Vascular anastomoses in intrauterine growth in monochorionic twins.

Objectives To evaluate the impact of placental anastomoses on the intrauterine growth of monochorionic (MC) twins. Methods A prospective study was conducted in a group of 53 MC twins. Intrapartally umbilical cords were clamped to identify placental sides corresponding to each twin. The postnatal dye injection technique was administered to evaluate vascular anastomoses, their number and type and visualize placental territory sharing patterns. Data from digital analysis were correlated with obstetrical follow-up. Results Vascular anastomoses were revealed in 88.7% of cases. Arteriovenous (AV) anastomoses occurred in 75.4% and arterioarterial (AA) in 71.1% while venovenous (VV) in 26.4%. In the subgroup of MC twins without placental anastomoses, significantly higher birthweight difference and discordance were revealed when compared to MC twins without anastomoses (382.0 vs. 22 g; P = 0.03 and 49.14% vs. 16.02%; P = 0.03). On the other hand, in subgroups of MC twins with at least one AA anastomosis, twins' birthweights were similar (p = ns) despite significantly higher placental territory sharing discordance (30.44% vs. 15.81%; P = 0.31). Conclusions Vascular anastomoses have a major impact on the intrauterine growth of MC twins. In certain cases, they may cause specific complications; however, in general, they regulate intertwin blood exchange and may compensate unequal placental territory.

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.

Incidence of and Risk Factors for Residual Anastomoses in Twin-Twin Transfusion Syndrome Treated with Laser Surgery: A 15-Year Single-Center Experience.

OBJECTIVES: To evaluate the incidence of residual anastomoses (RA) after laser therapy for twin-twin transfusion syndrome (TTS) and investigate risk factors for incomplete laser surgery. MATERIAL AND METHODS: All available TTS placentas treated with laser at our center between 2002 and 2016 were injected with color dye to assess the presence of RA. We evaluated the incidence of RA over the past 15 years by dividing the cohort into three time periods, and studied the association with risk factors and neonatal outcome. RESULTS: Overall, RA were detected in 21.0% (78/371) of placentas. The incidence of RA decreased from 38.8% (26/67) in the initial period to 11.7% (16/137) in the most recent period (p < 0.001). On multivariate analysis, several risk factors were independently associated with the risk of RA, including Solomon laser technique (odds ratio [OR] 0.17, 95% CI 0.09-0.33) and estimation of surgical success (OR 19.28, 95% CI 8.17-45.49). Premature delivery and neonatal morbidity occurred more often in TTS cases with RA. CONCLUSIONS: The incidence of RA after laser therapy for TTS decreased significantly in the past 15 years and is now below 15% due to the use of the Solomon technique.

Bubble and macroaggregate methods differ in detection of blood flow through intrapulmonary arteriovenous anastomoses in upright and supine hypoxia in humans.

Blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) increases in healthy humans breathing hypoxic gas and is potentially dependent on body position. Previous work in subjects breathing room air has shown an effect of body position when Q̇IPAVA is detected with transthoracic saline contrast echocardiography (TTSCE). However, the potential effect of body position on Q̇IPAVA has not been investigated when subjects are breathing hypoxic gas or with a technique capable of quantifying Q̇IPAVA. Thus the purpose of this study was to quantify the effect of body position on Q̇IPAVA when breathing normoxic and hypoxic gas at rest. We studied Q̇IPAVA with TTSCE and quantified Q̇IPAVA with filtered technetium-99m-labeled macroaggregates of albumin (99mTc-MAA) in seven healthy men breathing normoxic and hypoxic (12% O2) gas at rest while supine and upright. On the basis of previous work using TTSCE, we hypothesized that the quantified Q̇IPAVA would be greatest with hypoxia in the supine position. We found that Q̇IPAVA quantified with 99mTc-MAA significantly increased while subjects breathed hypoxic gas in both supine and upright body positions (ΔQ̇IPAVA = 0.7 ± 0.4 vs. 2.5 ± 1.1% of cardiac output, respectively). Q̇IPAVA detected with TTSCE increased from normoxia in supine hypoxia but not in upright hypoxia (median hypoxia bubble score of 2 vs. 0, respectively). Surprisingly, Q̇IPAVA magnitude was greatest in upright hypoxia, when Q̇IPAVA was undetectable with TTSCE. These findings suggest that the relationship between TTSCE and 99mTc-MAA is more complex than previously appreciated, perhaps because of the different physical properties of bubbles and MAA in solution. NEW & NOTEWORTHY Using saline contrast bubbles and radiolabeled macroaggregrates (MAA), we detected and quantified, respectively, hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) in supine and upright body positions in healthy men. Upright hypoxia resulted in the largest magnitude of Q̇IPAVA quantified with MAA but the lowest Q̇IPAVA detected with saline contrast bubbles. These surprising results suggest that the differences in physical properties between saline contrast bubbles and MAA in blood may affect their behavior in vivo.

