Non-alcoholic fatty liver disease is associated with coronary flow reserve impairment: A pilot meta-analysis.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is estimated to affect approximately 25% of the global population. Both, coronary artery disease and NAFLD are linked to underlying insulin resistance and inflammation as drivers of the disease. Coronary flow reserve parameters, including coronary flow reserve velocity (CFRV), baseline diastolic peak flow velocity (DPFV), and hyperemic DPFV, are noninvasive markers of coronary microvascular circulation. The existing literature contains conflicting findings regarding these parameters in NAFLD patients. METHODS: A comprehensive systematic search was conducted on major electronic databases from inception until May 8, 2024, to identify relevant studies. We pooled the standardized mean differences (SMD) with 95% confidence intervals (CI) using the inverse-variance random-effects model. Statistical significance was set at P < .05. RESULTS: Four studies with 1139 participants (226 with NAFLD and 913 as controls) were included. NAFLD was associated with a significantly lower CFRV (SMD: -0.77; 95% CI: -1.19, -0.36; P < .0002) and hyperemic DPFV (SMD: -0.73; 95% CI: -1.03, -0.44; P < .00001) than the controls. NAFLD demonstrated a statistically insignificant trend toward a reduction in baseline DPFV (SMD: -0.09; 95% CI: -0.38, 0.19; P = .52) compared to healthy controls. CONCLUSION: Patients with NAFLD are at a higher risk of coronary microvascular dysfunction, as demonstrated by reduced CFRV and hyperemic DPFV. The presence of abnormal coronary flow reserve in patients with NAFLD provides insights into the higher rates of cardiovascular disease in these patients. Early aggressive targeted interventions for impaired coronary flow reserve in subjects with NAFLD may lead to improvement in clinical outcomes.

Patient-specific compliant simulation framework informed by 4DMRI-extracted pulse wave Velocity: Application post-TEVAR.

We introduce a new computational framework that utilises Pulse Wave Velocity (PWV) extracted directly from 4D flow MRI (4DMRI) to inform patient-specific compliant computational fluid dynamics (CFD) simulations of a Type-B aortic dissection (TBAD), post-thoracic endovascular aortic repair (TEVAR). The thoracic aortic geometry, a 3D inlet velocity profile (IVP) and dynamic outlet boundary conditions are derived from 4DMRI and brachial pressure patient data. A moving boundary method (MBM) is applied to simulate aortic wall displacement. The aortic wall stiffness is estimated through two methods: one relying on area-based distensibility and the other utilising regional pulse wave velocity (RPWV) distensibility, further fine-tuned to align with in vivo values. Predicted pressures and outlet flow rates were within 2.3 % of target values. RPWV-based simulations were more accurate in replicating in vivo hemodynamics than the area-based ones. RPWVs were closely predicted in most regions, except the endograft. Systolic flow reversal ratios (SFRR) were accurately captured, while differences above 60 % in in-plane rotational flow (IRF) between the simulations were observed. Significant disparities in predicted wall shear stress (WSS)-based indices were observed between the two approaches, especially the endothelial cell activation potential (ECAP). At the isthmus, the RPWV-driven simulation indicated a mean ECAP>1.4 Pa-1 (critical threshold), indicating areas potentially prone to thrombosis, not captured by the area-based simulation. RPWV-driven simulation results agree well with 4DMRI measurements, validating the proposed pipeline and facilitating a comprehensive assessment of surgical decision-making scenarios and potential complications, such as thrombosis and aortic growth.

Cerebral, Splanchnic, and Renal Transit Time Measurement and Blood Volume Estimation Using Contrast-Enhanced Ultrasonography.

