Influence of blood Po2 on the stability of agitated saline contrast.

The utility of transthoracic saline contrast echocardiography (TTSCE) to assess blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) in humans is limited due to the potential destabilizing effects of the gas concentration gradients established in varied blood-gas environments. This study assessed the specific effect of a hyperoxic and mixed venous blood-gas environment on the stability of saline contrast. We hypothesized that the rate of contrast mass lost in hyperoxic blood would be similar to mixed venous due to the establishment of equal and opposing gas gradients (O2, N2, CO2) created when the partial pressure of dissolved gases is manipulated. Using an in vitro model of the pulmonary circulation perfused with defibrinated sheep blood and a membrane oxygenator to control blood gases, we assessed the percent contrast conserved (an index of contrast stability) between inflow and outflow sites at multiple flow rates (1.8, 2.8, 4.3, and 6.8 L/min) in a hyperoxic (Po2: 646 ± 16 mmHg; Pco2: 0 ± 0 mmHg) and a mixed venous blood gas condition (Po2: 35 ± 3 mmHg; Pco2: 40 ± 0 mmHg). We found significant contrast decay with time in both conditions, with slightly higher contrast conservation in the hyperoxia trials (64 ± 32%) versus the mixed venous trials (55 ± 21%). These findings suggest that contrast stability is not likely a factor affecting the interpretation of TTSCE performed in healthy humans breathing hyperoxia and lends support to the existence of a local O2-dependent mechanism contributing to the regulation of Q̇IPAVA.NEW & NOTEWORTHY Hyperoxic blood has a small stabilizing effect on agitated saline contrast compared with mixed venous blood, lending support to studies that show the reversal of exercise-induced blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) with hyperoxia. These data support the possible presence of a local O2-dependent regulatory mechanism within the pulmonary vasculature that may play a role in Q̇IPAVA regulation.

Non-invasive dynamic observation of placental vascular anastomoses in monochorionic twins: Assessment using three-dimensional sonography combined with tomographic ultrasound imaging.

INTRODUCTION: Three-dimensional (3D) sonography combined with tomographic ultrasound imaging (TUI) to observe placental vascular anastomoses in monochorionic diamniotic (MCDA) twin pregnancies was evaluated. METHODS: Women with MCDA twin pregnancies at a gestational age of 16-32 weeks were enrolled in this retrospective study. Placental anastomoses were detected using two-dimensional (2D) and 3D sonography. Two-dimensional data were obtained by color and spectral Doppler and 3D data with high-definition flow within the area between twins' umbilical cord insertions. Volume post-processing using TUI mode identified anastomoses. Anastomotic findings on ultrasound were compared with fetoscopic surgery or postnatally injected placentas for diagnostic value. Anastomoses detection was compared between the two imaging modalities. RESULTS: Seventy-six twin pregnancies were analyzed: 11 selective intrauterine growth restrictions (sIUGR), 10 twin-to-twin transfusion syndrome (TTTS), and 55 without complications. Seventy-one twin pregnancies had arterio-arterial (AA) anastomoses and 75 had arterio-venous (AV) anastomoses. Three-dimensional sonography combined with TUI was more sensitive (87.3%) and accurate (88.2%) in detecting AA anastomoses than 2D sonography (74.6%, 76.3%, respectively; P < 0.05), but had comparable sensitivity for AV anastomoses. The specificity of both modalities for anastomoses was 100%. The detection rate of AA anastomoses by 3D modality was (40%) TTTS vs. (87.3%) normal (P < 0.05), but comparable (90.9%) for sIUGR. The detection rates of AV anastomoses (90%, 81.8%) in TTTS and sIUGR were comparable with (87.3%) normal (P > 0.05). DISCUSSION: Three-dimensional sonography combined with TUI highlighted placental anastomoses and may be useful for the clinical diagnosis and therapy of MCDA twin complications.

The assessment of placental sharing using X-ray angiogram versus digital photograph: A prospective study.

