Is Implantation of a Left Ventricular Assist Device in Patients With Critical or Impending Cardiogenic Shock an Absolute Contraindication? Looking Back at Our Past Experience Trying to Identify Contraindicative Risk Factors

Poor survival has been demonstrated after ventricular assist device (VAD) implantation for Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) profile 1 and 2 patients compared with more stable levels. However, risk factors within this high‐risk cohort have not been determined so far. The aim of the present study was to identify risk factors associated with this very high mortality rate. Between February 1993 and January 2013, 298 patients underwent VAD implantation in our institution. One hundred nine patients were in INTERMACS level 1 and 49 patients were in INTERMACS level 2 and were therefore defined as hemodynamically critical (overall 158 patients). Assist devices implanted were: HVAD HeartWare n = 18; Incor n = 11; VentrAssist n = 2; DeBakey n = 22; and pulsatile systems n = 105. After cumulative support duration of 815.35 months, Kaplan–Meier analysis revealed a survival of 63.9, 48.8, and 40.3% at 1, 6, and 12 months, respectively. Cox regression analyses identified age > 50 (P = 0.001, odds ratio [OR] 2.48), white blood cell count > 13.000/μL (P = 0.01, OR 2.06), preoperative renal replacement therapy (P = 0.001, OR 2.63), and postcardiotomy failure (P < 0.001, OR 2.79) as independent predictors of mortality. Of note, last generation VADs were not associated with significantly better 6‐month survival (P = 0.59). Patients without the aforementioned risk factors could yield a survival of 79.2% at 6 months. This single‐center experience shows that VAD implantation in hemodynamically unstable patients generally results in poor early outcome, even in third‐generation pumps. However, avoiding the aforementioned risk factors could result in improved outcome.     

Age-related changes in neuroendocrine rhythmic function in the rhesus macaque

Many environmental conditions show rhythmic changes across the 24-h day; these include changes in light intensity, ambient temperature, food availability, and presence or absence of predators. Consequently, many organisms have developed corresponding adaptations, which ensure that specific physiological and behavioral events occur at an appropriate time of the day. In mammals, the underlying mechanism responsible for synchronizing internal biochemical processes with circadian environmental cues has been well studied and is thought to comprise three major components: (1) photoreception by the retina and transmission of neural signals along the retinohypothalamic tract, (2) integration of photoperiodic information with an internal reference circadian pacemaker located in the suprachiasmatic nucleus, and (3) dissemination of circadian information to target organs, via the autonomic nervous system and through humoral pathways. Given the importance that neuroendocrine rhythms play in coordinating normal circadian physiology and behavior, it is plausible that their perturbation during aging contributes to the etiology of age-related pathologies. This mini-review highlights some of the most dramatic rhythmic neuroendocrine changes that occur in primates during aging, focusing primarily on data from the male rhesus macaques (Macaca mulatta). In addition to the age-associated attenuation of hormone levels and reduction of humoral circadian signaling, there are also significant age-related changes in intracrine processing enzymes and hormone receptors which may further affect the functional efficacy of these hormones. Rhesus macaques, like humans, are large diurnal primates and show many of the same physiological and behavioral circadian changes during aging. Consequently, they represent an ideal translational animal model in which to study the causes and consequences of age-associated internal circadian disruption and in which to evaluate novel therapies.     

Temporary Right Ventricular Mechanical Support in High‐Risk Left Ventricular Assist Device Recipients Versus Permanent Biventricular or Total Artificial Heart Support

