vendex and Heart-Failure

A novel pump, the left atrial assist device (LAAD), is a device specifically for the treatment of heart failure with preserved ejection fraction (HFpEF). The LAAD is a mixed-flow pump that is implanted in the mitral position and delivers blood from the left atrium to the left ventricle. During the development process, we aimed to explore whether device activation in torque control (TC) mode would improve the function of the LAAD. The TC mode causes adjustment of the pump speed automatically during each cardiac cycle in order to maintain a specified torque. In this study, we tested four different TC settings (TC modes 0.9, 1.0, 1.25, and 1.5) using an in vitro mock circulatory loop. Mild, moderate, and severe diastolic heart failure (DHF) conditions, as well as normal heart condition, were simulated with the four TC modes. Also, we evaluated the LAAD in vivo with three calves. The LAAD was implanted at the mitral position with four TC settings (TC modes 0.9, 1.0, 1.1, 1.2). With LAAD support, the in vitro cardiac output and aortic pressure recovered to normal heart levels at TC 1.25 and 1.5 even under severe DHF conditions with little pump regurgitation. The TC mode tested in vivo with three calves, and it also showed favorable result without elevating the left ventricular end-diastolic pressure. These initial in vitro and in vivo results suggest that the TC mode could be potentially effective, and the LAAD could be a treatment option for HFpEF patients.

Topics: Animals; Atrial Fibrillation; Cattle; Heart Atria; Heart Failure; Heart Failure, Diastolic; Heart-Assist Devices; Humans; Stroke Volume; Torque; Ventricular Function, Left

Left ventricular (LV) twist may be a compensatory mechanism to preserve ejection fraction (EF). In patients with hypertension, twist varies depending on the left ventricle's degree of remodeling and systolic function; it is increased in those with hypertension with normal EF (HTNEF) and diminished in those with hypertension with low EF (HTLEF). The ratio of collagen-degradation biomarkers in patients with hypertension is higher in those with low EFs than those with preserved EFs and may contribute to remodeling and systolic dysfunction.. The aim of this study was to evaluate the relationship between these biomarkers and LV twist in 82 patients with hypertension, 41 with EFs < 50% (HTLEF group) and 41 with EFs ≥ 50% (HTNEF group). Net LV twist was measured using speckle-tracking echocardiography. Markers of collagen turnover, including serum concentrations of matrix metalloproteinase-1 (MMP1), tissue inhibitor of MMP1 (TIMP1), and the ratio of MMP1 to TIMP1, were measured.. Log TIMP1, log MMP1, and log MMP1/TIMP1 ratio levels were higher in the HTLEF group than the HTNEF group (12.3 ± 0.3 vs 11.8 ± 0.1 [P < .0001], 9.1 ± 0.3 vs 8.0 ± 0.2 [P < .0001], and -3.3 ± 0.3 vs -3.8 ± 0.2 [P < .0001], respectively). Net LV twist was lower in the HTLEF group than the HTNEF group (3.3 ± 1.1 vs 11.7 ± 0.7, P < .0001). An inverse correlation existed between log MMP1/TIMP1 and net LV twist after adjusting for age, EF, duration of heart failure, systolic blood pressure, LV mass index, and LV sphericity index at end-diastole (r = -0.43, P < .0001).. This inverse correlation between twist and loss of myocardial collagen scaffolding in patients with hypertension with heart failure suggests that the integrity of the extracellular matrix may play an important role in preserving myocardial deformation.

