Collateral Flow Research Articles

Arterial highways of the foot of the American raccoon (Procyon lotor)

The vascular system is one of the integrating systems of the human and animal body. The course and branching of the vessels of various areas of the body follows general patterns. However, the variability of the vascular bed is quite high even within a single species of animal. The lack of data on both the topography and the peculiarities of arterial branching makes it difficult to carry out diagnostic and therapeutic manipulations. In addition, the data obtained during the study significantly enrich the available information on the comparative anatomy of the vascular bed. The purpose of the study is to study the main arterial arteries of the American raccoon foot area, to give them a morphometric characteristic. The research was carried out on 4 corpses of an American raccoon, delivered to the Department of Animal Anatomy of the St. Petersburg State University of Veterinary Medicine from veterinary clinics. Classical methods were chosen as research methods: fine anatomical dissection, morphometry, photographing and vasorentgenography. During the study, it was found that two arterial highways are distinguished on the foot of the American raccoon. The dorsal trunk is represented by the dorsal artery of the foot, the plantar trunk is represented by the middle plantar artery. The dorsal artery of the foot passes into the arc artery – the first anastomosis that unites the vessels of the two highways. The middle plantar artery gives rise to the second and third plantar metatarsal arteries and participates in the formation of a deep plantar arch, which is the second major anastomosis of the foot area. Axial and non-axial finger arteries also form collateral blood flow. Analyzing the obtained morphometric data of arterial highways, it follows to conclude that the plantar surface highways have the largest diameter. Thus, the diameter of the middle plantar artery is 1.72 times higher than the same parameter of the dorsal artery of the foot. The largest total diameter is characteristic of the arteries located in the metatarsal region, the smallest in the area of the metatarsal.

Comprehensive insights into lumbar epidural varicose veins: Three clinical cases and surgical strategies.

Lumbar epidural varicose veins (LEVs) present a challenging clinical scenario with limited literature. This series addresses the scarcity of comprehensive understanding, emphasizing the need for nuanced exploration. Varied prevalence estimates and clinical oversights underscore the urgency for a standardized approach to surgical interventions. We present three diverse clinical cases: (1) segmental varicose veins causing radicular pain, (2) local varicosities leading to lower paraparesis, and (3) widespread varicose veins with prolonged symptoms. Surgical tactics involved targeted coagulation, crossing of veins, and preservation of collateral blood flow. Advanced imaging techniques guided interventions. Tailoring interventions based on varicose vein subtype, preserving collateral flow, and adopting a staged postoperative approach contribute to successful outcomes. This series provides valuable insights into LEV management, emphasizing the significance of advanced imaging in diagnosis and surgical planning.

The effects of stress hyperglycemia in diabetic and nondiabetic patients with large vessel occlusions undergoing mechanical thrombectomy.

Diabetes and hyperglycemia are major risk factors that can increase infarction volume and contribute to poor functional status. Our study aim was to investigate the effect of stress hyperglycemia on various safety and efficacy outcomes in patients with large vessel occlusions (LVOs) undergoing mechanical thrombectomy (MT) with or without diabetes. A retrospective analysis of consecutive LVO patient data treated with MT at a Comprehensive Stroke Center in the Mid-South was conducted. Adult patients with LVO on computed tomography angiography (CTA) and treated with MT within 24 h of symptom onset were included. The primary outcome was to determine if there was an association in collateral flow or infarct size in the setting of hyperglycemia. Secondary outcomes included National Institute of Health Sciences Score (NIHSS) and Modified Rankin Score (mRS). A total of 450 patients underwent MT, out of which 433 had baseline hemoglobin A1c recorded: mean age: 64 ± 15 years, 47% women, pretreatment NIHSS median 15 points (interquartile range 10-19), 323 (75%) with good collaterals grades >2 on multiphasic CTA, 326 (75%) were non-diabetic, and 107 (25%) were diabetic. Nondiabetics with stress hyperglycemia had a tendency toward higher pre-treatment NIHSS scores (mean 17.5 ± 7.6, P = 0.02) and at 24-h (12.9 ± 9.0, P = 0.02), poor collaterals (multiphasic CTA score ≥2; 21.4% vs. 34.5%, P = 0.02), larger infarct volumes (50.7 ± 63.6 vs. 24.4 ± 33.8 cc, P < 0.0001), and had poorer functional outcomes (good mRS 0-2 47.7% vs. good mRS 0-2 36.8%) when compared to nondiabetics without stress hyperglycemia. For every 1 mg/dL increase in admission blood glucose, there was a 0.3 cc increase in infarct volume (95% confidence intervals for β =0.2-0.4; P < 0.0001) after adjusting for the final thrombolysis in cerebral infarction score. LVO patients with stress hyperglycemia without previously diagnosed diabetes had more severe strokes, developed larger infarct volumes, poorer collaterals, and had worse functional outcomes at 90 days post-MT. In addition, LVO patients with diabetes and stress hyperglycemia exhibited more passes during MT and worse functional outcomes.