ABSTRACT: We aimed to measure cerebral, splanchnic, and renal transit times and the associated blood volumes using contrast ultrasound. In healthy individuals, regional transit times were calculated from time-intensity curves generated as ultrasound contrast passed through the associated inflow and outflow vessels. These included the internal carotid artery and internal jugular vein (brain), the superior mesenteric artery and portal vein (intestines), and the renal artery and renal vein (kidney). An organ's blood volume relative to the stroke volume delivered to that organ with each cardiac cycle was calculated from the product of heart rate and transit time of contrast passage through the associated vascular bed. The fraction of systemic stroke volume received by each organ was calculated from the respective velocity-time integral and inflow vessel cross-sectional area and used to estimate absolute organ blood volume. The cohort consisted of 16 participants (age: 42 ± 13 years; 5 female) without known cerebrovascular, gastrointestinal, or renal disease. Cerebral, splanchnic, and renal transit times were obtained for 15, 14, and 8 individuals, respectively. Anatomic variability of the renal vessels confounded the acquisition of renal transit times. For all organs, transit times were reproducible and the associated blood volumes were generally comparable to reference values. Cerebral, gastrointestinal, and renal transit times/blood volumes can be reasonably acquired from contrast ultrasound, although the latter is less reliably available. Assessment of the impact on regional blood volumes of pharmacologic or other interventions is a next step toward clinical application of this technique.

Plexus-Specific Retinal Capillary Blood Flow Analysis Using Erythrocyte Mediated Angiography and Optical Coherence Tomography Angiography.

Purpose: The purpose of this study was to identify and measure plexus-specific absolute retinal capillary blood flow velocity and acceleration in vivo in both nonhuman primates (NHPs) and humans using erythrocyte mediated angiography (EMA) and optical coherence tomography angiography (OCTA). Methods: EMA and OCTA scans centered on the fovea were obtained in 2 NHPs and 11 human subjects. Scans were also obtained in NHP eyes while IOP was experimentally elevated. Erythrocyte velocity and acceleration in retinal arteries, capillaries, and veins were measured and capillaries were categorized based on location within the superficial vascular (SVP), intermediate capillary (ICP), or deep capillary plexus (DCP). Generalized linear mixed models were used to estimate the effects of intraocular pressure (IOP) on capillary blood flow. Results: Capillary erythrocyte velocity at baseline IOP was 0.64 ± 0.29 mm/s in NHPs (range of 0.14 to 1.85 mm/s) and 1.55 ± 0.65 mm/s in humans (range of 0.46 to 4.50 mm/s). Mean erythrocyte velocity in the SVP, ICP, and DCP in NHPs was 0.69 ± 0.29 mm/s, 0.53 ± 0.22 mm/s, and 0.63 ± 0.27 mm/s, respectively (P = 0.14 for NHP-1 and P = 0.28 for NHP-2). Mean erythrocyte velocity in the human subjects did not differ significantly among SVP, ICP, and DCP (1.46 ± 0.59 mm/s, 1.58 ± 0.55 mm/s, and 1.59 ± 0.79 mm/s, P = 0.36). In NHPs, every 1 mm Hg increase in IOP was associated with a 0.13 mm/s reduction in arterial velocity, 0.10 mm/s reduction in venous velocity, and 0.01 mm/s reduction in capillary velocity (P < 0.001) when accounting for differences in mean arterial pressure (MAP). Conclusions: Blood flow by direct visualization of individual erythrocytes can be quantified within capillary plexuses. Capillary velocity decreased with experimental IOP elevation.

The effect of posture on the age dependence of neurovascular coupling.

Previous studies report contradicting age-related neurovascular coupling (NVC). Few studies assess postural effects, but less investigate relationships between age and NVC within different postures. Therefore, this study investigated the effect of age on NVC in different postures with varying cognitive stimuli. Beat-to-beat blood pressure, heart rate and end-tidal carbon dioxide were assessed alongside middle and posterior cerebral artery velocities (MCAv and PCAv, respectively) using transcranial Doppler ultrasonography in 78 participants (31 young-, 23 middle- and 24 older-aged) with visuospatial (VST) and attention tasks (AT) in various postures at two timepoints (T2 and T3). Between-group significance testing utilized one-way analysis-of-variance (ANOVA) (Tukey post-hoc). Mixed three-way/one-way ANOVAs explored task, posture, and age interactions. Significant effects of posture on NVC were driven by a 3.8% increase from seated to supine. For AT, mean supine %MCAv increase was greatest in younger (5.44%) versus middle (0.12%) and older-age (0.09%) at T3 (p = 0.005). For VST, mean supine %PCAv increase was greatest at T2 and T3 in middle (10.99%/10.12%) and older-age (17.36%/17.26%) versus younger (9.44%/8.89%) (p = 0.004/p = 0.002). We identified significant age-related NVC effects with VST-induced hyperactivation. This may reflect age-related compensatory processes in supine. Further work is required, using complex stimuli while standing/walking, examining NVC, aging and falls.