Topics: Collagen; Echocardiography; Female; Heart Failure; Humans; Hypertension; Male; Matrix Metalloproteinase 1; Middle Aged; Reproducibility of Results; Sensitivity and Specificity; Tissue Inhibitor of Metalloproteinase-1; Torque; Ventricular Dysfunction, Left

Despite the availability of first-generation extracorporeal mechanical circulatory support (MCS) systems that are widely used throughout the world, there is a need for the next generation of smaller, more portable devices (designed without cables and a minimal number of connectors) that can be used in all in-hospital and transport settings to support patients in heart failure. Moreover, a system that can be universally used for all indications for use including cardiopulmonary bypass (CPB), uni- or biventricular support (VAD), extracorporeal membrane oxygenation (ECMO) and respiratory assist that is suitable for use for adult, neonate, and pediatric patients is desirable. Providing a single, well designed, universal technology could reduce the incidence of human errors by limiting the need for training of hospital staff on a single system for a variety of indications throughout the hospital rather than having to train on multiple complex systems. The objective of this manuscript is to describe preliminary research to develop the first prototype pump for use as a ventricular assist device for pediatric patients with the Inspired Universal MCS technology. The Inspired VAD Universal System is an innovative extracorporeal blood pumping system utilizing novel MagLev technology in a single portable integrated motor/controller unit which can power a variety of different disposable pump modules intended for neonate, pediatric, and adult ventricular and respiratory assistance.. A prototype of the Inspired Pediatric VAD was constructed to determine the hemodynamic requirements for pediatric applications. The magnitude/range of hydraulic torque of the internal impeller was quantified. The hydrodynamic performance of the prototype pump was benchmarked using a static mock flow loop model containing a heated blood analogue solution to test the pump over a range of rotational speeds (500-6000 RPM), flow rates (0-3.5 L/min), and pressures (0 to ~ 420 mmHg). The device was initially powered by a shaft-driven DC motor in lieu of a full MagLev design, which was also used to calculate the fluid torque acting on the impeller.. The pediatric VAD produced flows as high as 4.27 L/min against a pressure of 127 mmHg at 6000 RPM and the generated pressure and flow values fell within the desired design specifications.. The empirically determined performance and torque values establish the requirements for the magnetically levitated motor design to be used in the Inspired Universal MagLev System. This next step in our research and development is to fabricate a fully integrated and functional magnetically levitated pump, motor and controller system that meets the product requirement specifications and achieves a state of readiness for acute ovine animal studies to verify safety and performance of the system.

Topics: Animals; Child; Equipment Design; Heart Failure; Heart-Assist Devices; Hemodynamics; Humans; Sheep; Torque

Left ventricular assist devices (LVADs) have increasingly been used clinically to treat heart failure patients. However, hemolysis, pump thrombosis, infection and bleeding still persist as major limitations of LVAD technology. Assessing LVAD hemocompatibility using a blood shear stress device (BSSD) has clear advantages, as the BSSD could provide a better experimental platform to develop reliable, quantifiable blood trauma assays to perform iterative testing of LVAD designs. In this study, a BSSD was proposed with short blood exposure time and no seals or contact bearings to reduce blood trauma caused by the test platform. Enlarged air-gap drive motor in BSSD is essential to avoid high shear stress; however, it would significantly reduce the motor torque, which may result in inadequate force to drive the entire system. In order to evaluate and optimize the drive motor air-gap to ensure adequate motor torque as well as acceptable range for blood exposure time and shear stress, a numerical brushless DC (BLDC) motor model was established using finite element method (FEM) in numerical simulation software COMSOL. The model was first validated by the experimental results. Then numerical model with different air-gap was evaluated on the torque and speed constant changes. In the end, two equations were generated based on the curves derived from the torque and speed constant calculations. Determining these relationships between motor performance and motor air-gap will facilitate the development of an appropriate BLDC motor size for the BSSD, considering the design limitations in our future work.