INTRODUCTION: We aim to compare two different methods for the assessment of placental sharing in monochorionic diamniotic twins: X-ray-angiogram and digital photograph of the placenta. METHOD: We included the placentas of a prospective series of twins that were followed from the first trimester onward and resulted in a double live birth or double stillbirth between April 2016 and February 2019. Injection was performed after delivery and an X-ray angiogram was made, as well as a digital photograph. On both of these, the territory of each twin was measured two investigators (IC and LL). Placental sharing discordance was determined using the following formula: (larger territory - smaller territory)/larger territory. We calculated the intra-class correlation coefficients for intra-observer and inter-observer reliability and used Bland-Altman analysis to compare both methods. RESULTS: 77 placentas were included in the analysis. For both methods, there was an excellent intra- and inter-observer reliability. The mean difference in sharing (bias) on the X-ray and digital photograph using Bland-Altman analysis was 3,7% (95% CI 1,1% - 6,3%), where the digital photograph tends to overestimate the discordance. Limits of agreement were between -19% and 26%. CONCLUSION: Delineation of the placental sharing on a digital photograph slightly overestimates the discordance. Since the venous territory on X-ray angiogram physically determines where each twin gets its oxygenated blood, X-ray angiogram may be a better method to determine placental sharing, although the digital photograph constitutes a valid alternative.

Spontaneous splenoazygos shunt in a patient with portal hypertension: an exceedingly rare occurrence

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The protective effect of persistent trigeminal artery in patients with ischemic stroke.

BACKGROUND: Almost all case reports related to persistent trigeminal artery indicated that the existence of persistent trigeminal artery may increase the risk of ischemic stroke. However our case demonstrated that the persistent trigeminal artery may also play a protective role in preventing severe ischemic stroke by functioning as collateral circulation. CASE PRESENTATION: We reported a patient with left internal carotid artery occlusion with persistent trigeminal artery manifesting only as a minor acute ischemia stroke exhibiting acute onset of dizziness and difficulty in walking. Brain MRI showed two small areas of restricted diffusion on diffusion-weighted imaging in the left hemisphere. The digital subtraction angiography showed his left middle cerebral artery and bilateral anterior cerebral artery were supplied by the basilar artery via a persistent trigeminal artery. Furthermore, CT perfusion showed no remarkable difference between the two hemispheres. CONCLUSIONS: Persistent trigeminal artery may have a protective role in the setting of an acquired occlusion of homolateral internal carotid artery. Therefore, it is important to fully assess the presence of the persistent trigeminal artery in acute ischemic stroke.

The roles of superficial anastomoses in twin-twin transfusion syndrome.

OBJECTIVE: We aimed to evaluate whether types of vascular anastomoses affect fetal demise (FD) in twin-twin transfusion syndrome (TTTS) after fetoscopic laser photocoagulation (FLP). METHODS: All TTTS patients who underwent FLP in our institution from 2005 to 2017 were included. We described vascular anastomoses during FLP as either arterio-arterial (AA), veno-venous (VV), or arterial-venous (AV), and abnormal fetal Doppler waveforms before FLP. We also analyzed risk factors for FD following FLP. RESULTS: In total, 184 TTTS placentas following FLP were analyzed (36 cases of donor-only FD, 12 cases of recipient-only FD, 3 cases of double FD, and 133 cases of both alive). AA anastomoses prevalence, absent or reverse end-diastolic velocity of umbilical artery (UAAREDV) of donor before FLP, gestational age at the time of FLP and operation time of FLP were independent risk factors for donor FD. VV anastomoses prevalence and UAAREDV of recipient before FLP were independent risk factors for recipient FD. VV anastomoses prevalence was higher in double FD cases than in FD of one twin or both alive (p = 0.002). AV anastomoses number and number of cases with more AV anastomoses from donor to recipient were not significantly different between FD and non-FD cases. DISCUSSION: AA anastomoses are associated FD of the donor following FLP and may protect the donor from hypovolemia before FLP. VV anastomoses are detected more frequently in FD of the recipient and double FD placentas following FLP and may rescue hypervolemia of the recipient or circulations of both fetuses before FLP.

A teenage patient with autosomal recessive polycystic kidney disease, a splenorenal shunt, and congenital hepatic fibrosis: a case report / Doença renal policística autossômica recessiva, shunt esplenorrenal e fibrose hepática congênita em adolescente: relato de caso

ABSTRACT A 16-year-old female patient previously diagnosed with autosomal recessive polycystic kidney disease (ARPKD) presented with acute bilateral pneumonia, upper gastrointestinal bleeding caused by ruptured esophageal varices, ascites, and lower limb edema. She required intensive care and an endoscopic procedure to treat the gastrointestinal bleeding. The analysis of the differential diagnosis for chronic liver disease indicated she had a spontaneous splenorenal shunt. Ultrasound-guided biopsy revealed the patient had cirrhosis, as characteristically seen in individuals with ARPKD. She had no symptoms at discharge and was referred for review for a combined transplant.