Effects of single- and bilateral limb immersion on systemic and cerebral hemodynamic responses to the cold pressor test.

The cold pressor test (CPT) involves cold water immersion of either the upper or lower limb(s) and elicits increases in sympathetic nervous activity (SNA), heart rate (HR), and mean arterial pressure (MAP) via stimulation of pain and cutaneous thermoreceptors. Greater pain perception during the CPT is associated with greater increases in SNA and more robust physiological responses. Due to potential differential sensitivity to both painful and thermal stimuli between upper and lower limbs, as well as potential effects of total exposure area, it is unclear whether the choice of limb(s) in CPT protocol design differentially affects systemic and cerebral hemodynamic responses. Our objective was to assess systemic and cerebral hemodynamic and ventilatory responses to different CPT protocols of the hand (CPTH), foot (CPTF), or bilateral feet (CPTBF). We hypothesized CPTBF would elicit greatest physiological responses due to increased exposure area to the cold stimulus. Twenty-eight (14 M, 14 F) healthy young adults [23.4 (SD: 2.4) yr] participated in three 3-min CPT protocols during a single visit. Blood pressure, HR, middle cerebral artery blood velocity (MCAv) and cerebrovascular conductance index, and end-tidal carbon dioxide ([Formula: see text]) were averaged over the final 30 s of each minute of the CPT for each protocol, and perceived pain was recorded at the end of each minute of the CPT. We found significant effects of the time-CPT protocol interaction on systolic blood pressure (P = 0.02), diastolic blood pressure (P < 0.01), MAP (P < 0.01), and HR (P < 0.001). There were no differences between CPT protocols on either MCAv (P = 0.4) or cerebrovascular conductance index (P = 0.1). HR responses peaked in the first minute of the CPT, and changes from baseline were greater in CPTBF [Δ14(16) beats/min] compared with CPTH [Δ5(13) beats/min; P = 0.01] and CPTF [Δ4.04(13.3) beats/min; P = 0.02]. MAP responses peaked in minute 2 of the CPT, and changes from baseline were greater in CPTH [Δ12(8) mmHg) and CPTBF (Δ13(9) mmHg] compared with CPTF [Δ8(7) mmHg; P < 0.01]. Perceived pain was significantly greater in the CPTBF [CPT1 7(2.3), CPT2 6.5(2.3), CPT3 6(3)] condition compared with CPTH [CPT1 6(1.3), CPT2 6(2.3), CPT3 6(2.3)] and CPTF [CPT1 6(3.0), CPT2 6(2.0), CPT3 5.5(3.0)] protocols at all three stages of the CPT (P ≤ 0.01). Our findings suggest choice of limb(s) in CPT protocols may lead to differences in systemic hemodynamic responses, with pain perception potentially influencing these responses. Based on our results, we suggest that choice of limb should be considered in future design of CPT studies, with hand CPT providing the best balance between participant tolerability and robust physiological responses.NEW & NOTEWORTHY Choice of limb(s) in cold pressor test (CPT) studies appears to influence systemic hemodynamics. Hand and bilateral feet induce more robust responses than single-foot CPT, potentially due to increased exposure area and pain perception. Despite no significant cerebrovascular effects, a sustained hyperventilatory response was noted in bilateral feet CPT. Hand CPTs may provide a balance between robust physiological responses and tolerability. These findings underscore the need for careful limb selection in future CPT studies.

Patients with amnestic mild cognitive impairment have higher cerebrovascular impedance than cognitively normal older adults.