Topics: Animals; Heart Failure; Heart-Assist Devices; Hemolysis; Humans; Stress, Mechanical; Torque

Heart failure (HF)-related exercise intolerance is thought to be perpetuated by peripheral skeletal muscle functional, structural, and metabolic abnormalities. We analyzed specific dynamics of muscle contraction in patients with HF compared with healthy, sedentary controls.. Isometric and isokinetic muscle parameters were measured in the dominant upper and lower limbs of 45 HF patients and 15 healthy age-matched controls. Measurements included peak torque normalized to body weight, work normalized to body weight, power, time to peak torque, and acceleration and deceleration to maximum strength times. Body morphometry (dual energy X-ray absorptiometry scan) and circulating fatty acids and ceramides (lipodomics) were analyzed in a subset of subjects (18 HF and 9 controls).. Extension and flexion time-to-peak torque was longer in the lower limbs of HF patients. Furthermore, acceleration and deceleration times in the lower limbs were also prolonged in HF subjects. HF subjects had increased adiposity and decreased lean muscle mass compared with controls. Decreased circulating unsaturated fatty acids and increased ceramides were found in subjects with HF.. Delayed torque development suggests skeletal muscle impairments that may reflect abnormal neuromuscular functional coupling. These impairments may be further compounded by increased adiposity and inflammation associated with increased ceramides.

Topics: Adiposity; Adult; Biomechanical Phenomena; Ceramides; Fatty Acids, Unsaturated; Heart Failure; Humans; Lower Extremity; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Torque

To compare the acute effects of functional electrical stimulation (FES) with 15 and 50 Hertz (Hz) frequencies on muscle strength in patients with heart failure with healthy individuals.. Twenty-two 61.6 ± 1.0 y-old male volunteers were studied: 10 patients with heart failure (functional class II-III) and 12 healthy controls. The isometric muscle peak torque (IMPT) of the quadriceps femoral muscle was measured through a Biodex dynamometer in maximum voluntary contraction (MVC), and under FES of 50 Hz and 15 Hz, which was applied with a 0.4 ms pulse width, 10-s contraction time, 50-s resting time and maximum tolerable intensity.. The IMPT differed in MVC, 50 Hz and 15 Hz FES both in patients (201.9 ± 14, 55.6 ± 13 and 42.1 ± 12 Newton-metre, respectively; p < 0.001) and in controls (179.3 ± 9, 62.4 ± 8 and 52.3 ± 7 Newton-metre, respectively; p < 0.001). There were no differences between the groups. In patients and controls, respectively, the 50 Hz FES corresponded to 27% versus 35% and the 15 Hz to 21% versus 29% of the IMPT generated at the MVC (p < 0.001).. This result can be attributed to the fact that muscle strength is proportional to the stimulation frequency and to the number of recruited motor units. Thus, the higher the frequency, the greater the motor recruiting, producing increased muscle strength.. The IMPT generated by acute 50 Hz application of FES is higher than the one generated by 15 Hz, but it is lower than MVC in controls and patients with heart failure.

Topics: Analysis of Variance; Case-Control Studies; Electric Stimulation Therapy; Heart Failure; Humans; Male; Middle Aged; Muscle Strength; Quadriceps Muscle; Statistics, Nonparametric; Torque; Treatment Outcome

Patients with chronic heart failure (HF) frequently lose muscle mass and function during the course of the disease. A reduction in anabolic stimuli to the muscle has been put forth as a potential mechanism underlying these alterations. The present study examined the hypothesis that skeletal muscle tissue from HF patients would show reduced IGF-1 expression and phosphorylation of signaling molecules downstream of receptor activation. To isolate the unique effect of HF on these variables, we limited the confounding effects of muscle disuse and/or acute disease exacerbation by recruiting controls (n = 11) with similar physical activity levels as HF patients (n = 11) and by testing patients at least 6 mo following any bouts of disease exacerbation/hospitalization. IGF-1 expression in skeletal muscle was similar between patients and controls. Despite this, HF patients were characterized by reduced levels of phospho-Akt/Akt (S473; -43%; P < 0.05), whereas no differences were found in total Akt protein content or phospho- or total protein content of mammalian target of rapamycin (mTOR; S2448), glycogen synthase kinase-3β (GSK-3β; S9), eukaryotic translation initiation factor 4E binding protein-1 (eIF4E-BP; T37/46), p70 ribosomal S6 kinase (p70 S6K; T389), or eIF2Bε (S540). Reduced phospho-Akt/Akt levels and phospho-mTOR/mTOR were related to decreased skeletal muscle myosin protein content (r = 0.602; P < 0.02) and knee extensor isometric torque (r = 0.550; P < 0.05), respectively. Because patients and controls were similar for age, muscle mass, and physical activity, we ascribe the observed alterations in Akt phosphorylation and its relationship to myosin protein content to the unique effects of the HF syndrome.

