No abstract

Cardiovascular surgery requires the use of state-of-the-art artificial materials. For example, microporous polytetrafluoroethylene grafts manufactured by Gore-Tex® are used for the treatment of cyanotic heart defects (i.e., modified Blalock–Taussig shunt). Significant mortality during this palliative operation has led surgeons to adopt mathematical models to eliminate complications by performing fluid–solid interaction (FSI) simulations. To proceed with FSI modeling, it is necessary to know either the mechanical properties of the aorta and graft or the rheological properties of blood. The properties of the aorta and blood can be found in the literature, but there are no data about the mechanical properties of Gore-Tex® grafts. Experimental studies were carried out on the mechanical properties vascular grafts adopted for modified pediatric Blalock–Taussig shunts. Parameters of two models (the five-parameter Mooney–Rivlin model and the three-parameter Yeoh model) were determined by uniaxial experimental curve fitting. The obtained data were used for patient-specific FSI modeling of local blood flow in the “aorta-modified Blalock–Taussig shunt–pulmonary artery” system in three different shunt locations: central, right, and left. The anisotropic model of the aortic material showed higher stress values at the peak moment of systole, which may be a key factor determining the strength characteristics of the aorta and pulmonary artery. Additionally, this mechanical parameter is important when installing a central shunt, since it is in the area of the central anastomosis that an increase in stress on the aortic wall is observed. According to computations, the anisotropic model shows smaller values for the displacements of both the aorta and the shunt, which in turn may affect the success of preoperative predictions. Thus, it can be concluded that the anisotropic properties of the aorta play an important role in preoperative modeling.

Objective. To study the possibility of using N-terminal pro-BNP fragment as a screening criterion of hemodynamic significant of the functioning arterial duct in extremely premature newborns. Hemodynamically significant functioning arterial duct (HSFAD) is a reason of the development of various complications in extremely premature newborns. The basic method for HSFAD diagnosis is Echo CG. The limited technical abilities of ultrasound devices can prevent from an early diagnosis and timely treatment of this state. The search of additional markers of hemodynamic significance the functioning arterial duct (FAD) is actual. Materials and methods. A continuous prospective observational study included patients aged 1 to 3 days with FAD, gestation period of 2532 weeks and birth weight from 500 to 1500 g. Hemodynamic significance of FAD was determined according to generally accepted Eco CG criteria. The level of NT-pro-BNP was identified with IFA on the third day of life. Mathematical modelling was used to calculate a threshold value of NT-pro-BNP, corresponding to 6500 pg/ml, at which the probability of hemodynamic significance of the functioning arterial duct exceeds 80 %. Results. The assessment of NT-pro BNP concentration on the third day of life permitted to establish the following reliable differences: in the main group, the median concentration for NT-pro BNP was 15000 [IQR 2 587; 26 500] pg/ml, in the comparison group 1920 [IQR 1379; 3467] pg/ml, р = 0.001. Mean force direct correlation, r = 0.52, between Echo CG results and NT-pro-BNP values was stated. Conclusions. The obtained results make it possible to use NT-pro-BNP as a screening criterion of FAD hemodynamic significance in extremely premature newborns.

Hemodynamically significant patent ductus arteriosus (hsPDA) in premature newborns is associated with a risk of PDA-related morbidities. Classification into risk groups may have a clinical utility in cases of suspected hsPDA to decrease the need for echocardiograms and unnecessary treatment. This prospective observational study included 99 premature newborns with extremely low body weight, who had an echocardiogram performed within the first three days of life. Discriminant analysis was utilized to find the best combination of prognostic factors for evaluation of hsPDA. We used binary logistic regression analysis to predict the relationship between parameters and hsPDA. The cohort’s mean and standard deviation gestational age was 27.6 ± 2.55 weeks, the mean birth weight was 1015 ± 274 g. Forty-six (46.4%) infants had a PDA with a mean diameter of 2.78 mm. Median NT-pro-BNP levels were 17,600 pg/mL for infants with a PDA and 2773 pg/mL in the non-hsPDA group. The combination of prognostic factors of hsPDA in newborns of extremely low body weight on the third day of life was determined: NT-pro-BNP, Apgar score, Silverman–Anderson score (Se = 82%, Sp = 88%). A cut-off value of NT-pro-BNP of more than 8500 pg/mL can predict hsPDA (Se = 84%, Sp = 86%).

<p>Surgical treatment of congenital heart defects with the obstruction of the outflow tract of the right ventricle can be performed in several stages. The first stage of surgical correction is the creation of a systemic-pulmonary shunt, followed by radical correction. The main complications of systemic-pulmonary shunts are associated with the development of shunt thrombosis and hypervolemia of the pulmonary circulation. Currently, considering the importance of individual selection of a shunt for effective functioning, the main scientific search is aimed at creating optimal methods that consider all the hemodynamic features of a particular patient. Recently, the direction of mathematical modelling and biomechanical analysis in medicine has been actively developing, facilitating the objective evaluation of the accumulated clinical experience and is one of the main tools in evidence-based medicine. The use of computational fluid dynamics methods for modified Blalock–Taussig shunt analysis allows us evaluate the hemodynamic parameters for various configurations of shunts and anastomosis angles and improve the understanding of pathophysiological processes in the cardiovascular system before or after an application of the modified Blalock–Taussig shunt. Here, we provide an overview of the work related to the use of modelling for the calculation of the currents in the aorta–shunt–pulmonary artery system. It is noteworthy that most studies consider the personalised characteristics of the patients and are therefore highly likely to be used in clinical practice. The main hemodynamic parameters that are analysed with the computer calculations are described. Part of the work is devoted to the stages of computer modelling and the limitations in the implementation of these stages. We believe that this manuscript will be of interest to specialists in cardiovascular surgery and to the several scholars working in areas related to the use of digital technologies in medicine, mathematical modelling in medicine and biomechanics.</p><p>Received 30 January 2020. Revised 25 May 2020. Accepted 9 June 2020.</p><p><strong>Conflict of interest:</strong> Authors declare no conflict of interest.</p><p><strong>Funding:</strong> The work is supported by the program for the development of the Scientific and Educational Mathematical Center of the Volga Federal District (No. 075-02-2020-1478) and a grant for the development of the scientific school of the Perm Region “Computer biomechanics and digital technologies in biomedicine”.</p><p><strong>Author contributions</strong><br />Conception and design: Yu.S. Sinelnikov, V.B. Arutunyan, A.A. Porodikov, A.N. Biyanov, V.S. Tuktamyshev, M.I. Shmurak,<br />A.R. Khairulin<br />Drafting the article: A.A. Porodikov, A.N. Biyanov, A.G. Kuchumov<br />Critical revision of the article: A.N. Biyanov, A.G. Kuchumov<br />Final approval of the version to be published: Yu.S. Sinelnikov, V.B. Arutunyan, A.A. Porodikov, A.N. Biyanov, V.S. Tuktamyshev, M.I. Shmurak, A.R. Khairulin, A.G. Kuchumov</p>