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This paper explores new ways to use energy shaping and regulation methods in walking systems to generate new passive-like gaits and dynamically transition between them. We recapitulate a control framework for Lagrangian hybrid systems, and show that regulating a state varying energy function is equivalent to applying energy shaping and regulating the system to a constant energy value. We then consider a simple one-dimensional hopping robot and show how energy shaping and regulation control can be used to generate and transition between nearly globally stable hopping limit cycles. The principles from this example are then applied on two canonical walking models, the spring loaded inverted pendulum (SLIP) and compass gait biped, to generate and transition between locomotive gaits. These examples show that piecewise jumps in control parameters can be used to achieve stable changes in desired gait characteristics dynamically/online.

BACKGROUND The national training surveys was first started in 2006, with an aim to determine the quality of the national training standard. All trainees working in a General Medical Council approved training post are required to complete the survey. We aimed to evaluate cardiothoracic trainees' satisfaction and determine whether there is variation in the United Kingdom. METHOD The national training survey report in cardiothoracic surgery from 2012 to 2019 was obtained from the General Medical Council website. The cardiothoracic centers were divided based on their geographic locations. Comparisons in all 18 indicators in the national training surveys report were made between the four counties (national) and four local education training boards (LETBs) in England (Regional). Centers with less than 4 years of data were excluded from this study. RESULTS Thirty-three cardiothoracic centers are included in this study The top three areas that trainees are most satisfied are clinical supervision (out of hours) (91.65), clinical supervision (90.65), and educational supervision (88.27). On the other hand, trainees are less satisfying with the handover (62.63), rota design (61.91), and workload (45.07). It is worth noting that workload is the only area of less than 60%. In addition, there is no national variation in all 18 indicators CONCLUSION: Our data suggested that there is no difference in overall trainee satisfaction in the United Kingdom. However, there are differences in various indicators between England and the three other nations. Individual hospital should reflect on trainees' evaluation on the national training surveys report and improve on specific areas if deemed unsatisfactory.

This paper details a decentralized passivity-based control (PBC) to improve the robustness of biped locomotion in the presence of gait-generating external torques and parametric errors in the biped model. Previous work demonstrated a passive output for biped systems based on a generalized energy that, when directly used for feedback control, increases the basin of attraction and convergence rate of the biped to a stable limit cycle. This paper extends the concept with a theoretical framework to address both uncertainty in the biped model and a lack of sensing hardware, by allowing the designer to neglect arbitrary states and parameters in the system. This framework also allows the control to be implemented on wearable devices, such as a lower limb exoskeleton or powered prosthesis, without needing a model of the user's dynamics. Simulations on a six-link biped model demonstrate that the proposed control scheme increases the convergence rate of the biped to a walking gait and improves the robustness to perturbations and to changes in ground slope.

This paper offers a novel generalization of a passivity-based, energy tracking controller for robust bipedal walking. Past work has shown that a biped limit cycle with a known, constant mechanical energy can be made robust to uneven terrains and disturbances by actively driving energy to that reference. However, the assumption of a known, constant mechanical energy has limited application of this passivity-based method to simple toy models (often passive walkers). The method presented in this paper allows the passivity-based controller to be used in combination with an arbitrary inner-loop control that creates a limit cycle with a constant generalized system energy. We also show that the proposed control method accommodates arbitrary degrees of underactuation. Simulations on a 7-link biped model demonstrate that the proposed control scheme enlarges the basin of attraction, increases the convergence rate to the limit cycle, and improves robustness to ground slopes.

Background Right ventricular assist devices (RVADs) have been proposed to improve exposure of the coronary arteries in off-pump surgery. In this study we investigated the impact of the A-Med RVAD on inflammatory response and organ function in patients undergoing coronary artery bypass grafting. Methods Sixty patients were prospectively randomized to conventional surgery with cardiopulmonary bypass (CPB) and cardioplegic arrest, beating heart surgery (off-pump), or beating heart surgery with the RVAD. Serial blood samples were collected postoperatively, for analysis of inflammatory markers, troponin I, protein S100, and free hemoglobin. Renal tubular function was assessed by measuring urine N -acetyl-glucosaminidase activity. Results No hospital deaths or major postoperative complications occurred in the study population. Interleukin-6, interleukin-8, C3a, and troponin I levels after surgery were significantly higher in the CPB group compared with the off-pump and RVAD groups. Free hemoglobin levels immediately after the operation, peak and total S100 levels, and N -acetyl-glucosaminidase activity were also significantly higher in the CPB group. Conclusions Off-pump coronary revascularization, with or without RVAD, reduces inflammatory response, myocardial, neurologic, and renal injury, and decreases hemolysis when compared with conventional surgery with CPB and cardioplegic arrest.