Topics: Adaptor Proteins, Signal Transducing; Blotting, Western; Body Composition; Cell Cycle Proteins; Female; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Heart Failure; Humans; Insulin-Like Growth Factor I; Male; Muscle, Skeletal; Phosphoproteins; Phosphorylation; Proto-Oncogene Proteins c-akt; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; TOR Serine-Threonine Kinases; Torque

The goal of this study was to determine if heart failure alters knee extensor muscle torque, power production or contractile velocity.. Heart failure patients (n=11; 70.4±4.3 yrs) and controls (n=11; 70.3±3.4 yrs) matched for age and sex were evaluated for knee extensor contractile performance under isometric and isokinetic conditions and body composition by dual energy X-ray absorptiometry. Additionally, we recruited sedentary to minimally active elderly controls to match heart failure patients for habitual physical activity and assessed activity levels using accelerometry.. Groups did not differ for total or regional body composition or average daily physical activity level. Despite similar muscle size and use, heart failure patients exhibited 21-29% lower (P<0.05 to P<0.01) isometric knee extensor torque throughout a range of knee angles, 15-33% lower (P=0.05 to P<0.01) peak concentric torque measured at various isokinetic speeds and corresponding reductions (P=0.05 to P<0.01) in peak power output. Expression of peak isokinetic torque data relative to isometric torque eliminated group differences, suggesting that impaired contractile function under dynamic conditions is explained by deficits in the force generating capacity of muscle. No group differences were found in the time required to reach target velocity during isokinetic contractions, an index of contractile velocity.. Because group differences in muscle torque were independent of age, sex, physical activity level and muscle size, our results suggest that muscle contractile dysfunction in these patients is likely attributable to the heart failure syndrome.

Topics: Aged; Cachexia; Disability Evaluation; Female; Heart Failure; Humans; Isometric Contraction; Knee Joint; Male; Motor Activity; Muscle, Skeletal; Muscular Diseases; Oxygen Consumption; Sedentary Behavior; Torque

Reduction in exercise capacity in patients with chronic heart failure (CHF) has been partially attributed to decreased muscle strength. Training studies reported important variations in strength increases during rehabilitation, ranging between 5% and 70% and depending on the measurement technique: isokinetic dynamometry or the one-repetition maximum (1RM) methods. Therefore, the question arises if both techniques assess the changes in muscle strength in a comparable way.. Thirty patients with CHF, New York Heart Association class II-III, with mean baseline VO2peak of 14.8 +/-3.0 mL x kg(-1) x min(-1) and mean baseline left ventricular ejection fraction of 23.5% T 5.5%, were assessed for knee extensor and knee flexor strength before and after 40 training sessions by isokinetic dynamometry and 1RM method. These two strength measurement techniques were compared using the Bland and Altman method for agreement.. Knee extensor muscle strength increased by 7.4% and knee flexor strength increased by 18.7% if measured by isokinetic testing. With the 1RM method, knee extensor and flexor strength increased by 36% and 100%, respectively. Both techniques were not in agreement for muscle strength assessment; improvements were more important with the 1RM method. Furthermore, statistical analysis showed that the 1RM technique was overestimating strength increases in comparison with isokinetic evaluation, especially for higher strength levels.. In the follow-up of exercise training programs in patients with CHF, isokinetic measurements should be preferentially used to limit bias between measurements at different times.