Brain hypoperfusion is associated with cognitive impairment. Higher cerebrovascular impedance modulus (Z) may contribute to brain hypoperfusion. We tested hypotheses that patients with amnestic mild cognitive impairment (aMCI) (i.e., those who have a high risk of developing Alzheimer's disease) have higher Z than age-matched cognitively normal individuals, and that high Z is correlated with brain hypoperfusion. Fifty-eight patients with aMCI (67 ± 7 yr) and 25 cognitively normal subjects (CN, 65 ± 6 yr) underwent simultaneous measurements of carotid artery pressure (CAP, via applanation tonometry) and middle cerebral arterial blood velocity (CBV, via transcranial Doppler). Z was quantified using cross-spectral and transfer function analyses between dynamic changes in CBV and CAP. Patients with aMCI exhibited higher Z than NC (1.18 ± 0.34 vs. 1.01 ± 0.35 mmHg/cm/s, P = 0.044) in the frequency range from 0.78 to 4.29 Hz. The averaged Z in the frequency range (0.78-3.13 Hz) of high coherence (>0.9) was inversely correlated with total cerebral blood flow measured with 2-D Doppler ultrasonography normalized by the brain tissue mass (via structural MRI) across both patients with aMCI and NC (r = -0.311, P = 0.007), and in patients with aMCI alone (r = -0.306, P = 0.007). Our findings suggest that patients with aMCI have higher cerebrovascular impedance than cognitively normal older adults and that increased cerebrovascular impedance is associated with brain hypoperfusion.NEW & NOTEWORTHY This is the first study to compare cerebrovascular impedance between patients with amnestic mild cognitive impairment (aMCI) and age-matched cognitively normal individuals. Patients with aMCI had higher cerebrovascular impedance modulus than age-matched cognitively normal individuals, which was correlated with brain hypoperfusion. These results suggest the presence of cerebrovascular dysfunction in the dynamic regulation of cerebral blood flow in older adults who have high risks of Alzheimer's disease.

Cardiopulmonary Bypass Blood Flow Rates and Major Adverse Kidney Events in Cardiac Surgery: A Propensity Score-adjusted Before-After Study.

OBJECTIVES: Cardiac surgery associated-acute kidney injury is a common and serious postoperative complication of cardiac surgery, which is associated with increased postoperative morbidity and mortality. This study aimed to explore the association between cardiopulmonary bypass (CPB) blood flow rate (BFR), and major adverse kidney events (MAKEs) at day 30. DESIGN: Retrospective single-center before-after observational study. Patients were divided in 2 groups according to CPB flow rates: a first group with an institutional protocol targeting a CPB-BFR of >2.2 L/min/m² (low CPB-BFR group), and a second group with a modified institutional protocol targeting a CPB-BFR of >2.4 L/min/m² (high CPB-BFR group). The primary outcome was MAKE at 30 days, defined as the composite of death, renal replacement therapy or persistent renal dysfunction. SETTING: The data were collected from clinical routines in university hospital. PARTICIPANTS: Adult patients who underwent elective and urgent cardiac surgery without severe chronic renal failure, for whom CPB duration was ≥90 minutes. INTERVENTIONS: We included 533 patients (low CPB-BFR group, n = 270; high CPB-BFR group, n = 263). MEASUREMENTS AND MAIN RESULTS: A significant decrease in MAKE at 30 days was observed in the high CPB-BFR group (3% v 8%; odds ratio [OR], 0.779; 95% confidence interval [CI], 0.661-0.919; p < 0.001) mainly mediated by a lower 30-day mortality in the high CPB-BFR group (1% v 5%; OR, 0.697; 95% CI, 0.595-0.817; p = 0.001), as was renal replacement therapy (1% v 4%; OR, 0.739; 95% CI, 0.604-0.904; p = 0.016). CONCLUSIONS: In patients undergoing cardiac surgery, increased CPB-BFR was associated with a decrease in MAKE at 30 days including mortality and renal replacement therapy.

The prognostic value of changes in pulmonary vein flow patterns after surgical repair for primary mitral regurgitation.