405 The Impact of Cerebral Revascularization on Pial Collateral Flow in Patients With Moyamoya Disease Using Quantitative Magnetic Resonance Angiography

INTRODUCTION: Moyamoya disease (MMD) is a chronic steno-occlusive disease primarily of the anterior circulation leading to significant pial collateralization. Changes in the distribution of intracranial blood flow after revascularization surgery are not well understood. METHODS: We conducted a retrospective chart review of 46 patients with unilateral MMD who underwent cerebral revascularization from 2011-2019. Patients who underwent pre- and post- QMRA NOVA were included in the study. Flow was measured at the M1 segment of the middle cerebral artery (MCA), P2 segment of the posterior cerebral artery (PCA), and A2 segment of the anterior cerebral artery (ACA). Pial collaterals were defined as the sum of (A2+P2) flow. Total hemispheric flow was calculated as (M1+PCA+A2) pre-operatively and (M1+PCA+A2+Bypass) post-operatively, with the incorporation of the bypass graft. RESULTS: A total of 46 patients with unilateral MMD underwent revascularization with pre and post QMRA. Total intracranial flow at baseline prior to revascularization was lower in the side of disease (214.9 ml/min vs. 269.1 ml/min). Total intracranial flow at baseline after revascularization remained lower on the ipsilateral side of disease with an increased flow in the contralateral healthy side (211.7 ml/min vs 286.1 ml/min). Pre-bypass there was a higher flow through pial collaterals on the ipsilateral diseased side (183 ml/min) than the contralateral healthy side (135 ml/min). Post-bypass this difference in pial flow between ipsilateral and contralateral sides decreased from 48 ml/min to 22 ml/min (p = 0.02). Collateral ratio decreased significantly (0.46 preoperatively vs. 0.18 postoperatively) (P &lt; 0.01). CONCLUSIONS: The results of this study quantitatively confirm that direct cerebral revascularization decreases collateral stress in patients with moyamoya disease.

The impact of collateral therapeutics on stroke hemodynamics in normotensive and hypertensive rats: a step toward translation.

Stroke interventions that increase collateral flow have the potential to salvage penumbral tissue and increase the number of patients eligible for reperfusion therapy. We compared the efficacy of two different collateral therapeutics during transient middle cerebral artery occlusion (tMCAO) in normotensive and hypertensive rats. The change in collateral and core perfusion was measured using dual laser Doppler in response to either a pressor agent (phenylephrine, 10 mg/kg iv or vehicle) or a collateral vasodilator (TM5441, 5 mg/kg iv or vehicle) given 30 min into tMCAO in male Wistar and spontaneously hypertensive rats (SHRs). Pressor therapy increased collateral flow in the Wistar rats but was ineffective in the SHRs. The increase in collateral flow in the Wistar rats was associated with impaired cerebral blood flow autoregulation (CBFAR) that was intact in the SHRs. TM5441 caused a decrease in collateral perfusion in the Wistar rats and a modest increase in the SHRs. The pressor therapy reduced early infarction in both groups but increased edema in the SHRs, whereas TM5441 did not have any beneficial effects in either group. Thus, the pressor therapy was superior to a collateral vasodilator in increasing collateral flow and improving outcomes in the Wistar rats, likely due to pial collaterals that were pressure passive; the lack of CBF response in the SHRs to pressor therapy was likely due to intact CBFAR that limited perfusion. While TM5441 modestly increased CBF in the SHRs but not in the Wistar rats, it did not have a beneficial effect on stroke outcomes. These results suggest that collateral therapies may need to be selected for certain comorbidities.

