Methods for improved flexural mechanical properties of 3D-plotted PCL-based scaffolds for heart valve tissue engineering

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Low flow extracorporeal CO2 removal in ARDS patients : a prospective short-term crossover pilot study

Background: Lung protective mechanical ventilation (MV) is the corner stone of therapy for ARDS. However, its use may be limited by respiratory acidosis. This study explored feasibility of, effectiveness and safety of low flow extracorporeal CO2 removal (ECCO2R). Methods: This was a prospective pilot study, using the Abylcap (R) (Bellco) ECCO2R, with crossover off-on-off design (2-h blocks) under stable MV settings, and follow up till end of ECCO2R. Primary endpoint for effectiveness was a 20% reduction of PaCO2 after the first 2-h. Adverse events (AE) were recorded prospectively. We included 10 ARDS patients on MV, with PaO2/FiO(2) = 5 cmH(2)O, FiO(2) titrated to SaO(2) 88-95%, plateau pressure >= 28 cmH(2)O, and respiratory acidosis (pH < 7.25). Results: After 2-h of ECCO2R, 6 patients had a >= 20% decrease in PaCO2 (60%); PaCO2 decreased 28.4% (from 58.4 to 48. 7 mmHg, p = 0.005), and pH increased (1.59%, p = 0.005). ECCO2R was hemodynamically well tolerated. During the whole period of ECCO2R, 6 patients had an AE (60%); bleeding occurred in 5 patients (50%) and circuit thrombosis in 3 patients (30%), these were judged not to be life threatening. Conclusions: In ARDS patients, low flow ECCO2R significantly reduced PaCO2 after 2 h, Follow up during the entire ECCO2R period revealed a high incidence of bleeding and circuit thrombosis

Sutureless replacement of aortic valves with St Jude Medical mechanical valve prostheses and Nitinol attachment rings: feasibility in long-term (90-day) pig experiments

Objective: Nitinol attachment rings (devices) used to attach mechanical aortic valve prostheses suturelessly were studied in long-term (90 days) pig experiments. Methods: The aortic valve was removed and replaced by a device around a St Jude Medical mechanical valve prosthesis in 10 surviving pigs. Supravalvular angiography was done at the end of the operation. No coumarin derivates were given. Results: No or minimal aortic regurgitation was confirmed in all surviving pigs at the end of the operation. Total follow-up was 846 days. In 4 pigs, follow-up was shorter than 90 days (28-75 days); the other 6 pigs did reach 90 days' survival or more. Repeat angiography in 4 pigs at the end of follow-up confirmed the unchanged position of the device at the aortic annulus, without aortic regurgitation. At autopsy, in all pigs the devices proved to be well grown in at the annulus, covered with endothelium, and sometimes tissue overgrowth related to not using coumarin derivates. There was no case of para-device leakage, migration, or embolization. No damage to surrounding anatomic structures or prosthetic valves was found. Conclusions: Nitinol attachment rings can be used to replace the aortic valve suturelessly with St Jude Medical mechanical aortic valve prostheses, without para-device leakage, migration, or damage to the surrounding tissues, in long-term pig experiments during a follow-up of 90 days or more. Refraining from anticoagulation in pigs with mechanical valve prostheses can lead to tissue overgrowth of the valve prosthesis. Further studies are needed to determine long-term feasibility of this method in human beings

Use of a right ventricular continuous flow pump to validate the distensible model of the pulmonary vasculature

In the pulmonary circulation, resistive and compliant properties overlap in the same vessels. Resistance varies nonlinearly with pressure and flow; this relationship is driven by the elastic properties of the vessels. Linehan et al. (1982) correlated the mean pulmonary arterial pressure and mean flow with resistance using an original equation incorporating the distensibility of the pulmonary arteries. The goal of this study was to validate this equation in an in vivo porcine model. In vivo measurements were acquired in 6 pigs. The distensibility coefficient (DC) was measured by placing piezo-electric crystals around the pulmonary artery (PA). In addition to experiments under pulsatile conditions, a right ventricular (RV) bypass system was used to induce a continuous pulmonary flow state. The Linehan's equation was then used to predict the pressure from the flow under continuous flow conditions. The diameter-derived DC was 2.4 %/mmHg (+/- 0.4 %), whereas the surface area-based DC was 4.1 %/mmHg (+/- 0.1 %). An increase in continuous flow was associated with a constant decrease in resistance, which correlated with the diameter-based DC (r=-0.8407, p=0.044) and the surface area-based DC (r=-0.8986, p=0.028). In contrast to the Linehan's equation, our results showed constant or even decreasing pressure as flow increased. Using a model of continuous pulmonary flow induced by an RV assist system, pulmonary pressure could not be predicted based on the flow using the Linehan's equation. Measurements of distensibility based on the diameter of the PA were inversely correlated with the resistance