BACKGROUND: The pulmonary vein (PV) flow pattern is influenced by the presence of mitral regurgitation (MR). After a successful reduction in MR severity, the pattern is expected to be changed. We aimed to evaluate the prognostic value of a change in the PV flow pattern in patients with primary MR undergoing mitral valve repair (MVR). METHODS: The PV flow pattern was assessed with transthoracic echocardiography in 216 patients (age 65 [IQR 56-72] years, 70% male) with primary MR before and after surgical MVR. The population was divided according to a change in the PV flow pattern following MVR into 'improvers' and 'non-improvers'. RESULTS: Non-improvers (15%) had a higher prevalence of paroxysmal AF at baseline (46% vs. 22%, p = 0.004), left ventricular dysfunction (LVEF ≤60%) (39% vs. 21%, p = 0.020), and had lower systolic pulmonary artery pressure (28[IQR 25-38] vs. 35[IQR 26-48] mmHg, p = 0.018) compared to improvers (85%). After a median follow-up of 83[IQR 43-140] months, 26(12%) patients died. Non-improvers had higher mortality rates than improvers (p = 0.009). On multivariable Cox regression analysis, a lack of improvement in the PV flow pattern remained independently associated with all-cause mortality (HR 2.322, 95% CI 1.140 to 4.729, P = 0.020). CONCLUSION: A lack of improvement in the PV flow pattern is independently associated with worse long-term survival in patients with primary MR undergoing MVR.

Techniques for imaging the choroid and choroidal blood flow in vivo.

The choroid, which is a highly vascularized layer between the retina and sclera, is essential for supplying oxygen and nutrients to the outer retina. Choroidal vascular dysfunction has been implicated in numerous ocular diseases, including age-related macular degeneration, central serous chorioretinopathy, polypoidal choroidal vasculopathy, and myopia. Traditionally, the in vivo assessment of choroidal blood flow relies on techniques such as laser Doppler flowmetry, laser speckle flowgraphy, pneumotonometry, laser interferometry, and ultrasonic color Doppler imaging. While the aforementioned methods have provided valuable insights into choroidal blood flow regulation, their clinical applications have been limited. Recent advancements in optical coherence tomography and optical coherence tomography angiography have expanded our understanding of the choroid, allowing detailed visualization of the larger choroidal vessels and choriocapillaris, respectively. This review provides an overview of the available techniques that can investigate the choroid and its blood flow in vivo. Future research should combine these techniques to comprehensively image the entire choroidal microcirculation and develop robust methods to quantify choroidal blood flow. The potential findings will provide a better picture of choroidal hemodynamics and its effect on ocular health and disease.

Dynamic cerebral autoregulation during repeated handgrip exercise: comparisons with spontaneous rest and sit-stand maneuvers.

Induced arterial pressure oscillation may improve the assessment of dynamic cerebral autoregulation (dCA) with transfer function analysis (TFA). This study investigated dCA during repeated handgrip exercise (RHE) compared with spontaneous rest and sit-stand maneuvers (SSM), often used in cerebrovascular research. After a 5-min rest, 20 healthy young adults (10 women and 10 men) underwent 5 min of RHE (30% maximal voluntary contraction) and SSM at 0.05 Hz and 0.10 Hz each in random order. Power spectral density (PSD) and TFA gain, phase, coherence of mean arterial pressure (MAP), and blood velocity in the middle cerebral artery (MCAvmean) were measured in very low (VLF: 0.02-0.07 Hz) and low (LF: 0.07-0.20 Hz) frequencies. End-tidal CO2 (EtCO2) was continuously recorded throughout data collection. Compared with rest, RHE increased the PSD of MAP and MCAvmean in VLF (444% and 273%, respectively) and LF (1,571% and 1,765%, respectively) (all P < 0.001). Coherence increased during RHE (VLF: 131%, LF: 128%) and SSM (VLF: 166%, LF: 136%) compared with rest (all P < 0.05). TFA gain and phase were similar between RHE and rest, but VLF gain was higher, whereas VLF and LF phases were lower during SSM than RHE (all P < 0.05). EtCO2 was higher during SSM than rest and RHE (both P < 0.05), with the individual EtCO2 changes positively correlated with VLF gain (r = 0.538, P < 0.001). These results indicate that RHE significantly increases arterial pressure oscillation and TFA coherence and may improve dCA assessment in individuals unable to perform repeated postural changes.NEW & NOTEWORTHY This is the first study investigating dynamic cerebral autoregulation (dCA) during light-intensity repeated handgrip exercise (RHE) compared with rest and sit-stand maneuvers (SSM) using transfer function analysis (TFA). Compared with rest, RHE significantly increased oscillations of arterial blood pressure and cerebral blood velocity and coherence, whereas SSM exhibited the highest oscillations and coherence. These findings suggest that RHE may serve as an alternative method for assessing dCA in individuals unable to perform repeated postural changes.