Objectives: To determine whether patients with critical left main stem (LMS) coronary artery disease can undergo off-pump coronary artery bypass (OPCAB) surgery safely and successfully. Methods: From May 1996 to March 2000 data for patients with critical ($50%) LMS stenosis who underwent conventional coronary artery bypass surgery with cardiopulmonary bypass (CCAB) or without (OPCAB) were collected prospectively using the Patient Analysis & Tracking System. A reusable pressure stabilizer, intra-coronary shunts and a single posterior pericardial stitch exposure technique were used in all OPCAB cases. Non-randomized, retrospective data analysis included demographic and preoperative risk factors, operative details, clinical outcome and early follow-up. Results: During the study period 387 patients with LMS stenosis underwent surgery (OPCAB na 75, CCAB na 312). Groups were similar in terms of preoperative and intraoperative variables although CCAB patients received significantly more grafts per patient (3.1 ^ 0.73 vs. 2.6 ^ 0.76, P # 0:001). Mortality was similar in both groups (OPCAB 1.3% vs. CCAB 2.6%). OPCAB patients when compared to CCAB patients had a lower requirement for postoperative inotropes (12.0% vs. 38.1%, Pa 0:0001), temporary postoperative pacing (2.7% vs. 10.1%, Pa 0:02), and blood product transfusion (6.7% vs. 31.4%, P , 0:0001), a lower incidence of postoperative chest infection (0% vs. 6.7%, Pa 0:02) and a slightly reduced postoperative length of stay (7.9 ^ 5.46 vs. 8.3 ^ 5.11 days, Pa 0:01). At 24 months follow-up, CCAB and OPCAB actuarial survival was 94.1 ^ 1.7% and 97.7 ^ 2.3%, respectively. Conclusions: OPCAB surgery is safe and effective in patients with critical LMS disease. q 2001 Elsevier Science B.V. All rights reserved.

Despite a significantly lower incidence of wound infection rates and compelling evidence that there is no difference in the degree of preservation of histologic architecture, vascular tone, or vasomotor reactivity of veins harvested with the Mayo dissector (Johnson and Johnson, Langhorne, PA) and a similar graft patency compared with the open method, use of the Mayo dissector still remains limited, probably because of a lack of evidence regarding the functional quality of the vein. In modern practice, although endoscopic vein harvest is gaining popularity, the Mayo dissector (Figure 1) still remains a satisfactory and inexpensive, albeit underused, alternative for vein harvesting, and hence we sought to examine the functional quality of the veins harvested with the Mayo extraluminal dissector. Nitric oxide (NO), a vasoactive molecule produced from the endothelium, is a marker of endothelial function. NO is associated with a diminished incidence of neointimal proliferation, producing these effects through stimulation of soluble guanylate cyclase and generation of cyclic guanosine monophosphate (cGMP). To compare the functional ability of harvested saphenous veins with the Mayo stripper and conventional open dissection, we measured cGMP production ex vivo after stimulation with specific activators of the NO–cGMP axis.

Background . Pulmonary xenotransplantation is not possible because of hyperacute lung injury, the pathogenesis of which is unknown. This study evaluates complement-dependent pathways of pulmonary injury during heterologous perfusion of swine lungs. Methods . Lungs from unmodified swine and swine expressing human decay-accelerating factor and human CD59 (hDAF/hCD59 swine) were perfused with either human plasma or baboon blood. Pulmonary vascular resistance and static pulmonary compliance were measured serially, and swine lung tissue were examined by light microscopy. Complement activation was assessed by serial measurements of baboon plasma C3a-desArg concentrations. Results . Perfusion of unmodified swine lungs with human plasma and baboon blood resulted in hyperacute lung injury within minutes of perfusion. However, function was preserved in swine lungs expressing human decay-accelerating factor and human CD59. In both study groups, xenogeneic perfusion with baboon blood resulted in at least a sevenfold increase in plasma C3a-desArg levels suggesting transient activation of complement. Conclusions . Lungs from swine expressing human decay-accelerating factor and human CD59 were resistant to injury during perfusion with human plasma and baboon blood, indicating that complement mediated some of the features of xenogeneic acute lung injury.