Effect of aortic stiffness versus stenosis on ventriculo-arterial interaction in an experimental model of coarctation repair

Objectives: The aim of this study was to investigate the effect of short- versus long-segment aortic stiffness and stenosis on ventriculo-arterial interaction in a porcine model of coarctation repair. Methods: Short-long aortic stiffness was created by transection/suture [coarctation (CoA) suture, n = 6] and stenting (stent, n = 5) of the proximal descending aorta. Short-long aortic stenosis was achieved by wrapping a prosthetic graft around the aorta to 1/3-circumference reduction, over a segment length of 1 cm (CoA suture stenosis, n = 5) and 4.5 cm (stent stenosis, n = 6). After 3 months, aortic pressure-flow haemodynamics, aortic distensibility by intravascular ultrasound and left ventricular performance by pressure-volume loops were compared to a Sham group (n = 5) at baseline and during dobutamine administration. Results: The aortic impedance increased with 30.3 (12.6%) and 41.3 (20.9%) (P < 0.001) in CoA stenosis and stent stenosis during inotropic response. Impaired haemodynamic aortic compliance was associated with lower aortic distensibility by intravascular ultrasound, specifically in long-segment stenosis. The ventriculo-arterial coupling was disturbed in both groups with stenosis, with blunted contractile response [Sham 140.3 (19.8%), CoA suture 101.3 (14.5%), CoA suture stenosis 75.0 (8.4%), stent 115.5 (12.7%), stent stenosis 55.1 (14.6%), P < 0.001] and increased myocardial stiffness during dobutamine in the long-segment aortic stenosis group [Sham -26.0 (12.9%), CoA suture -27.5 (15.9%), CoA stenosis -9.5 (8.6%), stent -23.4 (4.8%), stent stenosis 19.9 (23.1%), P < 0.001]. Conclusions: This animal study on the sequelae of coarctation repair demonstrated that aortic stiffness had little effect on aortic pressure-flow characteristics in the absence of stenosis. However, the negative chronic effect of stenosis on aortic haemodynamics-especially a longer segment-leads to the rapid impairment of ventriculo-arterial interaction, which is accentuated by inotropy. Therefore, therapeutical management needs to focus on improving aortic remodelling after coarctation repair, preferably by minimizing residual stenosis, even at the cost of inducing aortic stiffness

Comparison of point-of-care tests, Sonoclot and PFA to asses coagulation: healthy volunteers vs normal pregnant patients

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Postmortem pump-driven reperfusion of the vascular system of porcine lungs: towards a new model for surgical training

PURPOSE: The objective of this experiment is to establish a continuous postmortem circulation in the vascular system of porcine lungs and to evaluate the pulmonary distribution of the perfusate. This research is performed in the bigger scope of a revascularization project of Thiel embalmed specimens. This technique enables teaching anatomy, practicing surgical procedures and doing research under lifelike circumstances. METHODS: After cannulation of the pulmonary trunk and the left atrium, the vascular system was flushed with paraffinum perliquidum (PP) through a heart-lung machine. A continuous circulation was then established using red PP, during which perfusion parameters were measured. The distribution of contrast-containing PP in the pulmonary circulation was visualized on computed tomography. Finally, the amount of leak from the vascular system was calculated. RESULTS: A reperfusion of the vascular system was initiated for 37 min. The flow rate ranged between 80 and 130 ml/min throughout the experiment with acceptable perfusion pressures (range: 37-78 mm Hg). Computed tomography imaging and 3D reconstruction revealed a diffuse vascular distribution of PP and a decreasing vascularization ratio in cranial direction. A self-limiting leak (i.e. 66.8% of the circulating volume) towards the tracheobronchial tree due to vessel rupture was also measured. CONCLUSIONS: PP enables circulation in an isolated porcine lung model with an acceptable pressure-flow relationship resulting in an excellent recruitment of the vascular system. Despite these promising results, rupture of vessel walls may cause leaks. Further exploration of the perfusion capacities of PP in other organs is necessary. Eventually, this could lead to the development of reperfused Thiel embalmed human bodies, which have several applications

O2 delivery and CO2 production during cardiopulmonary bypass as determinants of acute kidney injury: time for a goal-directed perfusion management?

