substrates and neighboring cells in vitro and most cell types increase adherent area on stiffer substrates that are coated with ligands for integrins or cadherins. In vivo cells engage their extracellular matrix (ECM) by multiple mechanosensitive adhesion complexes and other surface receptors that potentially modify the mechanical signals transduced at the cell/ECM interface.

α-Catenin localization and sarcomere self-organization on N-cadherin adhesive patterns are myocyte contractility driven.

The N-cadherin (N-cad) complex plays a crucial role in cardiac cell structure and function. Cadherins are adhesion proteins linking adjacent cardiac cells and, like integrin adhesions, are sensitive to force transmission. Forces through these adhesions are capable of eliciting structural and functional changes in myocytes.

Reprogramming cardiomyocyte mechanosensing by crosstalk between integrins and hyaluronic acid receptors.

The elastic modulus of bioengineered materials has a strong influence on the phenotype of many cells including cardiomyocytes. On polyacrylamide (PAA) gels that are laminated with ligands for integrins, cardiac myocytes develop well organized sarcomeres only when cultured on substrates with elastic moduli in the range 10 kPa-30 kPa, near those of the healthy tissue. On stiffer substrates (>60 kPa) approximating the damaged heart, myocytes form stress fiber-like filament bundles but lack organized sarcomeres or an elongated shape.

Intercellular and extracellular mechanotransduction in cardiac myocytes.

Adult cardiomyocytes are terminally differentiated with minimal replicative capacity. Therefore, long-term preservation or enhancement of cardiac function depends on structural adaptation. Myocytes interact with the extracellular matrix, fibroblasts, and vascular cells and with each other (end to end; side to side).

Cardiac myocyte remodeling mediated by N-cadherin-dependent mechanosensing.

Cell-to-cell adhesions are crucial in maintaining the structural and functional integrity of cardiac cells. Little is known about the mechanosensitivity and mechanotransduction of cell-to-cell interactions. Most studies of cardiac mechanotransduction and myofibrillogenesis have focused on cell-extracellular matrix (ECM)-specific interactions.

Pacing-induced cardiac gap junction remodeling: modulation of connexin43 phosphorylation state.

Background: Altered myocardial distribution of gap junctions and intercellular coupling have been implicated in nonuniform conduction of the depolarization wave and repolarization asynchrony in the mammalian heart. We tested the hypothesis that short-term cardiac pacing is associated with structural remodeling of gap junctions and their altered spatial distribution in cardiac myocytes in the immediate vicinity of the pacing site.

Materials And Methods: Isolated adult male rat hearts (n = 8) were perfused using a Langendorff apparatus.

A hierarchical algorithm for calculating the isotopic fine structures of molecules.

This article presents a memory efficient algorithm for accurately calculating the isotopic fine structures of molecules. Treating individual isotopic species of a molecule as different mass states, we introduce the concept of transitions between mass states and represent all mass states of the molecule in a hierarchical structure. We show that there exists a simple relationship between two different mass states at two different levels of the hierarchical structure.

Anti- and pro-arrhythmic effects of cardiac resynchronization therapy: point of view.

Cardiac resynchronization therapy (CRT) in patients with heart failure and bundle branch block (BBB) improves regional muscle mechanics and mechanical pump function of the heart. In addition, modulation of wall motion timing and contraction can exert an antiarrhythmic effect, reducing the potential of sudden cardiac death. This effect of CRT could also be attributed to the improvement in excitation-contraction coupling, mechanical synchronization, and improved myocardial perfusion.

Comparison of eight prosthetic aortic valves in a cadaver model.

Objectives: Proper valve selection is critical to ensure appropriate valve replacement for patients, because implantation of a small valve might place the patient at risk for persistent gradients. Labeled valve size is not the same as millimeter measure of prosthetic valve diameters or the annulus into which it will fit. Studies that use the labeled valve size in lieu of actual measured diameter in millimeters to compare different valves might be misleading.

Real-time monitoring of adhesion and aggregation of platelets using thickness shear mode (TSM) sensor.

Hemostasis is required to maintain vascular system integrity, but thrombosis, formation of a clot in a blood vessel, is one of the largest causes of morbidity and mortality in the industrialized world. Novel clinical and research tools for characterizing the hemostatic system are of continued interest, and the object of this research is to test the hypothesis that clinically relevant platelet function can be monitored using an electromechanical sensor. A piezoelectric thickness shear mode (TSM) biosensor coated with collagen-I fibers to promote platelet activation and adhesion was developed and tested for sensitivity to detect these primary events.

Using heart rate variability to stratify risk of obstetric patients undergoing spinal anesthesia.

In this study, we evaluated whether point correlation dimension (PD2), a measure of heart rate variability, can predict hypotension accompanying spinal anesthesia for cesarean delivery. After the administration of spinal anesthesia with bupivacaine, hypotension was defined as systolic blood pressure View Article and Find Full Text PDF

Cardiomyocyte-mediated contact programs human mesenchymal stem cells to express cardiogenic phenotype.

Background: Intercellular crosstalk and cellular plasticity are key factors in embryogenesis and organogenesis. The microenvironment plays a critical role in directing the progression of stem cells into differentiated cells. We hypothesized that intercellular interaction between adult human mesenchymal stem cells and adult human cardiomyocytes would induce stem cells to acquire the phenotypical characteristics of cardiomyocytes, and we tested the role that direct cell-to-cell contact plays in directing this differentiation process.

Physiologic and hemodynamic basis of ventricular assist devices.

Heart failure is a particularly complex disorder with etiology that is primary in nature or secondary to other systemic diseases, including hypertension, diabetes, and atherosclerosis. The pathogenesis appears to result, in part, from extensive abnormal interactions among tissues, such as the heart, vasculature, kidney, lungs, and sympathetic nervous system. Improvements in understanding this complex disorder, particularly factors that contribute to cardiac cell cycle alterations, gene activation and re-expression resulting in cardiac remodeling and, eventually, maladaption are paramount.

Early detection of acute allograft rejection by linear and nonlinear analysis of heart rate variability.

Objective: The first months after orthotopic heart transplantation are associated with the highest risk of acute allograft rejection. This study explores the utility and reliability of linear and novel nonlinear metrics of heart rate variability as predictors of graft rejection. The underlying hypothesis is that the transplanted heart, in response to inflammatory mediators, alters the dynamic properties of its rhythm-generating system.