Non-Newtonian Patient-specific Simulations of Left Atrial Hemodynamics

Atrial fibrillation (AF) is the most common arrhythmia, affecting ~35M people worldwide. The irregular beating of the left atrial (LA) caused by AF impacts the LA hemodynamics increasing the risk of thrombosis and ischemic stroke. Most LA thrombi appear in its appendage (LAA), a narrow sac of varied morphology where blood is prone to stagnate. In the LAA, the combination of slow blood flow and low shear rates (<100 [1/s]) promotes the formation of red blood cell aggregations called rouleaux. Blood experiences a non-Newtonian behavior when rouleaux formed that has not been considered in previous CFD analysis of the LA. We model the anatomy and motion of the LA from 4D-CT images and solve the blood flow inside the LA geometry with our CFD in-house code, which models Non-Newtonian rheology with the shear-hematocrit-dependent Carreau-Yasuda equation. We cover a wide range of non-Newtonian effects considering a small and a large hematocrit, including an additional constitutive relation to account for themrouleaux formation time, and we compare our results with Newtonian simulations. Blood rheology influence in LAA hemostasis is studied in 6 patient-specific anatomies. Two subjects had an LAA thrombus (digitally removed before running the simulations), another had a history of TIAs, and the remaining three had normal atrial function. In our simulations, the shear rate remains below 50 [1/s] in the LAA for all non-Newtonian models considered. This triggers an increase of viscosity that alters the flow behavior in that site, which exhibits different flow patterns than Newtonian simulations. These hemodynamic changes translate into differences in the LAA hemostasis, calculated with the residence time.

Phenotypic Differences in a PRPH2 Mutation in Members of the Same Family Assessed with OCT and OCTA

Choroidal dystrophies comprise a group of chorioretinal degenerations. However, the different findings observed among these patients make it difficult to establish a correct clinical diagnosis. The objective of this study was to characterize new clinical findings by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in these patients. Four family members with a PRPH2 gene mutation (p.Arg195Leu) were included. OCT was performed at the macula, and the thickness of the outer and inner retina, total retina, and choroid was measured. The features of the vascular network were analyzed by OCTA. Patients showed a decreased outer nuclear layer in the avascular area compared with the controls. Two patients presented greater foveal and parafoveal degeneration of the outer retina, whereas the most degenerated area in the rest was the perifovea. Disruption of the third outer band at the foveola is one of the first-altered outer bands. Slow blood flow areas or capillary dropout were main signs in the deep capillary plexus. Microaneurysms were frequently observed in less degenerated retinas. Vascular loops and intraretinal microvascular abnormalities (IRMAs) were present in the superficial plexus. Extensive degeneration of the choriocapillaris was detected. Phenotypic differences were found between patients: two showed central areolar choroidal dystrophy and the rest had extensive chorioretinal atrophy. These signs observed in OCT and OCTA can help to more appropriately define the clinical disease in patients with choroidal dystrophies.

Prognosis Effects of Interventional Therapy on Patients with Coronary Slow Flow: An Observational Cohort Study

Background: The phenomenon of slow coronary blood flow is common clinically and is related to the patient experiencing repeated chest distress. The mechanism of slow blood flow is still unclear, and the prognosis after combined interventional therapy is unknown. Therefore, we evaluated the role of interventional therapy in this part of the population through the results of a 2-year follow-up.Methods: A total of 4663 patients who underwent continuous coronary angiography (CAG) were identified. Those patients with primary slow coronary flow were included in the study (n=369). The population was then divided into the PCI group and the N-PCI group. CTFT is used to assess the severity of slow blood flow. The endpoint events were the occurrence of rehospitalization and out-of-hospital death within 2 years. The log-rank test, Kaplan-Meier method, and Cox regression were used to evaluate and analyze the final results.Results: A total of 36 patients were readmitted to hospital, and 14 died suddenly outside the hospital during the follow-up period. Among these patients, 6 and 2 patients comprised the PCI group, while 30 and 12 patients comprised the N-PCI group. Comparison of the two groups showed no significant superiority (15.1% vs 13%, P=0.73). In Cox regression analysis, high BMI (body mass index) was an independent predictor of adverse end events (P=0.024).Conclusions: Interventional therapy may not improve outcomes in patients with slow coronary blood flow. BMI plays an important role in the influence of prognosis. Further research is needed to investigate this conclusion.

