Mechanical circulatory support devices have become an important treatment tool for severe acute and chronic heart failure, since heart transplantation cannot meet the demands because of a lack of available donor organs. Since implantation of the first ventricular assist device a constant development of the suitability of these devices has been made. This review will introduce different generations of left ventricular assist devices (LVAD) and elaborate on clinical indications, risk stratification and current literature.

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e65Objective: Cyclic recruitment and derecruitment of atelectasis can occur during mechanical ventilation, especially in injured lungs. Experimentally, cyclic recruitment and derecruitment can be quantified by respiration-dependent changes in Pao 2 (ΔPao 2 ), reflecting the varying intrapulmonary shunt fraction within the respiratory cycle. This study investigated the effect of inspiration to expiration ratio upon ΔPao 2 and Horowitz index. Design: Prospective randomized study.Setting: Laboratory investigation. Subjects: Piglets, average weight 30 ± 2 kg. Interventions: At respiratory rate 6 breaths/min, end-inspiratory pressure (P endinsp ) 40 cm H 2 O, positive end-expiratory pressure 5 cm H 2 O, and Fio 2 1.0, measurements were performed at randomly set inspiration to expiration ratios during baseline healthy and mild surfactant depletion injury. Lung damage was titrated by repetitive surfactant washout to induce maximal cyclic recruitment and derecruitment as measured by multifrequency phase fluorimetry. Regional ventilation distribution was evaluated by electrical impedance tomography.Step changes in airway pressure from 5 to 40 cm H 2 O and vice versa were performed after lavage to calculate Po 2 -based recruitment and derecruitment time constants (TAU). Measurements and Main Results: In baseline healthy, cyclic recruitment and derecruitment could not be provoked, whereas in model acute respiratory distress syndrome, the highest ΔPao 2 were routinely detected at an inspiration to expiration ratio of 1:4 (range, 52-277 torr [6.9-36.9 kPa]). Shorter expiration time reduced cyclic recruitment and derecruitment significantly (158 ± 85 torr [21.1 ± 11.3 kPa] [inspiration to expiration ratio, 1:4]; 25 ± 12 torr [3.3 ± 1.6 kPa] [inspiration to expiration ratio, 4:1]; p < 0.0001), whereas the Pao 2 /Fio 2 ratio increased (267 ± 50 [inspiration to expiration ratio, 1:4]; 424 ± 53 [inspiration to expiration ratio, 4:1]; p < 0.0001). Correspondingly, regional ventilation redistributed toward dependent lung regions (p < 0.0001). Recruitment was much faster (TAU: fast 1.6 s [78%]; slow 9.2 s) than derecruitment (TAU: fast 3.1 s [87%]; slow 17.7 s) (p = 0.0078). Conclusions: Inverse ratio ventilation minimizes cyclic recruitment and derecruitment of atelectasis in an experimental model of surfactant-depleted pigs. Time constants for recruitment and derecruitment, and regional ventilation distribution, reflect these findings and highlight the time dependency of cyclic recruitment and derecruitment. (Crit Care Med 2015; 43:e65-e74)

OBJECTIVES Our goal was to present histopathological findings of human explants of a tissue-engineered bovine pericardium CardioCel (Admedus Regen Pty Ltd, Malaga, WA, Australia) used for heart valve repair in patients with congenital and acquired heart valve disease. METHODS Sixty patients underwent heart valve repair from May 2014 to November 2018 using CardioCel as a substitute for valve tissue. We identified 9 cases in which the CardioCel patch was explanted following valve repair and available for histomorphological analyses. CardioCel explants were evaluated histologically using haematoxylin and oeosin, Elastica van Gieson and immunohistochemical stains. RESULTS The indications for explantation were related to the CardioCel patch in 6 patients. Median time between the implantation and explantation was 242 (range 3–1247) days. We demonstrated a characteristic remodelling pattern with superficial coating of the tissue-engineered bovine pericardium by granulation tissue composed of histiocytes, few lymphocytes and fibrin. We had 2 cases with a multifocal nodular disruption, fragmentation and sclerosis of the decellularized collagen matrix with focal calcification after 795 and 1247 days in situ. CONCLUSIONS Our data suggest that the tissue-engineered CardioCel patch is initially tolerated in the valvular position in the majority of patients. However, we also experienced graft failures that showed degeneration with fragmentation of the collagen matrix and even 2 cases with focal calcification evident from the histopathological analysis. Further analyses of mid- and long-term performance are mandatory.