In this series of three cases, we describe the vascular steal phenomenon in an otherwise normal lower limb secondary to hyperemia in the contralateral lower limb. In each of the cases, post-inflammatory hyperemia in the involved lower limb was associated with a significant reduction in blood flow in the contralateral normal lower limb. We attempt to explain the imaging findings in these three cases using the equation of continuity in fluid dynamics. To the best of our knowledge, a description of such kind is unavailable in the published literature.

A data-driven reduced order model (ROM) based on a proper orthogonal decomposition-radial basis function (POD-RBF) approach is adopted in this paper for the analysis of blood flow dynamics in a patient-specific case of atrial fibrillation (AF). The full order model (FOM) is represented by incompressible Navier-Stokes equations, discretized with a finite volume (FV) approach. Both the Newtonian and the Casson\'s constitutive laws are employed. The aim is to build a computational tool able to efficiently and accurately reconstruct the patterns of relevant hemodynamics indices related to the stasis of the blood in a physical parametrization framework including the cardiac output in the Newtonian case and also the plasma viscosity and the hematocrit in the non-Newtonian one. Many FOM-ROM comparisons are shown to analyze the performance of our approach as regards errors and computational speed-up.

OBJECTIVE: Tortuosity of the internal carotid artery (ICA) is associated with intracranial aneurysms (IAs). The siphon is the most curved segment of the ICA, but its morphology has controversial effects on IAs. This study aimed to explore the morphometric features of the siphon and the potential hemodynamic mechanisms that may affect C7 aneurysm formation.
METHODS: In this study 32 patients with C7 aneurysms diagnosed at Xiangya Hospital between 2019 and 2021 and 32 control subjects were enrolled after propensity score matching. Computed tomography angiography (CTA) images were acquired to measure morphologic features, and then, by combining clinical data, simplified carotid siphon models were constructed, and computational fluid dynamics (CFD) analysis was performed.
RESULTS: The presence of C7 aneurysms was associated with the height of the C4-C6 curved arteries (odds ratio [OR] 0.028, 95% confidence interval [CI] 0.003-0.201; P < 0.001). The heights of the C4-C6 curved arteries in the aneurysm group were significantly shorter than those in the control group. The CFD analysis revealed that shorter C4-C6 bends led to greater blood velocity and pressure in the C7 segment arteries.
CONCLUSIONS: A shorter C4-C6 bend was associated with distal C7 aneurysm formation, and an elaborate hemodynamic mechanism may underlie this association.

BACKGROUND: Effective management of complications in sickle cell disease (SCD), such as stroke prevention, often necessitates the use of blood transfusions. However, individuals who adhere to the religious tenets of Jehovah\'s Witnesses strictly abstain from accepting blood transfusions, thereby presenting a formidable challenge in clinical decision-making.
METHODS: This is a case of a 3 year old child Jehovah\'s Witness who was found to have significantly elevated transcranial Doppler (TCD) velocity values between 193 and 203 cm/s, following routine screening. This was an otherwise clinically stable child, whose mother was diligently ensuring he had adequate medical care. Ideally, a prophylactic exchange blood transfusion program would have been commenced immediately but was not done due to due to the lack of consent from the caregiver. Patient was initially on hydroxyurea at 15 mg/kg and self medicating on omega 3 supplements and astymin syrup. Further elevation of TCD velocity upto 242 cm/s after a repeat testing, necessitated graduated increase of the dosage of hydroxyurea to 35 mg/kg to optimize its therapeutic effect, and discontinuation of omega 3 fatty acids and replacement of astymin with folic acid, vitamin C and B complex. Following these adjustments, the TCD dropped to below 190 cm/s reducing the risk of stroke in the child.
CONCLUSIONS: This case report demonstrates the successful implementation of a bloodless management strategy for stroke prevention in a Jehovah\'s Witness child with SCD. This study contributes to the existing literature by providing valuable insights and practical guidance for healthcare providers facing similar ethical and medical dilemmas.