Analysis of phase shift between pulse oscillations of macro- and microvascular cerebral blood flow in patients with traumatic brain injury.

PURPOSE: After a traumatic brain injury (TBI), monitoring of both macrovascular and microvascular blood circulation can potentially yield a better understanding of pathophysiology of potential secondary brain lesions. We investigated the changes in phase shift (PS) between cardiac-induced oscillations of cerebral blood flow (CBF) measured at macro (ultrasound Doppler) and microvascular (laser Doppler) level. Further we assessed the impact of intracranial pressure (ICP) on PS in TBI patients. A secondary aim was to compare PS to TCD-derived cerebral arterial time constant (τ), a parameter that reflects the circulatory transit time. METHODS: TCD blood flow velocities (FV) in the middle cerebral artery, laser Doppler blood microcirculation flux (LDF), arterial blood pressure (ABP), and ICP were monitored in 29 consecutive patients with TBI. Eight patients were excluded because of poor-quality signals. For the remaining 21 patients (median age = 23 (Q1: 20-Q3: 33); men:16,) data were retrospectively analysed. PS between the fundamental harmonics of FV and LDF signals was determined using spectral analysis. τ was estimated as a product of cerebrovascular resistance and compliance, based on the mathematical transformation of FV and ABP, ICP pulse waveforms. RESULTS: PS was negative (median: -26 (Q1: -38-Q3: -15) degrees) indicating that pulse LDF at a heart rate frequency lagged behind TCD pulse. With rising mean ICP, PS became more negative (R = -0.51, p < 0.019) indicating that delay of LDF pulse increases. There was a significant correlation between PS and cerebrovascular time constant (R = -0.47, p = 0.03). CONCLUSIONS: Pulse divergence between FV and LDF became greater with elevated ICP, likely reflecting prolonged circulatory travel time.

Reconstructing blood flow in data-poor regimes: a vasculature network kernel for Gaussian process regression.

Blood flow reconstruction in the vasculature is important for many clinical applications. However, in clinical settings, the available data are often quite limited. For instance, transcranial Doppler ultrasound is a non-invasive clinical tool that is commonly used in clinical settings to measure blood velocity waveforms at several locations. This amount of data is grossly insufficient for training machine learning surrogate models, such as deep neural networks or Gaussian process regression. In this work, we propose a Gaussian process regression approach based on empirical kernels constructed by data generated from physics-based simulations-enabling near-real-time reconstruction of blood flow in data-poor regimes. We introduce a novel methodology to reconstruct the kernel within the vascular network. The proposed kernel encodes both spatiotemporal and vessel-to-vessel correlations, thus enabling blood flow reconstruction in vessels that lack direct measurements. We demonstrate that any prediction made with the proposed kernel satisfies the conservation of mass principle. The kernel is constructed by running stochastic one-dimensional blood flow simulations, where the stochasticity captures the epistemic uncertainties, such as lack of knowledge about boundary conditions and uncertainties in vasculature geometries. We demonstrate the performance of the model on three test cases, namely, a simple Y-shaped bifurcation, abdominal aorta and the circle of Willis in the brain.

Clinical relevance of aortic conduit and reservoir function.

