The arterial network in healthy young adults is thought to be structured to minimise wave reflection in conduit arteries, producing an ascending aortic pressure waveform with three key features: early systolic peak, negative systolic augmentation, and diastolic hump. One-dimensional computer models have provided significant insights into arterial haemodynamics, but no previous models of the young adult have exhibited these three features. Since the latter was likely to be related to unrepresentative or non-optimised impedance properties of the model arterial networks, we developed a new ‘YoungAdult’ model that incorporated 1) a novel and more accurate empirical equation for approximating wave speeds, based on area and relative distance to elastic-muscular arterial transition points, 2) optimally-matched arterial junctions, and 3) an improved arterial network geometry that eliminated ‘within-segment’ taper (which causes wave reflection in conduit arteries) whilst establishing ‘impedance-preserving’ taper. These model properties led to wave reflection occurring predominantly at distal vascular beds, rather than in conduit arteries. The model predicted all three typical characteristics of an ascending aortic pressure waveform observed in young adults. When compared with non-invasively acquired pressure and velocity measurements (obtained via tonometry and Doppler ultrasound in 7 young adults), the model was also shown to reproduce the typical waveform morphology observed in the radial, brachial, carotid, temporal, femoral, and tibial arteries. The YoungAdult model provides support for the concept that the arterial tree impedance in healthy young adults is exquisitely optimised, and it provides an important baseline model for investigating cardiovascular changes in ageing and disease states.

Background: Along with sarcopenia, delayed blood pressure (BP) recovery after standing and orthostatic hypotension (OH) are among key clinical challenges associated with ageing. Previous studies have reported an association between sarcopenia and delayed orthostatic BP recovery and OH. However, the haemodynamic mechanisms underlying this association remain unclear. Methods: 107 attendees to a falls and syncope clinic aged 50+ years underwent an active stand test with non-invasive beat-to-beat haemodynamic measurement. Hand grip strength and 5-chair stands time were measured. Muscle mass was estimated using bioelectrical impedance analysis, and participants were classified as non-sarcopenic and sarcopenic. Mixed effects models with linear splines were used to model the effect of sarcopenia status on Modelflow®-derived mean arterial pressure (MAP), cardiac output (CO), total peripheral resistance (TPR), stroke volume (SV) and heart rate (HR) after standing, while controlling for potential confounders. Results: Sarcopenia was associated with: attenuated recovery of MAP in the 10-20s period after standing (β -0.67, P<0.001); attenuated rise to peak (0-10s) and recovery from peak (10-20s) of CO (β -0.05, P<0.001; β 0.06, P<0.001); attenuated recovery (10-20s) of TPR from nadir (β -0.02, P<0.001) and attenuated recovery from peak (10-20s) of SV (β 0.54, P<0.001). HR was not significantly associated with sarcopenia status at any time interval after standing. Conclusion: The attenuated BP recovery after standing seen in sarcopenia appears to be driven by initial diminished peak of CO followed by attenuated recovery of CO from peak and TPR from nadir. The CO finding appears to be driven by SV rather than HR. Potential mechanisms for these findings include: cardio-sarcopenia, the effects of sarcopenia on the autonomic nervous system and/or the skeletal muscle pump.

Haemodynamic simulations are increasingly used to study vascular diseases like Intracranial Aneurysms (IA) and to further develope treatment options. However, due to limited data, some aspects must rely on heuristics, especially at the simulation’s distal ends. In literature, Murray’s Law is often used to model the outflow split based on vessel cross-section area, but this poses challenges for the communicating arteries in the Circle of Willis (CoW). In this study, we contribute by assessing the impact of Murray’s Law in patient-specific geometries featuring IA at the posterior communication. We simulate different domain extensions, representing common modelling choices. We establish Full CoW simulations as a baseline to evaluate the effect of these modelling assumptions on haemodynamic indicators, focusing on IA growth and rupture-related factors like Wall Shear Stress (WSS) and Oscillatory Shear Index (OSI). Our findings reveal qualitative alterations in haemodynamics when not modeling posterior communication. Comparisons between computing the anterior circulation and computing the whole Circle of Willis reveal quantitative changes in WSS may reach up to 80%, highlighting the significance of modelling choices in assessing IA risks and treatment strategies.

Haemodynamic indices are widely used in clinical practice for deciding on a particular type of treatment. Low quality of the CT data and tachycardia complicate interpretation of the measured or simulated values. In this work, we present a novel approach for evaluating resistances in terminal coronary arteries. Using 14 measurements from 10 patients, we show that this algorithm retains the accuracy of 1D haemodynamic simulations in less detailed (truncated) geometric models of coronary networks. We also apply the variable systole fraction model to study the effect of elevated heart rate on the values of FFR, CFR and iFR. We conclude that tachycardia may produce both overestimation or underestimation of coronary stenosis significance.

Background: Kidney transplantation is considered the first-choice therapy in ESRD patients. Despite recent improvements in terms of outcomes and graft survival in recipients, postoperative complications still concern health-care providers involved in the management of those patients. Particularly challenging are cardiovascular complications. Perioperative goal-directed fluid-therapy (PGDT) and hemodynamic optimization are widely used in high-risk surgical patients, and are associated with a significant reduction in postoperative complication rates and length of stay (LOS). The aim of this work is to compare the effects of perioperative goal-directed therapy (PGDT) with conventional fluid therapy (CFT), and to determine whether there are any differences in major postoperative complications rates and delayed graft function (DGF) outcomes. Methods: Prospective study with historical controls. Two groups, a PGDT- and a CFT- group were used: the stroke volume (SV) optimization protocol was applied in PGDT group throughout the procedure. Conventional fluid therapy with fluids titration at a central venous pressure (CVP) 8-12 mmHg and mean arterial pressure (MAP) >80mmHg was applied to the control-group. Postoperative data collection including vital signs, weight, urinary output, serum creatinine, blood urea nitrogen, serum potassium, and assessement of volemic status and the signs and symptoms of major postoperative complications occurred at 24h, 72h, 7 days and 30 days after transplantation. Results: Among the 66 patients enrolled, 33 were in each group and both groups had similar physical characteristics. Good fuctional recovery was evident in the 94% of patients. The statistical analysis has showed a difference in postoperative complications as follows: significant reduction of cardiovascular complications, DGF episodes (p<0.05) and surgical complications (p<0.01). There were no significant differences in pulmonary or other complication. Conclusions: PGDT and SV optimization effectively influenced the rate of major postoperative complications, reducing the overall morbidity and thus the mortality in patients receiving kidney transplantation.