Substitution-rate based screening model to assess stenosis progression in experimental stenotic arteriovenous grafts.

An arteriovenous graft (AVG) has a higher patency rate in stenosis progression at the venous anastomosis site, which causes coexisting inflow and outflow stenoses. This leads to increases in blood pressure, flow velocity, and flow resistance, resulting in hemodialysis (HD) vascular access dysfunction from early clots and thrombosis to the progression of coexisting stenoses. To prevent vascular access complications such as inflow or outflow stenoses, this study proposes a novel examination method in an experimental AVG system using a substitution-rate based screening model. In our practical measurements, we found that inflow and outflow channeled through a narrowed access indicated both pressure and resistance differences as the degree of stenosis (DOS) gradually increased. A substitution-rate matrix was conducted to replace bilateral pressure variations, while a transition probability matrix was calculated. Differences in transition probabilities were then used to distinguish between normal conditions and flow instabilities using the distance estimation method. The joint probability decayed from < 0.81 to 0.00 could be specified to identify the progression in stenosis levels from a DOS% = 50.0-95.0%. Average joint probabilities were found to be inversely related with the DOS using a non-linear regression (R>2 0.90). Hence, the joint probability could be specified as a critical threshold, < 0.81, to identify the severity stenosis level, DOS% ⩾ 70%, in the assessment of coexisting inflow and outflow stenoses. Experimental results suggest that the proposed model is superior to hemodynamic analysis and traditional intelligent method, and can be used for dysfunction screening during HD treatment.

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.

Hemodynamic Parameters and Early Intimal Thickening in Branching Blood Vessels.

Intimal thickening due to atherosclerotic lesions or intimal hyperplasia in medium to large blood vessels is a major contributor to heart disease, the leading cause of death in the Western World. Balloon angioplasty with stenting, bypass surgery, and endarterectomy (with or without patch reconstruction) are some of the techniques currently applied to occluded blood vessels. On the basis of the preponderance of clinical evidence that disturbed flow patterns play a key role in the onset and progression of atherosclerosis and intimal hyperplasia, it is of interest to analyze suitable hemodynamic wall parameters that indicate susceptible sites of intimal thickening and/or favorable conditions for thrombi formation. These parameters, based on the wall shear stress, wall pressure, or particle deposition, are applied to interpret experimental/clinical observations of intimal thickening. Utilizing the parameters as "indicator" functions, internal branching blood vessel geometries are analyzed and possibly altered for different purposes: early detection of possibly highly stenosed vessel segments, prediction of future disease progression, and vessel redesign to potentially improve long-term patency rates. At the present time, the focus is on the identification of susceptible sites in branching blood vessels and their subsequent redesign, employing hemodynamic wall parameters. Specifically, the time-averaged wall shear stress (WSS), its spatial gradient (WSSG), the oscillatory shear index (OSI), and the wall shear stress angle gradient (WSSAG) are compared with experimental data for an aortoceliac junction. Then, the OSI, wall particle density (WPD), and WSSAG are segmentally averaged for different carotid artery bifurcations and compared with clinical data of intimal thickening. The third branching blood vessel under consideration is the graft-to-vein anastomosis of a vascular access graft Suggested redesigns reduce several hemodynamic parameters (i.e., the WSSG, WSSAG, and normal pressure gradient [NPG]), thereby reducing the likelihood of restenosis, especially near the critical toe region.

Intrapulmonary arteriovenous anastomoses in humans with chronic obstructive pulmonary disease: implications for cryptogenic stroke?