METHODS: Herein we present the case of a 33-year nulliparous woman at 21 weeks of gestation with mitral valve vegetation resulting from infective endocarditis. Due to the mother\'s critical condition caused by consecutive thromboembolic events, surgery with cardiopulmonary bypass was indicated. During surgery the fetus was monitored by a specialized obstetrician who repetitively measured the Doppler indices of the umbilical artery, Ductus venosus and uterine artery. Right after CO2 was insufflated into the operating area, the Doppler monitoring showed an increased Pulsatility Index of the Umbilical artery right before fetal distress with bradycardia occurred. A subsequent maternal arterial blood gas analysis showed an acidosis with hypercapnia. Consequently, the CO2 insufflation was stopped and the gas flow on the Heart Lung Machine increased. After regaining homeostasis of acidosis, the Doppler Indices and fetal heart rate recovered. The remaining surgery and postoperative course were uneventful. At the 37 weeks of gestation a healthy boy was delivered by Cesarean section and at the age of two years, the neurodevelopment was assessed, which indicated normal development in mental cognition, language and motoric. This report presents a periodic Doppler examination of the maternal and fetal circulation during surgery on CPB while also discussing the possible impact of fetal monitoring in managing open cardiac surgery in pregnancy.

Cannabis consumption during pregnancy increases the risk of pregnancy and neonatal complications. Since the underlying mechanism is unknown, the purpose of this study is to evaluate the changes in maternal and fetal blood flow in pregnancies exposed to cannabis, Δ9-tetrahydrocannabinol (THC).
A case-control study between 2013 and 2020, included women with continued cannabis exposure during the pregnancies, defined by qualitative detection of THC in urine (Cannabis Group), and low-risk pregnancy women divided into tobacco smokers (Tobacco Group), and non-tobacco smokers (Control Group). We evaluated the association between cannabis consumption and maternal and fetal blood flow parameters measured by Doppler ultrasound: uterine artery at 11-14, 20-22 and 33-35 weeks, umbilical artery and middle cerebral artery at 33-35 weeks. Cerebral-placental ratio was calculated.
Overall, 275 participants were included, 60 in the Cannabis Group, 17 in the Tobacco Group and 198 in the Control Group. At 33-35 weeks, differences were found in the umbilical artery pulsatility index (PI) (1.05 ± 0.23, 1.06 ± 0.19, 0.93 ± 0.15, P < 0.01), middle cerebral artery PI (1.75 ± 0.35, 1.90 ± 0.45, 1.88 ± 0.34, P < 0.05), cerebral-placental ratio (1.69 ± 0.40, 1.85 ± 0.53, 2.07 ± 0.47, P < 0.05) and mean uterine artery PI (0.89 ± 0.26, 0.73 ± 0.19, 0.74 ± 0.20, P < 0.01), respectively. On logistic regression analysis, adjusted for maternal age, maternal body mass index, maternal weight and white ethnicity, both cannabis and tobacco were predictors for increased umbilical artery PI, but only cannabis was a predictor for a decreased cerebral-placental ratio and an increased uterine artery PI at 33-35 weeks.
Data from a large cohort of continuous cannabis exposure pregnancies show that cannabis is associated with maternal and fetal blood flow changes. However, it is not possible to disentangle the association of the tobacco and cannabis.

OBJECTIVE: To quantify the hemodynamic and thrombotic effect of COVID-19 on the eye microcirculation of patients with thromboprophylaxis, shortly after hospital discharge.
METHODS: This case-control study included 17 COVID-19 survivors (named \"COVID-19 Group\") and 17 healthy volunteers (named \"Control Group\"). Axial blood velocity (Vax) and percentage of occluded vessels (POV) were quantified by Conjunctival Video Capillaroscopy (CVC). Microvessels were identified and classified as \"capillaries\" (CAP), \"postcapillary venules of size 1\" (PC1), and \"postcapillary venules of size 2\" (PC2).
RESULTS: The COVID-19 Group did not differ significantly in basic demographics from the Control Group. In the COVID-19 Group, there was a statistically significant (p < 0.001) reduction of Vax (39%, 49% and 47%, for CAP, PC1, and PC2, respectively) in comparison to the Control Group and a sizeable (p < 0.001) increase of POV (600%) in comparison to the Control Group.
CONCLUSIONS: COVID-19 not only reduces significantly axial blood velocity in the capillaries and postcapillary venules of the eye but has also a devastating effect on microthrombosis (POV) despite thromboprophylaxis treatment. This gives a possible explanation for long COVID and a hint about the existence of a possibly unknown coagulation factor.