RESUMO Relato de caso de uma paciente adolescente de 16 anos de idade com diagnóstico prévio de doença renal policística autossômica recessiva (DRPAR), que apresentou quadro agudo de pneumonia bilateral e hemorragia digestiva alta por ruptura de varizes esofágicas, bem como ascite e edema de membros inferiores. Necessitou de estabilização clínica intensiva e tratamento endoscópico do sangramento digestivo. Após investigação dos diagnósticos diferenciais da hepatopatia crônica, diagnosticou-se shunt esplenorrenal espontâneo, e realizou-se biópsia hepática guiada por ecografia com diagnóstico de cirrose, espectro típico da DRPAR. Recebeu alta hospitalar assintomática e foi encaminhada para avaliação de transplante duplo.

High sensitivity and specificity of 4D-CTA in the detection of cranial arteriovenous shunts.

PURPOSE: In a prospective cohort study, we evaluated the diagnostic accuracy of time-resolved CT angiography (4D-CTA) compared to digital subtraction angiography (DSA) for detecting cranial arteriovenous shunts. MATERIAL AND METHODS: Patients were enrolled if a DSA had been ordered querying either a dural arteriovenous fistula (dAVF) or a cerebral arteriovenous malformation (bAVM). After enrolment, both a DSA and a 4D-CTA were performed. Both studies were evaluated using a standardized form. If a dAVF or bAVM was found, its classification, angioarchitectural details, and treatment options were recorded. RESULTS: Ninety-eight patients were enrolled and 76 full datasets were acquired. DSA demonstrated a shunting lesion in 28 out of 76 cases (prevalence 37%). 4D-CTA demonstrated all but two of these lesions (sensitivity of 93%) and produced one false positive (specificity of 98%). These numbers yielded a positive predictive value (PPV) of 96% and a negative predictive value (NPV) of 96%. Significant doubt regarding the 4D-CTA diagnosis was reported in 6.6% of all cases and both false-negative 4D-CTA results were characterized by such doubt. CONCLUSIONS: 4D-CTA has very high sensitivity and specificity for the detection of intracranial arteriovenous shunts. Based on these results, 4D-CTA may replace DSA imaging as a first modality in the diagnostic workup in a large number of patients suspected of a cranial dAVF or bAVM, especially if there is no doubt regarding the 4D-CTA diagnosis. KEY POINTS: • 4D-CTA was shown to have a high diagnostic accuracy and is an appropriate, less invasive replacement for DSA as a diagnostic tool for cranial arteriovenous shunts in the majority of suspected cases. • Doubt regarding the 4D-CTA result should prompt additional DSA imaging, as it is associated with false negatives. • False-positive 4D-CTA results are rare, but do exist.

A teenage patient with autosomal recessive polycystic kidney disease, a splenorenal shunt, and congenital hepatic fibrosis: a case report.

A 16-year-old female patient previously diagnosed with autosomal recessive polycystic kidney disease (ARPKD) presented with acute bilateral pneumonia, upper gastrointestinal bleeding caused by ruptured esophageal varices, ascites, and lower limb edema. She required intensive care and an endoscopic procedure to treat the gastrointestinal bleeding. The analysis of the differential diagnosis for chronic liver disease indicated she had a spontaneous splenorenal shunt. Ultrasound-guided biopsy revealed the patient had cirrhosis, as characteristically seen in individuals with ARPKD. She had no symptoms at discharge and was referred for review for a combined transplant.

In utero Partial Exchange Transfusion Combined with in utero Blood Transfusion for Prenatal Management of Twin Anemia-Polycythemia Sequence.

Monochorionic twin pregnancies are at risk of unique complications due to placental sharing and vascular connections between placental territories assigned for each twin. Twin anemia-polycythemia sequence (TAPS) is an infrequent but potentially dangerous complication of abnormal placental vascular connections. TAPS occurs due to very-small-caliber (< 1 mm) abnormal placental vascular connections which lead to chronic anemia in the donor twin and polycythemia in the recipient twin. TAPS may occur spontaneously or following fetoscopic laser photocoagulation of communicating placental vessels for twin-twin transfusion syndrome. One of the hallmarks of TAPS is the absence of polyhydramnios and oligohydramnios. The postnatal diagnosis is based on significant hemoglobin discrepancy between the twins. Middle cerebral artery peak systolic velocity Doppler ultrasound allows for the prenatal diagnosis of TAPS. The optimal prenatal treatment and intervention timing has not been established. Here, we report 3 spontaneous TAPS cases diagnosed and managed in the prenatal period with a combination of in utero blood transfusion for the anemic twin (donor) and in utero partial exchange transfusion for the polycythemic twin (recipient). These cases contribute to the limited outcome data of this underutilized method for the management of TAPS.