What is the central question of this study? Do individuals with chronic obstructive pulmonary disease have blood flow through intrapulmonary arteriovenous anastomoses at rest or during exercise? What is the main finding and its importance? Individuals with chronic obstructive pulmonary disease have a greater prevalence of blood flow through intrapulmonary arteriovenous anastomoses at rest than age-matched control subjects. Given that the intrapulmonary arteriovenous anastomoses are large enough to permit venous emboli to pass into the arterial circulation, patients with chronic obstructive pulmonary disease and an elevated risk of thrombus formation may be at risk of intrapulmonary arteriovenous anastomosis-facilitated embolic injury (e.g. stroke or transient ischaemic attack). The pulmonary capillaries prevent stroke by filtering venous emboli from the circulation. Intrapulmonary arteriovenous anastomoses are large-diameter (≥50 µm) vascular connections in the lung that may compromise the integrity of the pulmonary capillary filter and have recently been linked to cryptogenic stroke and transient ischaemic attack. Prothrombotic populations, such as individuals with chronic obstructive pulmonary disease (COPD), may be at increased risk of stroke and transient ischaemic attack facilitated by intrapulmonary arteriovenous anastomoses, but the prevalence and degree of blood flow through intrapulmonary arteriovenous anastomoses in this population has not been fully examined and compared with age-matched healthy control subjects. We used saline contrast echocardiography to assess blood flow through intrapulmonary arteriovenous anastomoses at rest (n = 29 COPD and 19 control subjects) and during exercise (n = 10 COPD and 10 control subjects) in subjects with COPD and age-matched healthy control subjects. Blood flow through intrapulmonary arteriovenous anastomoses was detected in 23% of subjects with COPD at rest and was significantly higher compared with age-matched healthy control subjects. Blood flow through intrapulmonary arteriovenous anastomoses at rest was reduced or eliminated in subjects with COPD after breathing hyperoxic gas. Sixty per cent of subjects with COPD who did not have blood flow through the intrapulmonary arteriovenous anastomoses at rest had blood flow through them during exercise. The combination of blood flow through intrapulmonary arteriovenous anastomoses and potential for thrombus formation in individuals with COPD may permit venous emboli to pass into the arterial circulation and cause stroke and transient ischaemic attack. Breathing supplemental oxygen may reduce this risk in COPD. The link between blood flow through intrapulmonary arteriovenous anastomoses, stroke and transient ischaemic attack is worthy of future investigation in COPD and other populations.

Evolution of Stage 1 Twin-to-Twin Transfusion Syndrome (TTTS): Systematic Review and Meta-Analysis.

OBJECTIVES: The natural history of stage 1 Twin-to-twin transfusion syndrome (TTTS) remains unclear and its optimal management is yet to be established. The main aims of this meta-analysis were to quantify the incidence of progression in stage 1 TTTS and to ascertain survival in these pregnancies. METHODS: MEDLINE, EMBASE, and The Cochrane Library were searched. Reference lists within each article were hand-searched for additional reports. The outcomes included incidence of progression and survival in stage 1 TTTS. Randomized controlled trials, cohort and case-control studies were included. Case reports, studies including three or fewer cases of stage 1 TTTS, and editorials were excluded. Proportion meta-analysis was used for analysis (Registration number: CRD42016036190). RESULTS: The search yielded 3,085 citations; 18 studies were included in the review (172 pregnancies to assess progression and 433 pregnancies to assess the survival). The pooled incidence of progression in stage 1 TTTS was 27% [95% CI 16-39%]. The pooled overall survival, double survival and at least one survival in the pregnancies managed expectantly were 79% [95% CI 62-92%], 70% [95% CI 54-84%] and 87% [95% CI 69-98%], respectively. In those undergoing amnioreduction, the corresponding figures were 77% [95% CI 68-85%], 67% [95% CI 57-76%] and 86% [95% CI 76-94%], respectively. The survival rates were 68% [95% CI 54-81%], 54% [95% CI 36-72%], and 81% [95% CI 69-90%], when laser surgery was performed. CONCLUSIONS: The optimal initial management of stage 1 TTTS remains in equipoise. The ongoing randomized trial comparing immediate laser surgery versus conservative management should provide a definitive answer.

The History of Treatment of Twin-to-Twin Transfusion Syndrome.

Historical suggestions of twin-to-twin transfusion syndrome (TTTS) date back to the early 17th century. Placental anastomoses were first reported in 1687; however, it was Schatz who first identified their importance in 1875. He recognized 'the area of transfusion' within the 'villous district' of the placenta, which he named the 'third circulation'. This article describes how the management of TTTS has evolved as we have gained a more sophisticated understanding and appreciation of the complex vascular anastomoses that exist in monochorionic twin placentae. Currently, fetosopic laser occlusion is the preferred treatment option for TTTS.