Impact of Cerebral Revascularization on Pial Collateral Flow in Patients With Unilateral Moyamoya Disease Using Quantitative Magnetic Resonance Angiography.

Moyamoya disease (MMD) is a chronic steno-occlusive disease of the intracranial circulation that depends on neoangiogenesis of collateral vessels to maintain cerebral perfusion and is primarily managed with cerebral revascularization surgery. A quantitative assessment of preoperative and postoperative collateral flow using quantitative magnetic resonance angiography with noninvasive optimal vessel analysis (NOVA) was used to illustrate the impact of revascularization on cerebral flow distribution. A retrospective review of patients with unilateral MMD who underwent direct, indirect, or combined direct/indirect cerebral revascularization surgery was conducted between 2011 and 2020. Using NOVA, flow was measured at the anterior cerebral artery (ACA), ACA distal to the anterior communicating artery (A2), middle cerebral artery (MCA), posterior cerebral artery (PCA), and PCA distal to the posterior communicating artery (P2). Pial flow (A2 + P2) and collateral flow (ipsilateral [A2 + P2])-(contralateral [A2 + P2]) were measured and compared before and after revascularization surgery. Total hemispheric flow (MCA + A2 + P2) with the addition of the bypass graft flow postoperatively was likewise measured. Thirty-four patients with unilateral MMD underwent cerebral revascularization. Median collateral flow significantly decreased from 68 to 39.5 mL/min ( P = .007) after bypass. Hemispheres with maintained measurable bypass signal on postoperative NOVA demonstrated significant reduction in median collateral flow after bypass ( P = .002). Median total hemispheric flow significantly increased from 227 mL/min to 247 mL/min ( P = .007) after bypass. Only one patient suffered an ipsilateral ischemic stroke, and no patients suffered a hemorrhage during follow-up. NOVA measurements demonstrate a reduction in pial collateral flow and an increase in total hemispheric flow after bypass for MMD, likely representing a decrease in leptomeningeal collateral stress on the distal ACA and PCA territories. Further studies with these measures in larger cohorts may elucidate a role for NOVA in predicting the risk of ischemic and hemorrhagic events in MMD.

Features of portal hemodynamics in patients with fatty liver disease: mechanisms of formation, clinical significance