Understanding abnormal uterine artery Doppler waveforms: A novel computational model to explore potential causes within the utero-placental vasculature.

INTRODUCTION: Uterine artery (UtA) Doppler indices are one of the most commonly employed screening tests for pre-eclampsia worldwide. Abnormal indices appear to result from increased uterine vascular resistance, but anatomical complexity and lack of appropriate animal models mean that little is known about the relative contribution of each of the components of the uterine vasculature to the overall UtA Doppler waveform. Previous computational models suggested that trophoblast-mediated spiral artery remodeling has a dominant effect on the UtA Doppler waveform. However, these models did not incorporate the myometrial arterio-venous anastomoses, which have significant potential to affect utero-placental haemodynamics. METHODS: We present a more anatomically complete computational model, explicitly incorporating a structural description of each component of the uterine vasculature, and crucially including myometrial arterio-venous anastomoses as parallel pathways for blood-flow away from the placental bed. Wave transmission theory was applied to the network to predict UtA waveforms. RESULTS: Our model shows that high UtA resistance indices, combined with notching, reflect an abnormal remodeling of the entire uterine vasculature. Incomplete spiral artery remodeling alone is unlikely to cause abnormal UtA Doppler waveforms as increased resistance in these arteries can be 'buffered' by upstream anastomoses. Critically, our results indicate that the radial arteries, may have a more important effect on utero-placental flow dynamics, and the UtA Doppler waveform than previously thought. CONCLUSIONS: This model suggests that to appropriately interpret UtA Doppler waveforms they must be considered to be reflecting changes in the entire system, rather than just the spiral arteries.

Double inter-internal carotid artery communication through intercavernous anastomosis and posterior communicating artery associated with multiple intracranial artery segmental agenesis/aplasia.

Segmental internal carotid artery (ICA) and basilar artery (BA) agenesis/aplasia are rare vascular anomalies. We report an extremely rare case of combined ICA, BA, and A1 segmental absence presenting with double inter-ICA collateral communication through the intercavernous anastomosis and posterior communicating arteries. The patient presented with diplopia and transient ischemic attack. The pathogenesis of the anatomic anomalies and clinical symptoms are discussed.

Anastomosis of the external carotid artery and the V3 segment of the vertebral artery (presumed persistent second cervical intersegmental artery) diagnosed by CT angiography.

Congenital anastomosis of the external carotid (ECA) and vertebral (VA) arteries is extremely rare. We report a case of right ECA-VA anastomosis diagnosed by computed tomography (CT) angiography. The presumed dilated ascending pharyngeal artery coursed posteriorly and entered the C1 right transverse foramen. The proximal right VA was aplastic, and the C2 right transverse foramen was absent. Based on these findings, we diagnosed congenital anastomosis of the ECA and V3 segment of the VA, which we presumed to represent persistence of the second cervical intersegmental artery. Detection of rare variations of the vertebral arteries requires careful observation of CT angiography with bone images and source images, especially to identify the level of entry into the transverse foramen. Correct diagnosis of anastomosis is important when intravascular embolization or infusion chemotherapy or surgical ligation of the ECA is planned.

Arteriovenous fistulae of the filum terminale.

Filum terminale arteriovenous fistulae are a rare type of arteriovenous shunt generally characterized by a single direct communication between the artery of the filum terminale and a single draining vein. These intradural arteriovenous shunts are three times more common in men than women (mean age 55 years). Symptoms are related to venous congestion, vascular hypertension, and a putative chronic steal phenomenon which result in spinal cord ischemia and myelopathy. Interestingly, hemorrhage has never been reported as a mode of presentation. MRI demonstrates increased flow voids and T2 changes involving the conus and the lower spinal cord, and these findings are not dissimilar from those seen with the more common type 1 spinal dural arteriovenous fistulae. Thus conventional spinal angiography is necessary for a definitive diagnosis and to localize exactly the site of the fistula. Both surgical interruption of the fistula and endovascular embolization are safe and effective therapeutic modalities. However, because of the very small caliber of the feeding artery, endovascular therapy is often not feasible; and thus, surgery remains the method more commonly utilized for their treatment. Definitive treatment consists of obliteration of the direct arteriovenous shunt. In this review, we describe the anatomy, pathophysiology, clinical presentation, imaging, and treatment options of these less common intradural arteriovenous shunts.

Internal Carotid Artery Agenesis with an Intercavernous Anastomosis: A Rare Case.

