Short-term fluctuations in the concentration of cortisol and progesterone in fetal plasma, maternal plasma, and amniotic and allantoic fluids from sheep during late pregnancy

Fluctuations in the concentrations of cortisol and progesterone in fetal plasma, maternal plasma, and amniotic and allantoic fluids were measured in samples taken at 10-min intervals over a 90-min period from three groups of sheep sampled at different times during late pregnancy. During the last 30 days of gestation there was a significant rise in the mean concentration of cortisol in fetal plasma and amniotic fluid and a significant correlation between the cortisol concentration in these two fluids. The concentration of cortisol in allantoic fluid exceeded that in amniotic fluid. The concentration of cortisol in fetal plasma varied in a pulsatile manner, however the coefficient of variation (CV) within animals was greater (36%) on days -11 to -20, relative to the day of parturition (day 0), than on days -21 to -30 or days -5 to 0(15-19%). The CV values for cortisol in amniotic fluid and maternal plasma during the last 30 days of pregnancy were 20-50% and two at five times greater than the intraassay CV. The concentration of progesterone in amniotic fluid increased after day -20 but was not correlated with that in maternal plasma or fetal plasma. The concentrations of progesterone in paired samples of amniotic fluid and allantoic fluid were similar. The CV values for progesterone (18-34%) were similar in fetal and maternal plasma and amniotic fluid and did not change significantly during late pregnancy. Changes in the concentration of progesterone were unrelated to changes in cortisol. Interpretation of steroid profiles in fetal plasma and fluids through late pregnancy should take into account these short-term fluctuations in hormone concentrations.

An in silico analysis of heart rate impact on wall shear stress hemodynamic parameters in aortic coarctation

This study examines how heart rate (HR) affects hemodynamics in a South African infant with Coarctation of the Aorta. Computed tomography angiography segments aortic coarctation anatomy; Doppler echocardiography derives inlet flow waveforms. Simulations occur at 100, 120, and 160 beats per minute, representing reduced, resting, and elevated HR levels. Turbulence was analyzed over time and space using turbulence-resolving and pulsatile large-eddy simulations. Specifically, a 60% reduction in HR led to a reduction in maximum velocity by 45%, and a 57% decrease in pressure drop. The reduction in turbulence-related metrics was less significant. The ratio of turbulent kinetic energy to total kinetic energy decreased by 2%, while turbulent wall shear stress decreased by 3%. These results demonstrate that HR significantly affects velocity and pressure drop, while turbulence arising from the coarctation region is relatively unaffected. The balance between turbulent kinetic energy and total kinetic energy shows minimal enhancement due to the complex interplay among HR, turbulence, and geometry. This complexity prompts discussion on how HR-slowing medications, such as beta-blockers or ivabradine, could positively influence hemodynamic stresses. In particular, the results indicate that while HR modulation can influence flow dynamics, it may not significantly reduce turbulence-induced shear stresses within the coarctation zone. Therefore, further investigation is necessary to understand the potential impact of HR modulation in the management of CoA, and whether interventions targeting the anatomical correction of the coarctation may be more effective in improving hemodynamic outcomes.

Growth in a two-dimensional model of coarctation of the aorta: A CFD-informed agent based model

In the individualized treatment of a patient with Coarctation of the Aorta (CoA), a non-severe case which initially exhibits no symptoms, and thus requires no treatment, could potentially become severe over time. This progression can be attributed to insufficient growth at the coarctation site relative to the overall growth of the child. Therefore, an agent-based model (ABM) to predict the aortic growth of a CoA patient is introduced. The multi-scale approach combines Computational Fluid Dynamics (CFD) and ABM to study systems that are influenced by both mechanical stimuli and biochemical responses characteristic of growth. Our focus is on ABM development; thus, CFD insights were applied solely to enhance the ABM framework. Comparative medicine was leveraged to develop a species-specific ABM by considering the rat and porcine species commonly used in cardiovascular research together with data from healthy human toddlers. The ABM luminal radius prediction accuracy was observed to be 79% for rat, above 95% for porcine and 91. 6% for the healthy toddler; while that observed for the growth rate was 38.7%, 90% and 64.3% respectively. Given its performance, the ABM was adapted to a 2.5-year-old patient-specific CoA. Subsequently, the model predicted that by age 3, the condition would worsen, marked by persistent CoA enhanced by the predicted least growth compared to growth predicted in the rest of the aorta, hypertension, and increased turbulent flow; thus, increased vessel injury risk. The findings advise for incorporating vascular remodelling into the ABM to enhance its predictive capability for intervention planning.