Early planned institution of temporary right ventricular assist device (RVAD) support with the CentriMag (Levitronix LLC, Waltham, MA, USA) in left ventricular assist device (LVAD) recipients was compared with permanent biventricular assist device (BVAD) or total artificial heart (TAH) support. Between 2007 and 2011, 77 patients (age range: 25–70 years) with preoperative evidence of biventricular dysfunction (University of Pennsylvania score >50; University of Michigan score >5) were included. Forty‐six patients (38 men; median age 54.5 years, range: 25–70 years) underwent LVAD placement combined with temporary RVAD support (group A); in 31 patients (25 men; median age 56.7 years, range: 28–68 years), a permanent BVAD or TAH implantation (group B) was performed. Within 30 days, 12 patients from group A (26.08%) and 14 patients from group B (45.1%) died on mechanical support (P = 0.02). Thirty patients (65.2%) in group A were weaned from temporary RVAD support and three (6.5%) underwent permanent RVAD (HeartWare, Inc., Framingham, MA, USA) placement. A total of 26 patients (56.5%) were discharged home in group A versus 17 (54.8%) in group B (P = 0.56). Three patients (8.5%) received heart transplantation in group A and six (19.3%) in group B (P = 0.04). In group A, 90‐day and 6‐month survival was 54.3% (n = 25) versus 51.6% (n = 16) in group B (P = 0.66). In group A, 1‐year survival was 45.6% (n = 21) versus 45.1% (n = 14) in group B (P = 0.81). The strategy of planned temporary RVAD support in LVAD recipients showed encouraging results if compared with those of a similar permanent BVAD/TAH population. Weaning from and removal of the temporary RVAD support may allow patients to be on LVAD support only despite preoperative biventricular dysfunction.     

Research on the Grinding Energy Density in a Jet Mill

Raw materials are used in many industrial technologies. The raw material frequently has to be prepared as an intermediate with an appropriate particle size distribution, which requires the use of grinding. In grinding processes, energy consumption is a very important profitability criterion for the applied particular size reduction technology. The paper describes the comminution process that takes place in the jet mill using a modified form of the thermodynamic theory of grinding. In this theory, new material characteristics have been added: the surface and volumetric density of grinding energy. The thermodynamic theory is a combination of the classical Kick’s theory and the modified form of Rittinger’s theory. The tested physical magnitudes are a measure of the energy consumption of the grinding process. They describe the energy that must be provided in the grinding process to overcome interactions between particles related to the volume and surface of the material. Knowledge of these magnitudes is necessary to model thermomechanical phenomena in the solid state. The paper presents the results of research on comminution in a jet mill, on the basis of which the values of the tested material magnitudes were determined. It is graphically shown how the values of the tested magnitudes depend on the grain size of the ground samples.     

Impact of moderate calorie restriction on testicular morphology and endocrine function in adult rhesus macaques (Macaca mulatta)

We previously reported that moderate calorie restriction (CR) has minimal impact on testicular gene expression in young adult rhesus macaques, and no obvious negative impact on semen quality or plasma testosterone levels. We now extend these findings by examining the influence of CR on various aspects of the reproductive axis of older males, including 24-h circulating testosterone levels, testicular gene expression, and testicular morphology. Young adult and old adult male rhesus macaques were subjected to either 30 % CR for 5–7 years, or were fed a standard control diet. Analysis of the 24-h plasma testosterone profiles revealed a significant age-associated decline, but no evidence for CR-induced suppression in either the young or old males. Similarly, expression profiling of key genes associated with testosterone biosynthesis and Leydig cell maintenance showed no significant CR-induced changes in either the young or old animals. The only evidence for CR-associated negative effects on the testis was detected in the old animals at the histological level; when old CR animals were compared with their age-matched controls, there was a modest decrease in seminiferous tubule diameter and epithelium height, with a concomitant increase in the number of depleted germ cell lines. Reassuringly, data from this study and our previous study suggest that moderate CR does not negatively impact 24-h plasma testosterone profiles or testicular gene expression. Although there appear to be some minor CR-induced effects on testicular morphology in old animals, it is unclear if these would significantly compromise fertility.     

Determination of Heat Transfer Coefficient for Air-Atomized Water Spray Cooling and Its Application in Modeling of Thermomechanical Controlled Processing of Die Forgings

The paper presents the method and results of determination of heat transfer coefficient for air-atomized water spray cooling with consideration of infrastructural factors of industrial cooling conveyor, such as effect of accelerated air. The established values of heat transfer coefficient were implemented into a numerical model of cooling line, with special definition of sprayers and the movement of the part subjected to quenching. After quantitative validation on selected samples, the obtained coefficients were used for the solution of the technological problem by means of localized cooling rate enhancement, which forms a case study confirming reliability of the established water spray heat transfer functions and suitability of the determined models for design of thermomechanical controlled processing of complex-geometry parts.