Topics: Aged; Chronic Disease; Exercise Test; Exercise Tolerance; Heart Failure; Humans; Middle Aged; Muscle Strength; Oxygen Consumption; Physical Fitness; Torque

Electrical myostimulation (EMS) has recently been proposed as an interesting rehabilitation tool in patients with chronic heart failure (CHF). Although its beneficial effects on exercise capacity and muscle strength have been demonstrated, the neuromuscular adaptations responsible for improved performance are not well understood. This preliminary case report was therefore planned to investigate the neural and muscular adaptations to a 5-wk EMS program in one patient. An increase in maximal strength (10.5%) was accompanied by increased twitch torque (13.9%) and slowing of muscle contractile properties (half-relaxation time, time to peak torque, and maximal rate of relaxation increased by 7.1, 31.1, and 16.6%, respectively) without changes in muscle activation. This preliminary case report therefore shows that in a highly deconditioned patient, EMS training improved strength through muscular adaptations rather than by neural changes, suggesting that EMS may be valuable for counterbalancing loss of muscle strength and function common in CHF patients.

Topics: Adaptation, Physiological; Cardiomyopathies; Electric Stimulation; Electromyography; Feasibility Studies; Heart; Heart Failure; Humans; Leg; Male; Middle Aged; Muscle, Skeletal; Myocardial Contraction; Stroke Volume; Torque

Patients with congestive heart failure (CHF) exhibit an impaired exercised tolerance that dramatically limits their functional capacity and alters their quality of life.. The aim of this study was to compare the effects of two types of training programmes on isokinetic muscle strength and aerobic capacities in patients with CHF.. A group of 23 stable CHF patients included consecutively followed an exercise training programme, 3 days a week for 8 weeks. The first group (P1, n=11) exercised on a cycloergometer for 45 min at 65% of peak VO2. The second group (P2, n=12) followed a 45-min combined bicycle and quadricipital strength training. Strength training consisted of 10 series of 10 repetitions at 70% of maximal voluntary force. Incremental maximal cardiopulmonary exercise tests as well as an isokinetic quadricipital dynamometry evaluation were performed before and after training.. In P1, peak VO2 increased by 20% (22.3+/-4.9 versus 17.8+/-4.5 ml min(-1) kg(-1); P<0.05) without any significant change in isokinetic muscle strength. In P2, peak VO2 improved within the same range (20.5+/-2.8 versus 18.6+/-3.7 ml min(-1) kg(-1); P<0.01). This last rehabilitation programme significantly increased isokinetic muscle strength at each angular velocities (+10.5+/-13.5%, P<0.04; +5.6+/-7.0%, P<0.03; for 180 degrees s(-1) and 60 degrees s(-1) respectively). Only the combined endurance/strength training programme was associated with an improvement in both peak VO2 and peripheral muscle strength, two significant parameters of outcome and quality of life in CHF.

Topics: Adult; Aged; Analysis of Variance; Chronic Disease; Exercise Test; Exercise Therapy; Exercise Tolerance; Female; Heart Failure; Humans; Male; Middle Aged; Muscle Strength; Oxygen Consumption; Quality of Life; Statistics, Nonparametric; Torque; Treatment Outcome

Measurement of skeletal muscle strength gains increasing importance as outcome parameter in patients with chronic heart failure. This study aimed at establishing short-term reliability of isokinetic strength measurements of knee extensor and flexor muscles in 38 patients with chronic heart failure. Strength tests were performed on the Cybex 6000 dynamometer. Trunk fixation was restricted to pelvic fixation. Two bouts of strength testing were performed on day 1 and one on day 5. Each isokinetic bout consisted of 3 reciprocal knee extension and flexion movements with an angular speed of 60 degrees per second. Isometric strength was measured at 30 degree knee angulation. Intraclass correlations ranged between 0.96 and 0.99 for isokinetic and isometric peak torque of knee extensor muscles and 0.82-0.96 for flexor muscles. Analysis of repeated measurements showed significant differences among the values of flexor peak torque in the isokinetic mode and between all measurements in the isometric mode (p < 0.05). Pearson's correlation coefficients for isokinetic and isometric extensor peak torques ranged between 0.95 and 0.99, for flexor peak torques between 0.81 and 0.85 (all p < 0.0001). Measurement of isokinetic knee extensor and flexor peak torque is a reliable method to assess muscle strength in patients with chronic heart failure even with altered trunk fixation.