Background. The pathogenesis of acute pulmonary xenograft injury has not yet been determined. The present study evaluates the role of complement in mediating pulmonary xenograft dysfunction by using cobra venom factor (CVF) to deplete recipient complement and transgenic swine, which express human regulators of complement activation (human decay-accelerating factor [hDAF] and hCD59). Methods. Fifteen orthotopic lung transplants were performed as follows: group I, swine-to-swine (n=5); group II, unmodified swine-to-baboon (n=3); group III, unmodified swine-to-(CVF treated) baboon (n=3); and group IV, hCD59/hDAF swine-to-baboon (n=4). Left pulmonary artery flow and pulmonary vascular resistance were measured at 30-min intervals. Serial lung biopsies were examined by light microscopy and immunofluorescence. The activation of complement was quantified by measurement of baboon plasma CH50 and C4 functional activity. Results. Group II xenotransplants ceased functioning within 30 min of reperfusion. Histopathologic abnormalities included erythrocyte/platelet aggregates and hemorrhagic pulmonary edema. Groups I and IV showed excellent function throughout. hDAF/hCD59 lungs (group IV) showed trace venular fibrin plugs and moderate loss of alveolar architecture. Pretreatment with CVF (group III) was ineffective in preventing xenograft injury. Conclusions. These results characterize the fundamental features of discordant pulmonary xenotransplantation. Correction of the known defects in the regulation of heterologous complement activation was partially effective in preventing pulmonary xenograft dysfunction, suggesting that complement mediates, in part, some of the features of acute lung injury after discordant lung xenotransplantation.

The use of nonhuman lung donors, such as swine, has the potential to provide an unlimited supply of organs. However, hyperacute rejection has prevented pulmonary xenotransplantation. Objective: Our aim was to test the hypothesis that immunodepletion by pretransplantation swine lung perfusion will prevent hyperacute swine-to-primate pulmonary xenograft rejection and allow for a functional swine pulmonary xenograft. Methods: Seven baboons underwent left pneumonectomy followed by orthotopic transplantation of the swine left lung. Four baboons received immunodepletion by perfusion with swine lungs before transplantation, and three received no treatment before transplantation. Results: After transplantation, pulmonary xenografts from immunodepleted baboons had a low pulmonary vascular resistance and a high pulmonary blood flow compared with control animals, which had a high pulmonary vascular resistance and a low pulmonary blood flow. After 60 minutes of reperfusion, three of four immunodepleted animals also tolerated complete occlusion of the right pulmonary artery, with the baboon relying completely on the swine pulmonary xenograft for respiratory function for 11 hours. Pathologic analysis of peripheral lung biopsy specimens taken from control lungs displayed alveolar disruption and hemorrhage within small vessels, whereas swine lungs transplanted into immunodepleted baboons displayed little histologic evidence of injury. Furthermore, pulmonary xenografts transplanted into immunodepleted baboons demonstrated excellent respiratory function and adequate hemodynamics during occlusion of the right pulmonary artery. Conclusion: Hyperacute pulmonary xenograft rejection can be prevented by pretransplantation swine lung perfusion. Swine pulmonary xenografts can provide complete respiratory support in primates when rejection is prevented. (J Thorac Cardiovasc Surg 1998:115;19-27)