Introduction: Acute kidney injury (AKI) is common after cardiac operations. There are different risk factors or determinants of AKI, and some are related to cardiopulmonary bypass (CPB). In this study, we explored the association between metabolic parameters (oxygen delivery (DO(2)) and carbon dioxide production (VCO(2))) during CPB with postoperative AKI. Methods: We conducted a retrospective analysis of prospectively collected data at two different institutions. The study population included 359 adult patients. The DO(2) and VCO(2) levels of each patient were monitored during CPB. Outcome variables were related to kidney function (peak postoperative serum creatinine increase and AKI stage 1 or 2). The experimental hypothesis was that nadir DO(2) values and nadir DO(2)/VCO(2) ratios during CPB would be independent predictors of AKI. Multivariable logistic regression models were built to detect the independent predictors of AKI and any kind of kidney function damage. Results: A nadir DO2 level < 262 mL/minute/m(2) and a nadir DO(2)/VCO(2) ratio < 5.3 were independently associated with AKI within a model including EuroSCORE and CPB duration. Patients with nadir DO(2) levels and nadir DO(2)/VCO(2) ratios below the identified cutoff values during CPB had a significantly higher rate of AKI stage 2 (odds ratios 3.1 and 2.9, respectively). The negative predictive power of both variables exceeded 90%. The most accurate predictor of AKI stage 2 postoperative status was the nadir DO(2) level. Conclusions: The nadir DO(2) level during CPB is independently associated with postoperative AKI. The measurement of VCO(2)-related variables does not add accuracy to the AKI prediction. Since DO(2) during CPB is a modifiable factor (through pump flow adjustments), this study generates the hypothesis that goal-directed perfusion management aimed at maintaining the DO(2) level above the identified critical value might limit the incidence of postoperative AKI

Acute and critically ill peripartum cardiomyopathy and 'bridge to' therapeutic options: a single center experience with intra-aortic balloon pump, extra corporeal membrane oxygenation and continuous-flow left ventricular assist devices

Introduction: Peripartum cardiomyopathy (PPCM) patients refractory to medical therapy and intra-aortic balloon pump (IABP) counterpulsation or in whom weaning from these therapies is impossible, are candidates for a left ventricular assist device (LVAD) as a bridge to recovery or transplant. Continuous-flow LVADs are smaller, have a better long-term durability and are associated with better outcomes. Extra corporeal membrane oxygenation (ECMO) can be used as a temporary support in patients with refractory cardiogenic shock. The aim of this study was to evaluate the efficacy and safety of mechanical support in acute and critically ill PPCM patients. Methods: This was a retrospective search of the patient database of the Ghent University hospital (2000 to 2010). Results: Six PPCM-patients were treated with mechanical support. Three patients presented in the postpartum period and three patients at the end of pregnancy. All were treated with IABP, the duration of IABP support ranged from 1 to 13 days. An ECMO was inserted in one patient who presented with cardiogenic shock, multiple organ dysfunction syndrome and a stillborn baby. Two patients showed partial recovery and could be weaned off the IABP. Four patients were implanted with a continuous-flow LVAD (HeartMate II(R), Thoratec Inc.), including the ECMO-patient. Three LVAD patients were successfully transplanted 78, 126 and 360 days after LVAD implant; one patient is still on the transplant waiting list. We observed one peripheral thrombotic complication due to IABP and five early bleeding complications in three LVAD patients. One patient died suddenly two years after transplantation. Conclusions: In PPCM with refractory heart failure IABP was safe and efficient as a bridge to recovery or as a bridge to LVAD. ECMO provided temporary support as a bridge to LVAD, while the newer continuous-flow LVADs offered a safe bridge to transplant