Laser Treatment of Twin-to-Twin Transfusion Syndrome.

OBJECTIVE: Laser ablation of all placental vascular anastomoses is the optimal treatment for twin-twin transfusion syndrome (TTTS). However, two important controversies are apparent in the literature: (a) a gap between concept and performance, and (b) controversy regarding whether all the anastomoses can be identified endoscopically and whether blind lasering of healthy placenta is justified. The purpose of this article is: (a) to address the potential source of the gap between concept and performance by analyzing the fundamental steps needed to successfully accomplish the surgery, and (b) to discuss the resulting competency benchmarks reported with the different surgical techniques. MATERIALS AND METHODS: Laser surgery for TTTS can be broken down into two fundamental steps: (1) endoscopic identification of the placental vascular anastomoses, (2) laser ablation of the anastomoses. The two steps are not synonymous: (a) regarding the endoscopic identification of the anastomoses, the non-selective technique is based upon lasering all vessels crossing the dividing membrane, whether anastomotic or not. The selective technique identifies and lasers only placental vascular anastomoses. The Solomon technique is based on the theory that not all anastomoses are endoscopically visible and thus involves lasering healthy areas of the placenta between lasered anastomoses, (b) regarding the actual laser ablation of the anastomoses, successful completion of the surgery (i.e., lasering all the anastomoses) can be measured by the rate of persistent or reverse TTTS (PRTTTS) and how often a selective technique can be achieved. Articles representing the different techniques are discussed. RESULTS: The non-selective technique is associated with the lowest double survival rate (35%), compared with 60-75% of the Solomon or the Quintero selective techniques. The Solomon technique is associated with a 20% rate of residual patent placental vascular anastomoses, compared to 3.5-5% for the selective technique (p < .05). Both the Solomon and the selective technique are associated with a 1% risk of PRTTTS. Adequate placental assessment is highest with the selective technique (99%) compared with the Solomon (80%) or the 'standard' (60%) techniques (p < .05). A surgical performance index is proposed. CONCLUSION: The Quintero selective technique was associated with the highest rate of successful ablation and lowest rate of PRTTTS. The Solomon technique represents a historical backward movement in the identification of placental vascular anastomoses and is associated with higher rate of residual patent vascular communications. The reported outcomes of the Quintero selective technique do not lend support to the existence of invisible anastomoses or justify lasering healthy placental tissue.

Decreased arterial PO2, not O2 content, increases blood flow through intrapulmonary arteriovenous anastomoses at rest.

KEY POINTS: The mechanism(s) that regulate hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) are currently unknown. Our previous work has demonstrated that the mechanism of hypoxia-induced QIPAVA is not simply increased cardiac output, pulmonary artery systolic pressure or sympathetic nervous system activity and, instead, it may be a result of hypoxaemia directly. To determine whether it is reduced arterial PO2 (PaO2) or O2 content (CaO2) that causes hypoxia-induced QIPAVA , individuals were instructed to breathe room air and three levels of hypoxic gas at rest before (control) and after CaO2 was reduced by 10% by lowering the haemoglobin concentration (isovolaemic haemodilution; Low [Hb]). QIPAVA , assessed by transthoracic saline contrast echocardiography, significantly increased as PaO2 decreased and, despite reduced CaO2 (via isovolaemic haemodilution), was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA , although where and how this is detected remains unknown. ABSTRACT: Alveolar hypoxia causes increased blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) in healthy humans at rest. However, it is unknown whether the stimulus regulating hypoxia-induced QIPAVA is decreased arterial PO2 (PaO2) or O2 content (CaO2). CaO2 is known to regulate blood flow in the systemic circulation and it is suggested that IPAVA may be regulated similar to the systemic vasculature. Thus, we hypothesized that reduced CaO2 would be the stimulus for hypoxia-induced QIPAVA . Blood volume (BV) was measured using the optimized carbon monoxide rebreathing method in 10 individuals. Less than 5 days later, subjects breathed room air, as well as 18%, 14% and 12.5% O2 , for 30 min each, in a randomized order, before (CON) and after isovolaemic haemodilution (10% of BV withdrawn and replaced with an equal volume of 5% human serum albumin-saline mixture) to reduce [Hb] (Low [Hb]). PaO2 was measured at the end of each condition and QIPAVA was assessed using transthoracic saline contrast echocardiography. [Hb] was reduced from 14.2 ± 0.8 to 12.8 ± 0.7 g dl(-1) (10 ± 2% reduction) from CON to Low [Hb] conditions. PaO2 was no different between CON and Low [Hb], although CaO2 was 10.4%, 9.2% and 9.8% lower at 18%, 14% and 12.5% O2 , respectively. QIPAVA significantly increased as PaO2 decreased and, despite reduced CaO2, was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA . Whether the low PO2 is detected at the carotid body, airway and/or the vasculature remains unknown.