Pulmonary transplantation is currently limited by the number of suitable cadaver donor lungs. For this reason, pulmonary xenotransplantation is currently being investigated. Objective: Our goal was to assess the role of complement in pulmonary xenograft dysfunction. Methods: The pulmonary function of swine expressing human decay accelerating factor and human CD59 (n = 6) was compared with that of the lungs from nontransgenic (control) swine (n = 6) during perfusion with human plasma. Results: After 2 hours of perfusion, the pulmonary vascular resistance was 1624 ± 408 dynes · sec · cm−5 in control lungs and 908 ± 68 dynes · sec · cm−5 in transgenic lungs (p < 0.05). Control lungs had a venous oxygen tension of 271 ± 23 mm Hg with a ratio of venous oxygen tension to inspired oxygen fraction of 452 ± 38 at 2 hours of perfusion; transgenic lungs had a venous oxygen tension of 398 ± 11 mm Hg and a ratio of venous oxygen tension to inspired oxygen fraction of 663 ± 18 (p < 0.05). Control lungs showed a decrease of 79.8% ± 3.7% in static pulmonary compliance by 2 hours, versus a 12.0% ± 8.1% decrease by the transgenic lungs (p < 0.05). The control lungs also developed 561.7 ± 196.2 ml of airway edema over 2 hours, in contrast to 6.5 ± 1.7 ml in transgenic lungs (p < 0.05). Conclusion: Lungs from swine expressing human decay accelerating factor and human CD59 functioned better than nontransgenic swine lungs when perfused with human plasma. These results suggest that complement activation is involved in producing acute pulmonary xenograft dysfunction and demonstrate that lungs from swine expressing human decay accelerating factor and human CD59 are protected against pulmonary injury when perfused with human plasma. (J Thorac Cardiovasc Surg 1997;113:390-8)

Accessory spleniculi are present in the thoracic cavity without a history of trauma due to anomalies in the development of spleen. We report the case of a 62-year-old woman with hereditary spherocytosis and previous splenectomy with an incidental mass on a chest radiograph and an indeterminate diagnosis on needle biopsy. The probable sequence of embryological events that may explain the anatomic presence of splenic tissue in the thorax is discussed.

Background Postoperative atrial fibrillation is still a common complication in patients undergoing coronary artery bypass grafting. The aim of this study was to evaluate the effect of preoperative statin therapy on new onset of postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting. Methods Of 8,946 patients undergoing isolated coronary artery bypass grafting at the Bristol Heart Institute from April 1996 to September 2006, 6,321 (70.6%) received preoperative statins. Of these, 2,152 patients (statin group) were matched to a control group (no statin) by propensity score analysis. Results Preoperative characteristics, number of distal anastomoses, and the use of off -pump procedures were similar in both groups. Hospital mortality was 1.3% (56 patients) with no difference between the two groups. Postoperative atrial fibrillation was significantly higher in the statin compared with the no statin group (411, 19.5%, versus 336; 15.8% respectively; p = 0.002). In a multivariate regression analysis, age (odds ratio [OR], 1.04; 95% confidence interval [CI], 1.02 to 1.05), pulmonary disease (OR, 1.42; 95% CI, 1.12–1.82), history of paroxysmal atrial fibrillation (OR, 3; 95% CI, 2.13 to 4.19), preoperative angiotensin-converting enzyme inhibitor therapy (OR, 1.26; 95% CI, 1.07 to 1.49), ejection fraction less than 0.30 (OR, 1.71; 95% CI, 1.22 to 2.38), emergency operations (OR, 4.5; 95% CI, 2 to 10.12), and preoperative statin treatment (OR, 1.31; 95% CI, 1.11 to 1.55) were all independent predictors of postoperative atrial fibrillation. Conclusions Preoperative statin is associated with a significantly higher incidence of postoperative atrial fibrillation compared with no statin treatment in patients undergoing isolated coronary artery bypass grafting.

