Repeated 15-minute coronary occulsions in pigs increase occlusion arrhythmias but decrease reperfusion arrhythmias that are associated with extracellular hypokalemia

AbstractObjectives. We sought to evaluate the effects of repetitive 15-min coronary occlusions followed by 45-min reperfusions on the incidence of occlusion and reperfusion arrhythmias in pigs.Background. Brief 2- to 5-min coronary occlussions seem to exert a protective effect on occlusion and reperfusion arrhythmias. However, because clinical ischemic episodes are often longer, it would be appropriate to assess whether such protection also occurs when longer cycles of occlusion-reperfusion are produced.Methods. Three to four cycles of 15-min coronary occlusions with 45-min reperfusions were performed in 34 pigs, and changes in ST segment and incidence of ventricular arrhythmias were assessed. Plasma potassium ion concentrations in eight pigs and blood gas in six were measured from blood from the ischemic area during reperfusion.Results. Repetitive occlusions were associated with a progressively higher ST segment elevation and a higher incidence of ST segment alternans (p < 0.001) and ventricular fibrillation (VF) (p < 0.01). However, during repetitive reperfusions, normalization of the ST segment was increasingly faster, the incidence of VF was progressively reduced (p < 0.03), and there was progressively less severe regional acidosis ([mean ± SD] 7.06 ± 0.12 vs 7.26 ± 0.06, p < 0.05) and hypokalemia (1.9 ± 0.7 vs. 2.3 ± 0.4 mEq/liter, p = NS).Conclusions. The progressive electrocardiographic deterioration and increasing incidence of ventricular arrhythmias during repetitive 15-min occlusions in pigs suggest increasing metabolic derangement. However, the progressively faster normalization of the ST segment and the reduced incidence of ventricular arrhythmias during reperfusion suggest an increasingly faster restoration of the metabolic and ionic balance

Simplifying the verification of simulation models through Petri net to FlexSim mapping

Simplifying the encoding of a simulation conceptual model representation reduces the number of errors that will be detected in the verification phase. In this paper, we present a mapping between Petri nets, a well-known formalism, and FlexSim, a well-known simulation tool. The proposal is illustrated through an example of how a model specified in a Petri net can be encoded easily, reducing the time needed to understand and verify the model. In the proposed methodology, the mapping must be defined at the initial stage of the encoding, starting from (in this case) a Petri net conceptual model, and ending at the encoding tool (FlexSim in this case). The main advantages of the proposed methodology are discussed.Peer ReviewedPostprint (author's final draft

Simulation and optimization for an experimental environment to wildfire resource management and planning: firefight project modelling and architecture

Firefighting resource management is crucial to contain and extinguish wildfires. Resource optimization in wildfire containment can help to reduce the dangers and risks to both human (firemen and area inhabitants) and natural environment. The use of simulation to predict wildfire evolution combined with optimization techniques can lead to an optimal resource deployment and management to minimize natural and human risks. This article proposes a simulation and optimization architecture; a well-defined data format to represent firefighting resources and an experimental platform to simulate wildfire spread, wildfire containment, resource dispatching and management and resource optimization. The simulation and optimization environment will be tested in the Catalonia region (Spain) in collaboration with Catalan Firefight Department.Peer ReviewedPostprint (author’s final draft

Corneal transplantation activity in Catalonia, Spain, from 2011 to 2018: evolution of indications and surgical techniques.

Purpose: To report corneal transplant activity carried out in Catalonia (Spain) and the evolving indications for keratoplasty over an 8-year period. Methods: Annual reports from the Catalan Transplant Organization, Spain, on corneal graft indications and techniques from 2011 to 2018 were reviewed. Results: A total of 9457 keratoplasties were performed in Catalonia, from January 2011 to December 2018. The most frequent indications were bullous keratopathy (BK; 20.5%), Fuchs endothelial dystrophy (FED; 17.9%), re-graft (13.7%), and keratoconus (11.3%). Penetrating keratoplasty (PKP) accounted for 63.4% of all performed keratoplasties. Since the introduction of eye bank precut tissue for Descemet stripping automated endothelial keratoplasty (DSAEK) in 2013 and for Descemet membrane endothelial keratoplasty (DMEK) in 2017 the number of endothelial keratoplasties has drastically increased. An increasing trend of posterior lamellar techniques over the total of keratoplasties was found (p<0.001). Endothelial keratoplasties for different endothelial diseases indications (BK, FED, and re-graft), also showed and increasing trend (p<0.001). DMEK is the technique with the highest increase (statistically significantly different from linearity) over other endothelial keratoplasties in FED (p<0.001) but not in BK (p = 0.67) or re-grafts (p = 0.067). Conclusion: Endothelial diseases represented the top indication for keratoplasty over the 8-year period. PKP is still the most used technique in Catalonia, but endothelial keratoplasties and especially DMEK showed a significant increasing trend over the last years. This is congruent withthe main rationale nowadays for keratoplasties: to customize and transplant as less tissue as possible. Therefore, the availability of precut tissue could have definitely enforced such approach

Prothrombotic profile in patients with vasospastic or non vasospastic angina and non significant coronary stenosis

Background: Patients with vasospastic (VA) or non vasospastic angina (NVA) without significant coronary stenosis have a reduced risk of infarction but is unclear whether or not this may be attributable to a lack of prothrombotic profile - similar to that present in patients with stable coronary artery disease (CAD). Methods: Plasma levels of von Willebrand factor, total and free tissue factor pathway inhibitor, plasminogen activator inhibitor-1, and fibrinogen were analyzed in 15 patients with stable VA and 23 with NVA, all with vasoconstrictive response to acetylcholine although with different severity. Results were compared with those of 20 age-matched controls and 10 patients with CAD. Results: Plasma levels of von Willebrand factor in patients with VA or NVA were higher than in controls (207 ± 62 and 203 ± 69% vs 121 ± 38%, p < 0.001) and tended to be lower than in CAD patients (264 ± 65, p = 0.145). They also presented higher total tissue factor pathway inhibitor (123 ± 18 and 111 ± 25 vs 88 ± 14, ng/ml p < 0.001) and plasminogen activator inhibitor-1 levels than controls (51 ± 30 and 52 ± 31% vs 19 ± 9 ng/ml, p < 0.001) and similar to CAD patients (134 ± 23 and 62 ± 31, respectively, ns). Moreover, free tissue factor pathway inhibitor plasma levels were lower than controls (18 ± 5 and 17 ± 5 vs 23 ± 8 ng/ml, p = 0.002) and similar to CAD patients (14 ± 5, ns). Despite this prothrombotic condition none of VA or NVA patients presented a myocardial infarction during a 9 year follow-up, an observation also reported in larger series. Conclusions: During a stable phase of their disease, patients with VA or NVA present a prothrombotic profile that might eventually contribute to occurrence of myocardial infarction. The rarity of these events, however, may suggests that ill defined factors would protect these patients from coronary plaque rupture/fissure