BACKGROUND: Aortic conduit and reservoir functions can be directly measured by four-dimensional flow (4D flow) cardiovascular magnetic resonance (CMR). METHODS: Twenty healthy controls (10 young and 10 age-gender-matched old controls) and 20 patients with heart failure with preserved ejection fraction (HFpEF) were recruited. All had 4D flow CMR. Flow was quantified at the ascending and descending aorta levels. In addition, at the ascending aorta level, we quantified systolic flow displacement (FDs) and systolic flow reversal ratio (sFRR). The aortic conduit function was defined as the relative drop in systolic flow from the ascending to the descending aorta (∆Fs). Aortic reservoir function was defined as descending aortic diastolic stroke volume (DAo SVd). RESULTS: Both ∆Fs (R=0.51, p=0.001) and DAo SVd (R=-0.68, p=0.001) were significantly associated with ageing. Native T1 (R=0.51, p=0.001) and extracellular volume (R=0.51, p=0.001) showed maximum association with ∆Fs. ∆Fs significantly increased in HFpEF versus age-gender-matched controls (41±8% vs 52±12%, p=0.02). In multiple regression, only ∆Fs and DAo SVd were independent predictors of the estimated glomerular filtration rate (model R=0.77, p=0.0001). FDs was significantly associated with ∆Fs (R=0.4, p=0.01) and DAo SVd (R=-0.48, p=0.002), whereas sFRR was mainly associated with DAo SVd (R=-0.46, p=0.003). CONCLUSION: Both aortic conduit and reservoir function decline with age and this decline in aortic function is also independently associated with renal functional decline. Ascending aortic turbulent flow signatures are associated with loss of aortic conduit and reservoir functions. Finally, in HFpEF, aortic conduit and reservoir function demonstrate progressive decline. TRIALS REGISTRATION NUMBER: NCT05114785.

Effects of different VV ECMO blood flow rates on lung perfusion assessment by hypertonic saline bolus-based electrical impedance tomography.

OBJECTIVE: Our study aimed to investigate the effects of different extracorporeal membrane oxygenation (ECMO) blood flow rates on lung perfusion assessment using the saline bolus-based electrical impedance tomography (EIT) technique in patients on veno-venous (VV) ECMO. METHODS: In this single-centered prospective physiological study, patients on VV ECMO who met the ECMO weaning criteria were assessed for lung perfusion using saline bolus-based EIT at various ECMO blood flow rates (gradually decreased from 4.5 L/min to 3.5 L/min, 2.5 L/min, 1.5 L/min, and finally to 0 L/min). Lung perfusion distribution, dead space, shunt, ventilation/perfusion matching, and recirculation fraction at different flow rates were compared. RESULTS: Fifteen patients were included. As the ECMO blood flow rate decreased from 4.5 L/min to 0 L/min, the recirculation fraction decreased significantly. The main EIT-based findings were as follows. (1) Median lung perfusion significantly increased in region-of-interest (ROI) 2 and the ventral region [38.21 (34.93-42.16)% to 41.29 (35.32-43.75)%, p = 0.003, and 48.86 (45.53-58.96)% to 54.12 (45.07-61.16)%, p = 0.037, respectively], whereas it significantly decreased in ROI 4 and the dorsal region [7.87 (5.42-9.78)% to 6.08 (5.27-9.34)%, p = 0.049, and 51.14 (41.04-54.47)% to 45.88 (38.84-54.93)%, p = 0.037, respectively]. (2) Dead space significantly decreased, and ventilation/perfusion matching significantly increased in both the ventral and global regions. (3) No significant variations were observed in regional and global shunt. CONCLUSIONS: During VV ECMO, the ECMO blood flow rate, closely linked to recirculation fraction, could affect the accuracy of lung perfusion assessment using hypertonic saline bolus-based EIT.

Effects of smoking cessation on endothelial function as assessed by flow-mediated total dilation.