A 25-year-old women was admitted to the department of Neurology in Affiliated 2nd Hospital of Hainan Medical University due to recurrent syncope for 8 years and return for 2 months. She had multiple episodes of syncope at onset. She presented with the feeling of weakness in both lower limbs, and fatigue in the past year. She experienced pain in the waist and limbs joint in recent three months. Physical examination showed joint hyperactivity in metacarpophalangeal joints of both upper limbs, increased skin elasticity. Active-standing transcranial Doppler (TCD) test showed that the average heart rate (HR) and the average middle cerebral artery (MCA) blood flow velocity in the supine position were 79 beats/min and 62 cm/s, respectively; while the average HR and the average MCA blood flow velocity in the standing position were 126 beats/min, 47 cm/s. Meanwhile,the blood pressure was normal during the test of supine-to-standing TCD. Genetic testing indicated LDB3 transgenation. The patient was diagnosed as postural tachycardia syndrome (joint-hypermobility-related), Ehlers-Danlos syndrome, and relieved by fluid infusion and rehabilitation therapy.
患者女，25岁，因反复晕厥8年，再发2个月就诊于海南医学院第二附属医院神经内科。患者以反复晕厥起病，近1年感双下肢乏力、易疲劳，近3个月感腰部及四肢关节疼痛，双上肢掌指关节活动度增大，皮肤弹性增加。卧立位经颅多普勒超声（TCD）示卧位平均心率79 次/min；立位平均心率126 次/min；卧立位血压正常；大脑中动脉卧位平均脑血流速度62 cm/s；立位平均脑血流速度47 cm/s。基因检测提示LDB3基因突变。最终诊断：体位性心动过速综合征（关节过度活动型），Ehlers-Danlos综合征，予以补液、康复治疗后好转。.

Rotator cuff tears are commonly associated with pain at rest and at night particularly if lying on the affected shoulder. This case describes a 54-year-old man who reported concerns of severe night pain in his left shoulder and had to undergo arthroscopic rotator cuff repair. The severity of night pain and blood flow velocity in the anterior humeral circumflex artery (AHCA) were measured over time. The patient reported his night pain as 10/10 on the numerical rating scale in the first week after surgery. In the fourth week, he rated his night pain as 6/10, and in the fifth week, his pain was <2/10. We measured blood flow velocity in the AHCA using a 3-11MHz color Doppler and power Doppler ultrasound (SONIMAGE HS2, Konica Minolta, Tokyo, Japan), and we calculated peak systolic velocity. The course of peak systolic velocity in the AHCA ranged from 27.7 to 62.4 cm/s until four weeks after surgery when his night pain was severe; AHCA flow velocity ranged from 16.7 to 19.3 cm/s five weeks after surgery when his night pain had reduced. The initially high blood flow velocity in the AHCA decreased almost simultaneously with the improvement in night pain. Our case highlights that blood flow velocity in the AHCA synchronized with the severity of night pain, which may contribute to the understanding of sleep disturbances in patients after arthroscopic rotator cuff repair.

BACKGROUND: Doppler transthoracic echocardiography is routinely performed to measure peak mitral inflow velocities in the assessment of left ventricular diastolic function. The limitations of echocardiography are well documented, but its accuracy in the measurement of transmitral peak velocity in the presence of aortic valve regurgitation has not yet been compared with four-dimensional flow cardiac magnetic resonance imaging. Four-dimensional flow cardiac magnetic resonance imaging offers time-resolved cross-sectional velocity information that can be used to investigate mitral inflow peak velocity. We present a case report demonstrating the potential superior capabilities of four-dimensional flow cardiac magnetic resonance imaging in accurately detecting mitral inflow velocities over Doppler echocardiography in patients with aortic regurgitation.
METHODS: A 67-year-old Caucasian female presented to our outpatient cardiology clinic with exertional dyspnea. Doppler transthoracic echocardiography identified moderate to severe aortic regurgitation. Mapping of mitral inflow peak velocities proved challenging with Doppler echocardiography. Additionally, four-dimensional flow cardiac magnetic resonance imaging with automated three-dimensional flow streamlines was performed, which allowed for more accurate detection of mitral inflow peak velocities.
CONCLUSIONS: Doppler echocardiography has a limited role in mitral inflow assessment where aortic regurgitation is present. In such cases, four-dimensional flow cardiac magnetic resonance imaging is an alternative imaging technique that may circumvent this issue and allow mitral inflow assessment.