Topics: Adult; Aged; Exercise Therapy; Female; Heart Failure; Humans; Knee Joint; Leg; Male; Middle Aged; Muscle, Skeletal; Reproducibility of Results; Torque; Treatment Outcome; Weight Lifting; Weight-Bearing

Patients with severe chronic heart failure (CHF) suffer from marked weakness of skeletal muscles. Neuromuscular electrical stimulation (NMES) proved to be an alternative to active strength training. The objective of this study was to test the feasibility and effectiveness of NMES in patients with chronic heart failure. Seven patients (56.0 +/- 5.0 years, CHF for 20 +/- 4 months, left ventricular ejection fraction 20.1 +/- 10.0%) finished an 8 week course of NMES of the knee extensor muscles. The stimulator delivered biphasic, symmetric, constant voltage impulses of 0.7 ms pulse width with a frequency of 50 Hz, 2 s on and 6 s off. No adverse effects occurred. After the stimulation period, the isokinetic peak torque of the knee extensor muscles increased by 13% from 101.0 +/- 8.7 Nm to 113.5 +/- 7.2 Nm (p = 0.004). The maximal isometric strength increased by 20% from 294.3 +/- 19.6 N to 354.14 +/- 15.7 N (p = 0.04). This increased muscle strength could be maintained in a 20 min fatigue test indicating decreased muscle fatigue. These results demonstrate that NMES of skeletal muscles in patients with severe chronic heart failure is a promising method for strength training in this group of patients.

Topics: Chronic Disease; Electric Stimulation Therapy; Evaluation Studies as Topic; Feasibility Studies; Female; Heart Failure; Humans; Isometric Contraction; Knee Joint; Male; Middle Aged; Muscle Contraction; Muscle Fatigue; Muscle Weakness; Neuromuscular Junction; Range of Motion, Articular; Stroke Volume; Torque; Ventricular Dysfunction, Left

The exercise intolerance and excessive ventilatory response to exercise of chronic heart failure is associated with abnormalities of skeletal muscle function, in particular a reduction in muscle strength. Isometric and isokinetic leg muscle strength were measured in 10 patients with chronic heart failure and 10 age-matched controls. Each subject undertook maximal exercise testing to measure peak oxygen consumption (V(O2)) and the ventilatory response to exercise as measured by the slope of the relation between ventilation and carbon dioxide production (V(E)/V(CO2) slope). Quadriceps strength (mean (S.D.)) was reduced in heart failure as measured by isometric (444.9 (129.6) N vs. 556.0 (136.0); P<0.01) and isokinetic (123.6 (30.2) Nm vs. 146.8 (40.0); P=0.04). Hamstring strength was also reduced as measured by isokinetic testing (53.6 (15.6) Nm vs. 71.1 (28.1); P=0.02). Isokinetic and isometric strengths correlated, but not closely (r=0.52, P<0.001). There were negative correlations between the V(E)/V(CO2) slope, and isokinetic measures: with average torque, r=-0.62, P<0.004; with peak torque, r=-0.64, P=0.002. We have found evidence for reduced muscle function affecting both knee flexors and extensors. This reduction in muscle strength correlates with the ventilatory response to exercise. These observations lend support to the muscle hypothesis of the generation of symptoms in chronic heart failure.

Topics: Angiotensin-Converting Enzyme Inhibitors; Carbon Dioxide; Case-Control Studies; Diuretics; Exercise Tolerance; Heart Failure; Humans; Isometric Contraction; Knee Joint; Leg; Middle Aged; Muscle Contraction; Muscle, Skeletal; Oxygen Consumption; Physical Exertion; Pulmonary Gas Exchange; Respiration; Tendons; Torque