There are few data in the literature on the state of portal and hepatic blood flow in patients with fatty liver disease, and portal hemodynamics at the pre-cirrhotic stage is practically not covered. The aim of the study was to study the features of portal hemodynamics in patients with fatty liver disease at the pre-cirrhotic stage. Materials and methods. The study included 43 patients (25 - patients with fatty liver disease and 18- a comparison group who applied to outpatient clinics of therapeutic profile aged 18-89 years (41.9% of men, 58.1% of women). The average age of the patients was 45.1± 19.4 years. Criteria for inclusion in the study: age 18 years and older; presence of fatty liver disease associated with metabolic conditions. Criteria for not being included in the study: the presence of viral hepatitis, alcoholic liver disease, autoimmune liver diseases, pregnancy, lactation, taking any medications, narcotic drugs, the presence of acute or exacerbation of chronic diseases. The anthropometric indicators of patients were evaluated: waist circumference (OT), body mass index (BMI), steatotic indices (St-index, Fatty Liver Index), liver fibrosis index (Fib 4). Portal hemodynamics was assessed using ultrasound Dopplerography on a Philips Affiniti 50 device. Sensor C5-1. The following criteria were evaluated: vessel diameter (mm), its cross-sectional area (PPP, cm2), time-averaged maximum velocity (TAMX, cm/s), time-averaged average blood flow velocity (TAV, cm/s), Doppler perfusion index was calculated using the formula: V vol SPA / V vol SPA + V vol BB), the stagnation index was calculated using the formula: PPP/TAV. The results obtained. In patients with fatty liver disease, structural and hemodynamic shifts in the portal blood flow system are recorded: an increase in the diameter of the portal and inferior vena cava, a larger cross-sectional area, a low time-averaged maximum blood flow velocity and time-averaged average blood flow velocity, an increase in the stagnation index for these vessels, which reflects the process of remodeling the liver as a target organ in fatty liver disease and its vascular bed, forming a “stagnant liver”. Patients have lower values of the time-averaged average blood flow rate through the splenic vein, which indicates the initiation of collateral blood flow. Portal hemodynamics indicators correlate with metabolic parameters (anthropometric characteristics of patients (OT, BMI), steatotic indices (St index, FLI), but not with the liver fibrosis index (Fib 4). These hemodynamic features at the pre-cirrhotic stage of the disease, correlating with the severity of metabolic disorders, exacerbate structural changes in the liver and necessitate their correction in patients with fatty liver disease.

Surgically induced aortic coarctation in a neonatal porcine model allows for longitudinal assessment of cardiovascular changes.

Noncritical aortic coarctation (COA) typically presents beyond early childhood with hypertension. Correction of COA does not ensure a return to normal cardiovascular health, but the mechanisms are poorly understood. Therefore, we developed a porcine COA model to study the secondary cardiovascular changes. Eight male neonatal piglets (4 sham, 4 COA) underwent left posterolateral thoracotomy with descending aorta (DAO) mobilization. COA was created via a 1-cm longitudinal DAO incision with suture closure, plication, and placement and an 8-mm external band. All animals had cardiac catheterization at 6 (11-13 kg), 12 (26-31 kg), and 20 (67-70 kg) wk of age. Aortic luminal diameters were similar along the thoracic aorta, except for the COA region [6.4 mm COA vs. 17.3 mm sham at 20 wk (P < 0.001)]. Collateral flow could be seen as early as 6 wk. COA peak systolic pressure gradient was 20 mmHg at 6 wk and persisted through 20 wk increasing to 40 mmHg with dobutamine. Pulse pressures distal to the COA were diminished at 12 and 20 wk. This model addresses many limitations of prior COA models including neonatal creation at an expected anatomic position with intimal injury and vessel sizes similar to humans.NEW & NOTEWORTHY A neonatal model of aortic coarctation was developed in a porcine model using a readily reproducible method of aortic plication and external wrap placement. This model addresses the limitations of existing models including neonatal stenosis creation, appropriate anatomic location of the stenosis, and intimal injury creation and mimics human somatic growth. Pigs met American Heart Association (AHA) criteria for consideration of intervention, and the stenoses were graded as moderate to severe.

Coil embolization of a giant pseudoaneurysm associated with a disrupted axillary artery: a case report

BackgroundStent-graft placement is generally used to treat pseudoaneurysm (PSA) of the axillary artery (AA) trunk to maintain the patency of peripheral vessels. Coil embolization of a PSA associated with a disrupted AA trunk has rarely been reported.Case presentationA 54-year-old woman presented with swelling of her right shoulder. She had had a right proximal humeral fracture 12 years earlier. Contrast-enhanced computed tomography (CECT) and subsequent angiograms revealed a giant PSA at the disrupted, distal right AA. There were collateral flows to the brachial artery from the proximal to the right AA. To preserve collateral flows to the brachial artery, selective embolization of the inflow artery that derived from the distal AA was performed with hydrogel-coated coils. The post-embolization arteriogram showed no flow into the PSA, but collateral flows to the brachial artery we preserved. The post-embolization course was uneventful. The patient regained warmth in her right arm and hand on post-embolization day 4. Repeat CECT on post-embolization day 9 confirmed blood-flow to her right radial artery.ConclusionsWhile a stent-graft should be used if the AA trunk can be preserved, coil embolization should be considered for PSA if the AA trunk is disrupted but collaterals are preserved.