Resting arterial hypoxaemia in subjects with chronic heart failure, pulmonary hypertension and patent foramen ovale.

NEW FINDINGS: What is the central question of this study? Does a patent foramen ovale contribute to resting arterial hypoxaemia, defined as arterial oxygen saturation <95%, in subjects with chronic heart failure with or without pulmonary arterial hypertension? What is the main finding and its importance? The presence of a patent foramen ovale contributed to resting arterial hypoxaemia only in subjects with chronic heart failure with pulmonary arterial hypertension. These data suggest that the presence of a patent foramen ovale should be considered in chronic heart failure patients with arterial hypoxaemia and pulmonary hypertension. The roles of intrapulmonary and intracardiac shunt in contributing to arterial hypoxaemia at rest in subjects with chronic heart failure (CHF) have not been well investigated. We hypothesized that blood flow through intrapulmonary arteriovenous anastomoses (Q̇ IPAVA ) and/or patent foramen ovale (Q̇ PFO ) could potentially contribute to arterial hypoxaemia and, with pulmonary hypertension (PH) secondary to CHF, this contribution may be exacerbated. Fifty-six subjects with CHF (New York Heart Association Classes I-III), with (+) or without (-) PH [defined as peak tricuspid regurgitation velocity ≥2.9 m s(-1) (CHF PH+, n = 32) and peak tricuspid regurgitation velocity ≤2.8 m s(-1) (CHF PH-, n = 24)], underwent arterial blood gas analysis and transthoracic saline contrast echocardiography concomitant with transcranial Doppler to detect Q̇ IPAVA and Q̇ PFO . Seventeen of 56 subjects with CHF (30%) had Q̇ PFO , but only four of 56 subjects with CHF had Q̇ IPAVA (7%), both similar to age- and sex-matched control subjects. Mean arterial oxygen saturation (SaO2) was lower in subjects with Q̇ PFO . Only CHF PH+ subjects with Q̇ PFO had arterial hypoxaemia (mean SaO2 <95%). Bubble scores assessed using transthoracic saline contrast echocardiography were correlated with microembolic signals detected with transcranial Doppler in subjects with Q̇ PFO . Significant Q̇ IPAVA was not present in either CHF PH+ or PH- subjects, suggesting that Q̇ IPAVA is not dependent on increased pulmonary pressure and does not contribute significantly to arterial hypoxaemia in older subjects with CHF. Given that SaO2 was lower in all subjects with CHF who had Q̇ PFO compared with those without Q̇ PFO , a patent foramen ovale should be considered when determining potential causes of arterial hypoxaemia, because Q̇ PFO was present in 30% of these subjects.

Transitional Flow in the Venous Side of Patient-Specific Arteriovenous Fistulae for Hemodialysis.

Arteriovenous fistula (AVF) is the first choice for providing vascular access for hemodialysis patients, but maintaining its patency is challenging. AVF failure is primarily due to development of neointimal hyperplasia (NH) and subsequent stenosis. Using idealized models of AVF we previously suggested that reciprocating hemodynamic wall shear is implicated in vessel stenosis. The aim of the present study was to investigate local hemodynamics in patient-specific side-to-end AVF. We reconstructed realistic geometrical models of four AVFs from magnetic resonance images acquired in a previous clinical study. High-resolution computational fluid dynamics simulations using patient-specific blood rheology and flow boundary conditions were performed. We then characterized the flow field and categorized disturbed flow areas by means of established hemodynamic wall parameters. In all AVF, either in upper or lower arm location, we consistently observed transitional laminar to turbulent-like flow developing in the juxta-anastomotic vein and damping towards the venous outflow, but not in the proximal artery. High-frequency fluctuations of the velocity vectors in these areas result in eddies that induce similar oscillations of wall shear stress vector. This condition may importantly impair the physiological response of endothelial cells to blood flow and be responsible for NH formation in newly created AVF.