BACKGROUND: Agenesis of the internal carotid artery (ICA) is a rare vascular anomaly that was first observed postmortem. Various anastomoses supply the distal vessels at the site of agenesis. Of these anastomoses, an intercavernous anastomosis is very rare. This paper presents a patient with ischemic stroke in whom we discovered left ICA agenesis and an ipsilateral intercavernous anastomosis. CASE: A 58-year-old man with a history of myocardial infarction and diabetes mellitus presented with sudden-onset difficulty in speaking, numbness on the left side of the face, and weakness of the left arm and leg. Neurological examination revealed dysarthria, left facial paralysis, left hemiparesis, and bilateral absence of the plantar reflexes. Diffusion-weighted magnetic resonance imaging showed a right middle cerebral artery (MCA) infarction. On cranial and cervical magnetic resonance angiography, the left ICA could not be seen distal to the bifurcation; the left MCA was supplied through an intercavernous anastomosis between the right ICA and the left ICA. Cranial computed tomography (CT) revealed the absence of the left carotid canal. Digital subtraction angiography led to a diagnosis of left ICA agenesis with an intercavernous anastomosis. The patient was discharged on acetylsalicylic acid and warfarin. CONCLUSION: ICA agenesis with an intercavernous anastomosis is a rare vascular anomaly that should be differentiated from secondary causes of ICA stenosis and occlusions by showing agenesis of the carotid canal on cranial CT.

Review of Experimental Modelling in Vascular Access for Hemodialysis.

This paper reviews applications of experimental modelling in vascular access for hemodialysis. Different techniques that are used in in-vitro experiments are bulk pressure and flow rate measurements, Laser Doppler Velocimetry and Vector Doppler Ultrasound point velocity measurements, and whole-field measurements such as Particle Image Velocimetry, Ultrasound Imaging Velocimetry, Colour Doppler Ultrasound, and Planar Laser Induced Fluorescence. Of these methods, the ultrasound techniques can also be used in-vivo, to provide realistic boundary conditions to in-vitro experiments or numerical simulations. In the reviewed work, experimental modelling is mainly used to support computational models, but also in some cases as a tool on its own. It is concluded that, to further advance the utility of computational modelling in vascular access research, a rigorous verification and validation procedure should be adopted. Experimental modelling can play an important role in both in-vitro validation, and the quantification of the accuracy, uncertainty, and reproducibility of in-vivo measurement methods.

Functional end-arterial circulation of the choroid assessed by using fat embolism and electric circuit simulation.

The discrepancy in the choroidal circulation between anatomy and function has remained unsolved for several decades. Postmortem cast studies revealed extensive anastomotic channels, but angiographic studies indicated end-arterial circulation. We carried out experimental fat embolism in cats and electric circuit simulation. Perfusion defects were observed in two categories. In the scatter perfusion defects suggesting an embolism at the terminal arterioles, fluorescein dye filled the non-perfused lobule slowly from the adjacent perfused lobule. In the segmental perfusion defects suggesting occlusion of the posterior ciliary arteries, the hypofluorescent segment became perfused by spontaneous resolution of the embolism without subsequent smaller infarction. The angiographic findings could be simulated with an electric circuit. Although electric currents flowed to the disconnected lobule, the level was very low compared with that of the connected ones. The choroid appeared to be composed of multiple sectors with no anastomosis to other sectors, but to have its own anastomotic arterioles in each sector. Blood flows through the continuous choriocapillaris bed in an end-arterial nature functionally to follow a pressure gradient due to the drainage through the collector venule.

Relationship between quantitative and descriptive methods of studying blood flow through intrapulmonary arteriovenous anastomoses during exercise.

Several methods exist to study intrapulmonary arteriovenous anastomoses (IPAVA) in humans. Transthoracic saline contrast echocardiography (TTSCE), i.e., bubble scores, is minimally-invasive, but cannot be used to quantify the magnitude of blood flow through IPAVA (QIPAVA). Radiolabeled macroaggregates of albumin (99mTc-MAA) have been used to quantify QIPAVA in humans, but this requires injection of radioactive particles. Previous work has shown agreement between 99mTc-MAA and TTSCE, but this has not been tested simultaneously in the same group of subjects. Thus, the purpose of this study was to determine if there was a relationship between QIPAVA quantified with 99mTc-MAA and bubble scores obtained with TTSCE. To test this, we used 99mTc-MAA and TTSCE to quantify and detect QIPAVA at rest and during exercise in humans. QIPAVA significantly increased from rest to exercise using 99mTc-MAA and TTSCE and there was a moderately-strong, but significant relationship between methods. Our data suggest that high bubble scores generally correspond with large QIPAVA quantified with 99mTc-MAA during exercise.