Background . This study investigated the hemodynamic changes in patients undergoing multiple vessel beating heart coronary revascularization in the presence or absence of an intracoronary shunt. Methods . Forty patients were randomized to off-pump with a shunt (n = 20) or with the proximal coronary artery occluded by a soft snare (n = 20). Hemodynamic measurements were recorded at base line, during construction, and after completion of each distal anastomosis. Results . Grafting of the left anterior descending coronary artery anastomosis was associated with a significant decrease in stroke volume, cardiac index, and mean arterial pressure, and an increase in pulmonary capillary wedge pressure and systemic vascular resistance in the snare but not in the shunt group. During grafting of the posterior descending coronary artery there was a marked decrease in stroke volume and cardiac index, and an increase in central venous pressure in both groups, and an increase in heart rate, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, and systemic vascular resistance only in the snare group. The most extensive changes were observed during the circumflex coronary artery anastomosis with a reduction in stroke volume, cardiac index, and mean arterial pressure, and an increase in central venous pressure, pulmonary capillary wedge pressure, pulmonary arterial pressure, and systemic vascular resistance in both groups. In all settings, these changes were transient and recovered after the heart was returned to its anatomical position in the shunt group, whereas stroke volume and cardiac index remained reduced, and systemic vascular resistance was elevated in all settings in the snare group. Conclusions . Stabilization of the left anterior descending coronary artery to perform the anastomosis resulted in temporary hemodynamic changes, which are prevented by the use of an intracoronary shunt. The hemodynamic deterioration during the construction of the posterior descending coronary artery and circumflex coronary artery anastomoses is transient in the shunt group, whereas the snaring technique is associated with an impairment of early functional recovery.

Background . Although there is growing evidence to suggest that the administration of magnesium (Mg 2+ ) to patients undergoing coronary artery bypass grafting (CABG) and to patients after myocardial infarction is beneficial, the addition of Mg 2+ to cardioplegic solutions remains controversial. The aim of this study was to compare the effects of intermittent warm blood cardioplegia with and without Mg 2+ supplementation on the early postoperative clinical outcomes in patients undergoing both elective or urgent CABG. Methods . Four hundred patients undergoing CABG were prospectively randomized to receive either blood cardioplegia without Mg 2+ (BC, n=200) or supplemented with Mg 2+ (BC-Mg 2+ , n=200). Serial plasma Mg 2+ concentrations were recorded at base line and postoperatively from days 1 to 4. Results . Patient characteristics were similar and no significant differences were found in early mortality and morbidity in the two groups. Analysis of 178 patients undergoing urgent CABG for unstable symptoms (BC = 95, BC-Mg 2+ = 83) demonstrated a significantly lower requirement for internal defibrillation and temporary epicardial pacing in the BC-Mg 2+ group. Furthermore, there was a nearly twofold lower incidence of new postoperative atrial fibrillation in the BC-Mg 2+ group compared with the BC group (19% versus 34%, p = 0.03). Postoperative plasma Mg 2+ levels were consistently lower in those patients who developed new postoperative atrial fibrillation compared with those who did not ( p = 0.05). Conclusions . The addition of Mg 2+ to warm blood cardioplegia resulted in a lower incidence of intraoperative and postoperative arrhythmias in patients undergoing urgent CABG for unstable angina.

John Anthony Morgan (“Tony”) grew up around Cardigan Bay in South Wales before becoming a scholar at Epsom College in Surrey. His love of organ recital music took him to Cambridge University, where he was Duckworth Exhibitioner of Jesus College. He also found time to study medicine and did his clinical undergraduate training at Guy’s in London. After his graduation in 1971, he trained in general and cardiothoracic surgery in London but moved to Groote Schuur Hospital in Cape Town in 1976. It …

Objective: Pulmonary transplantation has become the preferred treatment for end-stage lung disease, but application of the procedure is limited because of a paucity of donors. One way to solve donor limitations is to use animal organs as a donor source or xenotransplantation. The current barrier to pulmonary xenotransplantation is the rapid failure of the pulmonary xenograft. Although antibodies are known to play a role in heart and kidney xenograft rejection, their involvement in lung dysfunction is less defined. This project was designed to define the role of antibodies in pulmonary graft rejection in a pig-to-baboon model. Methods: Orthotopic transgenic swine left lung transplants were performed in baboons depleted of antibodies by one of three techniques before transplantation: (1) ex vivo swine kidney perfusion, (2) total immunoglobulin-depleting column perfusion, and (3) ex vivo swine lung perfusion. Results were compared with those of transgenic swine lung transplants in unmodified baboons. Results: All three techniques of antibody removal resulted in depletion of xenoreactive antibodies. Only pretransplantation lung perfusion improved pulmonary xenograft function compared with lung transplantation in unmodified baboons. Conclusions: The pathogenesis of pulmonary injury in a swine-to-primate transplant model is different from that in renal and cardiac xenografts. Depletion of antibodies alone does not have a beneficial effect and may actually be detrimental. (J Thorac Cardiovasc Surg 2000;120:29-38)