Central iliac arteriovenous anastomosis for hypertension: targeting mechanical aspects of the circulation.

Raised blood pressure is the leading attributable risk factor for global morbidity and mortality. Real world data demonstrates that half of treated patients are at elevated cardiovascular risk because of inadequately controlled BP. In addition to pharmacotherapy, certain interventional strategies to reduce blood pressure and cardiovascular risk in hypertension can be considered according to international guidelines. One of the newer technologies entering this field is a proprietary arteriovenous coupler device that forms a fixed flow arteriovenous conduit in the central vasculature. In this review, we examine the development of and rationale for the creation of a central arteriovenous anastomosis in patients with hypertension and review the proposed mechanisms by which it may ameliorate hypertension. We critically review the clinical trial evidence base to date and postulate on future therapeutic directions.

Very Few Exercise-Induced Arterialized Gas Bubbles Reach the Cerebral Vasculature.

INTRODUCTION: Arterialization of venous gas emboli (VGE) formed after surfacing from SCUBA diving can become arterial gas emboli (AGE) through intrapulmonary arterial-venous anastomoses that open with exercise. METHODS: We recruited twenty patent foramen ovale-negative SCUBA divers and conducted a field and a laboratory study with the aim of investigating the appearance of AGE in intracranial vessels. At the field, they performed a single dive to a depth of 18-m sea water with a 47-min bottom time and a direct ascent to the surface. Transthoracic echocardiography was used to score VGE and AGE, and transcranial Doppler was used to visualize middle and posterior cerebral arteries with automated objective bubble detection. Observations were conducted for 45-min after dive at rest and at the laboratory after agitated saline injection at rest and throughout an incremental cycle supine exercise test until exhaustion and for 10 min of recovery. RESULTS: After resurfacing, all divers presented endogenous VGE and arterialization was present in three divers. Saline contrast injection led to AGE in nine of 19 subjects at rest. AGE that reached the cerebral arteries after dive were recorded in two divers at 60 W, three at 90 W, five at 120 W, six at 150 W, and four at 180 W and in three, four, five, nine, and nine, respectively, after saline contrast injection in the laboratory. All divers had AGE grades of 1 or 2, and only single AGE reached the cerebral vasculature. CONCLUSIONS: These data suggest that few emboli of venous origin reach the brain through exercise-induced intrapulmonary arterial-venous anastomoses but cerebral embolization is not high risk in the studied population.

Different ophthalmic artery origins: Embryology and clinical significance.

This retrospective study gives a summary of ophthalmic artery (OA) variations to serve as guidelines for surgical interventionists and trainees. Pubmed and Medline searches were conducted. The OA usually arises intradurally (superomedial, anteromedial, or rarely superolateral) from the internal carotid artery (ICA). Rare extradural origin (primitive dorsal OA) (PDOA) remnant and extremely rare interdural origin (primitive ventral OA) (PVOA) remnant are of significance when sectioning the dural ring. Rarely, a persistent PDOA with ICA origin, or a PDOA remnant with inferolateral trunk origin, enters the orbit via the superior orbital fissure (SOF) for sole or partial orbital supply. Extremely rare, the PDOA and PVOA persist and form double OAs that arise from the ICA and run via the SOF and optic foramen. Occasionally, the OA arises from the middle meningeal artery (MMA), when both the PDOA and VDOA regress and enter the orbit via the SOF. Sole orbital supply via the external carotid artery (ECA), i.e. meningo-ophthalmic artery and/or MMA branches, or dual OAs (ECA and ICA origins) may occur. Other rare OA origins include anterior or posterior communicating artery; anterior or middle cerebral artery; basilar artery; posterior inferior cerebellar artery; and the carotid bifurcation. Primitive arteries (persistent or remnant), and/or abnormal anastomoses play pivotal roles in manifestations of OA variations. Of clinical importance are orbital collateral routes and dangerous extracranial-intracranial anastomoses. Awareness of OA origins and collateral routes is imperative for transarterial embolizations or infusion chemotherapy in the ECA territory to prevent visual complications.

MEMS-based handheld fourier domain Doppler optical coherence tomography for intraoperative microvascular anastomosis imaging.