Features of indicators of crus rheogram in practically healthy teenagers of different somatotypes

Norms for assessing the functional state of the peripheral vascular system are developed, as a rule, without regard to age, gender and somatotype. The purpose of the study is to establish features of the indicators of crus rheogram in practically healthy girls and boys of different somatotypes, residents of the Podillia region of Ukraine. Rheographic indicators of the cohort of 108 practically healthy girls aged from 12 to 15 years old and 103 boys aged from 13 to 16 years and 103, urban residents of the Podillia region of Ukraine, were determined using a cardiology computer diagnostic complex. Anthropometric survey was conducted in accordance with the scheme of V. V. Bunak (1941). To evaluate the somatotype of adolescents, the mathematical scheme of J. Carter and B. Heath (1990) was used. The statistical processing of the obtained results was carried out in the license package "Statistica 5.5" using nonparametric methods for evaluating the obtained results. As a result of the research, it was found that most of the amplitudes and some of the derived indicators of the crus rheogram in girls of the mesomorphic somatotype are significantly lower or tend to be smaller than those of other somatotypes, while the time of the rising part of the rheogram and the time of slow blood filling are significantly higher than at representatives of an ectomorphic somatotype. In boys of mesomorphic somatotype, the basic impedance and amplitude of the systolic wave and the average speed of fast and slow blood flow of the rheogram are significantly lower or tend to be lower than those of other somatotypes, while the time of the ascending part and fast blood flow of rheograms and the diastolic index are significantly greater than in the representatives of the ecto-mesomorphic somatotype. It has also been found that almost half of the amplitude and derivative indices are significantly higher in girls than in boys of corresponding somatotypes, and most of the time - on the contrary, in boys, than in girls of corresponding somatotypes. Thus, indicators of crus rheogram in practically healthy girls and boys of different somatotypes, inhabitants of the Podillia region of Ukraine have pronounced differences mainly between the representatives of mesomorphic and ectomorphic somatotypes. Established pronounced manifestations of sexual dimorphism of indicators of crus rheogram between adolescents of corresponding somatotypes.

Age and gender features of thigh rheogram indicators in practically healthy adolescents

According to many studies, the rheovasographic index of the thighs can detect slight changes in the vessels, do not constitute a critical inconvenience, but in advance indicate that more serious diseases of the lower limb are approaching. The purpose of the study is to determine the age and gender features of thigh rheogram indicators in practically healthy adolescents in the Podillia region of Ukraine. The rheographic parameters of the thighs of 103 practically healthy boys aged from 13 to 16 years old and 108 girls aged from 12 to 15 years, urban residents of the Podillia region of Ukraine, were determined using a cardiology computer diagnostic complex. The statistical processing of the obtained results was carried out in the license package “Statistica 5.5” using parametric and nonparametric methods for evaluating the obtained results. In 12-year-old girls, in comparison with other age groups, it was found that most of the amplitude indices (with the exception of the incisura amplitude), the time of the downstream part of the rheogram and the average speed of fast and slow blood flow are significantly higher, while the time of the rising part of the rheogram and fast and slow blood overflow and thumb vascular tone rates in most cases are significantly lower. In most cases, 13 and 14-year-old boys, compared to 15 and 16-year-old adolescents, the basic impedance and amplitude of the systolic wave, as well as most vascular tone rates and average slow-blood flow rates are significantly higher or tend to be higher. It has also been found that most of the time indicators (with the exception of slow blood flow time) in 14-year-old boys are significantly lower or tend to be lower than in other age groups of boys. When comparing rheogram data between boys and girls according to the calendar and biological age, the majority of amplitude and derivative indices, as well as the time of slow blood filling in 14 and 15-year-old girls, are significantly higher in girls. Boys have significantly higher values of the duration of the cardiac cycle and the time of the downstream part of the thigh rheogram, as well as all time and most indicators of vascular tone in 13-year-old boys than in 12-year-old girls. Thus, the expressed age and gender differences in the rheogram data of the thigh in practically healthy adolescents have been established.

Brain MRI: a useful tool for screening of hypertensive patients for silent cerebro-vascular damage

Background: Worldwide hypertension is an important public-health challenge because of its high frequency and concomitant risks of cardiovascular, renal, cerebrovascular disease and death. Current guidelines for the management of hypertension mainly recommend the search for preclinical damage to the heart and kidneys. However, extending this search to other organs, for instance the brain, might improve risk stratification, might optimize antihypertensive therapy and might, in the end help to further reduce the burden of disease attributable to hypertension.Methods: 84 consecutive hypertensive patients with no target organ damage were enrolled in study to find out silent brain damage over a period of one year.Results: Mean body mass index (BMI) of the study population was 28.4±2.5 kg/m2 (range 23.2 to 35.3kg/m2). 33 (39.3%) subjects had white matter lesions. 13 (15.47%) study subjects were found to have vascular changes which included micro angiopathic changes, infarcts and reduced/slow blood flow. 33 (39.3%) subjects were found to have normal brain MRI in the study. Early brain MRI was found to be beneficial in patients who had uncontrolled blood pressure either due to lack of treatment or irregular use of anti-hypertensive treatment. This was true for every age group in general and particularly in subjects above the age of 50 years.Conclusions: The screening of hypertensive patients for silent cerebrovascular damage with brain MRI may be useful in stratifying the risk of future cerebrovascular disease.