Artificial organs
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In patients requiring left ventricular assist device (LVAD) support, it can be difficult to ascertain suitability for long-term mechanical support with LVAD and eventual transplantation. LVAD implantation in a shocked patient is associated with increased morbidity and mortality. Interest is growing in the utilization of extracorporeal life support (ECLS) as a bridge-to-bridge support for these critically unwell patients. ⋯ Preoperative morbidity in the ECLS bridge group was reflected by increased postoperative intensive care duration, blood loss, blood product use, and postoperative renal failure, but without negative impact upon survival when compared with the no ECLS group. ECLS stabilization improved end-organ function pre-VAD implant with significant improvements in hepatic and renal dysfunction. This series demonstrates that the use of ECLS bridge to VAD stabilizes end-organ dysfunction and reduces VAD implant perioperative mortality from that traditionally reported in these "crash and burn" patients.
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Comparative Study
Changes in Spirometry After Left Ventricular Assist Device Implantation.
Left ventricular assist devices (LVADs) are increasingly being used as life-saving therapy in patients with end-stage heart failure. The changes in spirometry following LVAD implantation and subsequent unloading of the left ventricle and pulmonary circulation are unknown. In this study, we explored long-term changes in spirometry after LVAD placement. ⋯ Our results indicated that pulmonary function tests were significantly reduced after LVAD placement (forced expiratory volume in one second [FEV1 ]: 1.9 vs.1.7, P = 0.016; forced vital capacity [FVC]: 2.61 vs. 2.38, P = 0.03; diffusing capacity of the lungs for carbon monoxide [DLCO]: 14.75 vs. 11.01, P = 0.01). Subgroup analysis revealed greater impairment in lung function in patients receiving HeartMate II (Thoratec, Pleasanton, CA, USA) LVADs compared with those receiving HeartWare (HeartWare, Framingham, MA, USA) devices. These unexpected findings may result from restriction of left anterior hemi-diaphragm; however, further prospective studies to validate our findings are warranted.
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Implantable left ventricular assist devices (LVADs) have been adapted clinically for right-sided mechanical circulatory support (RVAD). Previous studies on RVAD support have established the benefits of outflow cannula restriction and rotational speed reduction, and recent literature has focused on assessing either the degree of outflow cannula restriction required to simulate left-sided afterload, or the limitation of RVAD rotational speeds. Anecdotally, the utility of outflow cannula restriction has been questioned, with suggestion that banding may be unnecessary and may be replaced simply by varying the outflow conduit length. ⋯ We assessed the pumps' ability to maintain hemodynamic stability with and without banding; and with varying outflow cannulae length (20, 40, and 60 cm). Increased length of the outflow conduit was found to produce significantly increased afterload to the device, but this was not found to be necessary to maintain the device within the manufacturer's recommended operational parameters under a simulated normal physiological setting of mild and severe right ventricular (RV) failure. We hypothesize that 40 cm of outflow conduit, laid down along the diaphragm and then up over the RV to reach the pulmonary trunk, will generate sufficient resistance to maintain normal pump function.
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The trend in neural prostheses using selective nerve stimulation for electrical stimulation therapies is headed toward single-part systems having a large number of working electrodes (WEs), each of which selectively stimulate neural tissue or record neural response (NR). The present article reviews the electrochemical and electrophysiological performance of platinum WE within a ninety-nine-electrode spiral cuff for selective nerve stimulation and recording of peripheral nerves, with a focus on the vagus nerve (VN). The electrochemical properties of the WE were studied in vitro using the electrochemical impedance spectroscopy (EIS) technique. ⋯ The EIS results revealed capacitive charge transfer predominance, which is a highly desirable property. Electrophysiological performance testing indicated the potential existence of certain parameters and waveforms of the stimulus for which the contribution of the A-fibers to the NR decreased slightly and that of the B-fibers increased slightly. Findings show that the design of the stimulating electrodes, based on the EIS and ECM results, could act as a useful tool for nerve cuff development.