PURPOSE: To demonstrate the feasibility of a miniature handheld optical coherence tomography (OCT) imager for real time intraoperative vascular patency evaluation in the setting of super-microsurgical vessel anastomosis. METHODS: A novel handheld imager Fourier domain Doppler optical coherence tomography based on a 1.3-µm central wavelength swept source for extravascular imaging was developed. The imager was minimized through the adoption of a 2.4-mm diameter microelectromechanical systems (MEMS) scanning mirror, additionally a 12.7-mm diameter lens system was designed and combined with the MEMS mirror to achieve a small form factor that optimize functionality as a handheld extravascular OCT imager. To evaluate in-vivo applicability, super-microsurgical vessel anastomosis was performed in a mouse femoral vessel cut and repair model employing conventional interrupted suture technique as well as a novel non-suture cuff technique. Vascular anastomosis patency after clinically successful repair was evaluated using the novel handheld OCT imager. RESULTS: With an adjustable lateral image field of view up to 1.5 mm by 1.5 mm, high-resolution simultaneous structural and flow imaging of the blood vessels were successfully acquired for BALB/C mouse after orthotopic hind limb transplantation using a non-suture cuff technique and BALB/C mouse after femoral artery anastomosis using a suture technique. We experimentally quantify the axial and lateral resolution of the OCT to be 12.6 µm in air and 17.5 µm respectively. The OCT has a sensitivity of 84 dB and sensitivity roll-off of 5.7 dB/mm over an imaging range of 5 mm. Imaging with a frame rate of 36 Hz for an image size of 1000(lateral)×512(axial) pixels using a 50,000 A-lines per second swept source was achieved. Quantitative vessel lumen patency, lumen narrowing and thrombosis analysis were performed based on acquired structure and Doppler images. CONCLUSIONS: A miniature handheld OCT imager that can be used for intraoperative evaluation of microvascular anastomosis was successfully demonstrated.

Monochorionic twin placentas: injection technique and analysis / Placentas monocoriónicas: técnicas de inyección y análisis

Careful placenta examination and injection studies are crucial to understand the differences between the various complications in monochorionic (MC) pregnancies. In this review, we will first describe an accurate and simple method of placental injection and then discuss the placental characteristics of normal MC, twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS), selective intrauterine growth restriction (sIUGR), monoamniotic (MA) and other special cases (AU)

El examen cuidadoso de la placenta y los estudios de inyección son cruciales para comprender las diferencias existentes entre las diversas complicaciones de los embarazos MC. En esta revisión, vamos a describir primero un método preciso y simple de inyección placentaria y, posteriormente, abordaremos las características de una placenta normal en MC, el síndrome de transfusión fetal-fetal (STFF), la secuencia anemia-policitemia (SAP), la restricción del crecimiento intrauterino selectivo (CIRs), la placenta monoamniótica (MA) y otros casos especiales (AU)

Dysfunctional arteriovenous anastomoses in hands of systemic sclerosis patients with digital ulcers.

OBJECTIVES: Previous studies indicate that the arteriovenous anastomoses (AVAs) and the arterioles with the nutritive flow are involved in the pathophysiologic process disturbing hand blood flow in systemic sclerosis (SSc). However, impact of different part of the microvascular system involved in digital ulcers (DU) is not well known. Here, we aimed to assess the vasomotor activity of the AVAs in the hands of patients with and without DU in SSc. METHODS: Simultaneous recordings were made of laser Doppler flux in the finger pulp and thenar eminence, together with ipsilateral radial artery blood velocity and mean arterial blood pressure (MAP) in 22 non-smoking SSc patients and 13 aged-matched healthy controls. RESULTS: AVA responses in the finger pulp to spontaneous vasoconstrictor nerve impulses were abolished in 64% of the SSc patients. Correlation and cross-spectra analysis showed positive correlation between blood flow changes and MAP changes, indicating a passive vascular bed in the SSc finger pulp with blood flow variations depending on short-term variability in MAP. Dysfunctional AVAs were identified in all the patients with a history of DU (n=8), while none of the patients with normal AVA function had episodes of DU (n=8) (p= 0.017). CONCLUSIONS: We found that in SSc patients with DU there is a dysfunction of the AVAs of the finger pulp. This proof-of-concept study supports the notion that AVA dysfunction may play a critical role in SSc related DU. AVA dysfunction may be a part of autonomic dysfunction in SSc.