In the chronic stage of myocardial infarction, a significant number of patients develop life-threatening ventricular tachycardias (VT) due to the arrhythmogenic nature of the remodeled myocardium. Radiofrequency ablation (RFA) is a common procedure to isolate reentry pathways across the infarct scar that are responsible for VT. Unfortunately, this strategy show relatively low success rates; up to 50% of patients experience recurrent VT after the procedure. In the last decade, intensive research in the field of computational cardiac electrophysiology (EP) has demonstrated the ability of three-dimensional (3D) cardiac computational models to perform
in-silico
EP studies. However, the personalization and modeling of certain key components remain challenging, particularly in the case of the infarct border zone (BZ). In this study, we used a clinical dataset from a patient with a history of infarct-related VT to build an image-based 3D ventricular model aimed at computational simulation of cardiac EP, including detailed
patient-specific
cardiac anatomy and infarct scar geometry. We modeled the BZ in eight different ways by combining the presence or absence of electrical remodeling with four different levels of image-based patchy fibrosis (0, 10, 20, and 30%). A 3D torso model was also constructed to compute the ECG.
Patient-specific
sinus activation patterns were simulated and validated against the patient's ECG. Subsequently, the pacing protocol used to induce reentrant VTs in the EP laboratory was reproduced
in-silico
. The clinical VT was induced with different versions of the model and from different pacing points, thus identifying the slow conducting channel responsible for such VT. Finally, the real patient's ECG recorded during VT episodes was used to validate our simulation results and to assess different strategies to model the BZ. Our study showed that reduced conduction velocities and heterogeneity in action potential duration in the BZ are the main factors in promoting reentrant activity. Either electrical remodeling or fibrosis in a degree of at least 30% in the BZ were required to initiate VT. Moreover, this proof-of-concept study confirms the feasibility of developing 3D computational models for cardiac EP able to reproduce cardiac activation in sinus rhythm and during VT, using exclusively non-invasive clinical data.
Poly(vinyl alcohol)-based proton-conducting membranes, due to their high selectivity for water with respect to alcohols, have been suggested as a promising alternative to perfluorinated ionomer, Nafion V R , widely used as an electrolyte in hydrogen (PEMFC) and direct methanol (DMFC) fuel cells. Sulfosuccinic acid (SSA) has been commonly used as a crosslinking agent to form an inter-crosslinked structure and a promoting sulfonating agent to enhance the ion conductivity. The introduction of SSA increases proton conductivity of PVA-based polymer electrolyte membranes and reduces methanol permeability. Crosslinking produces deep changes in the crystallinity of PVA membranes and also alters the state and content of water in the membrane. In addition, the presence of the protonic acid promotes the appearance of degradation reactions at temperatures well below those of unmodified PVA, thus producing a decrease in thermal and mechanical stability. In this work, the thermal and mechanical properties of membranes prepared using PVA with different proportions of SSA were investigated by calorimetry and mechanical thermal analysis. The results indicate that the crystallinity disappears in membranes containing 2% of SSA or more. As a result of the combined effect of the disappearance of crystallinity and the increase of crosslinking, the equilibrium water content first increases (up to 5% SSA) but at higher proportions of SSA it decreases. Above 100 C, the amorphous membranes undergo degradation reactions such as the elimination of lateral OH groups of PVA and the formation of polyene structures, making the membrane colored, brittle and crackly.
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