BACKGROUND: In assessing the effects of smoking cessation on endothelial function, low-flow-mediated constriction (L-FMC) may provide complementary information to flow-mediated dilation (FMD). However, the value of flow-mediated total dilation (FMTD), an index that incorporates L-FMC into FMD, remains underreported. We aimed to evaluate the effect of smoking cessation on endothelial function, as assessed by FMD and FMTD, and clarify its associated clinical factors. METHODS: We enrolled 118 consecutive current smokers without previous coronary artery disease (72.9% were men; age: 59 ± 11 years) who underwent smoking cessation treatment. The clinical variables %FMD, %L-FMC, and %FMTD were examined before and 20 weeks after treatment initiation. A multivariate linear regression model was used to investigate the effects of smoking cessation on %FMD and %FMTD and the interaction between smoking cessation and baseline clinical variables. RESULTS: After 20 weeks, 85 smokers (69.4% were men; age: 59 ± 12 years) ceased smoking (abstainers), whereas 33 smokers (81.8% were men; age: 58 ± 11 years) did not (continued smokers). The estimated group differences (abstainers - continued smokers) in changes in the %FMD and %FMTD were 0.77% (95% confidence interval [CI], -0.22-1.77%; p = 0.129) and 1.17% (95% CI, 0.16-2.18%; p = 0.024), respectively. Smoking cessation-associated improvement in %FMTD was greater in women than in men (5.41% [95% CI, 3.15-7.67%] versus 0.24% [95% CI, -0.81-1.28%]; p-value for interaction, < 0.001). Additionally, a greater %FMTD improvement was observed in patients who smoked fewer cigarettes per day (p-value for interaction, 0.042) and those who had a smaller resting baseline lumen diameter (Dbase) (p-value for interaction, 0.023). CONCLUSIONS: Smoking cessation was associated with an improvement in %FMTD. Sex, cigarettes smoked per day, and Dbase significantly affected this improvement. The FMTD may help in risk stratification after smoking cessation.

The effect of flow-derived mechanical cues on the growth and morphology of platelet aggregates under low, medium, and high shear rates.

Platelet aggregation is a dynamic process that can obstruct blood flow, leading to cardiovascular diseases. While many studies have demonstrated clear connections between shear rate and platelet aggregation, the impact of flow-derived mechanical signals on this process is not fully understood. The objective of this work is to investigate the role of flow conditions on platelet aggregation dynamics, including effects on growth, shape, density composition, and their potential correlation with binding processes that are characterised by longer (e.g., via αIIbß3 integrin) and shorter (e.g., via VWF) initial binding times. In vitro blood perfusion experiments were conducted at wall shear rates of 800, 1600 and 4000 s-1. Detailed analysis of two modalities of experimental images was performed to offer insights into the morphology of platelet aggregates. A consistent structural pattern was observed across all samples: a high-density core enveloped by a low-density outer shell. An image-based 3D computational blood flow model was subsequently employed to study the local flow conditions, including binding availability time and flow-derived mechanical signals via shear rate and rate of elongation. The results show substantial dependence of the aggregation dynamics on these flow parameters. We found that the different binding mechanisms that prefer different flow regimes do not have a monotonic cross-over in efficiency as the flow increases. There is a significant dip in the cumulative aggregation potential in-between the preferred regimes. The results suggest that treatments targeting the biomechanical pathways could benefit from creating conditions that exploit these low-efficiency zones of aggregation.

[4D flow MRI: value and clinical perspectives in patients with pathology of the heart and great vessels (part 2): A review].

The study of blood flow is becoming a new trend in cardiology and cardiovascular surgery. Based on the literature and our own data, a review is presented on the use of 4D flow in diseases of the heart and blood vessels. The main state of the question about the features of the application of the technique in various pathologies of the cardiovascular system is described in detail, the priorities, limitations and promising directions of the technique application are considered taking into account the goals of practical medicine. The review consists of two parts. The first is devoted to general issues, limitations of the technique, and issues of 4D flow mapping in patients with lesions of the great vessels. In the second part, the emphasis is on the use of 4D flow MRI in the study of intraventricular blood flow and the application of the technique in congenital heart and vascular diseases.