The effect of an endovascular Heaney maneuver to achieve total hepatic isolation on survival, hemodynamic stability, retrohepatic bleeding, and collateral flow in a porcine model

PurposeCombining resuscitative endovascular balloon occlusion of the aorta (REBOA) and the inferior vena cava (REBOVC) with open surgery is a new hybrid approach for treating retrohepatic vena caval injuries. We compared endovascular total hepatic isolation with supraceliac REBOA ± suprahepatic REBOVC and no occlusion in experimental retrohepatic vena cava bleeding regarding survival, bleeding volume, hemodynamic stability, and arterial collateral blood flow.MethodsTwenty-five anesthetized pigs (n = 6–7/group) were randomized to REBOA; REBOA + REBOVC; REBOA + infra and suprahepatic REBOVC + portal vein occlusion (endovascular Heaney maneuver, four-balloon-occlusion, 4BO) or no occlusion. After balloon inflation, free bleeding was initiated from an open sheath in the retrohepatic vena cava. Bleeding volume, right internal thoracic artery (RITA) blood flow, hemodynamics, and arterial blood variables were measured until death or up to 90 min.ResultsThe REBOA group had a longer median survival time (63 min) compared with the 4BO (24 min, P = 0.02) and no occlusion (30 min, P = 0.02) groups, not versus the REBOA + REBOVC group (49 min, P > 0.05). The first 15 min accumulated bleeding was comparable in all groups (P > 0.05); Thereafter, bleeding volume was higher in the REBOA group versus the 4BO group (P < 0.05), not versus the other groups. RITA blood flow and MAP were higher in the REBOA group versus the other groups after 10 min of bleeding (P < 0.05).ConclusionsEndovascular Heaney maneuver was not beneficial for survival or hemodynamic stability in this porcine model, whereas supraceliac REBOA was. Anatomical differences in thoracoabdominal collaterals between pigs and humans must be considered when interpreting these results.

Melanocortin Derivatives Induced Vascularization and Neuroglial Proliferation in the Rat Brain under Conditions of Cerebral Ischemia.

Stroke remains the second leading cause of death worldwide. The development of new therapeutic agents focused on restoring vascular function and neuroprotection of viable tissues is required. In this study the neuroprotective activity of melanocortin-like ACTH(4-7)PGP and ACTH(6-9)PGP peptides was investigated in rat brain at 24 h after transient middle cerebral artery occlusion (tMCAO). The severity of ischemic damage, changes in the proliferative activity of neuroglial cells and vascularization of rat brain tissue were analyzed. The administration of peptides resulted in a significant increase in the volume density of neurons in the perifocal zone of infarction compared to rats subjected to ischemia and receiving saline. Immunohistochemical analysis of the proliferative activity of neuroglia cells using PCNA antibodies showed a significant increase in the number of proliferating cells in the penumbra and in the intact cerebral cortex of rats receiving peptide treatment. The effect of peptides on vascularization was examined using CD31 antibodies under tMCAO conditions, revealing a significant increase in the volume density of vessels and their sizes in the penumbra after administration of ACTH(4-7)PGP and ACTH(6-9)PGP. These findings confirm the neuroprotective effect of peptides due to the activation of neuroglia proliferation and the enhancement of collateral blood flow.

Collateral coronary flow in the interventricular septum detected on intracardiac echocardiographic imaging

Collateral coronary flow in the interventricular septum detected on intracardiac echocardiographic imaging

Has collateral blood flow any effect on restenosis rate? Our experience.

Restenosis is one of the important factors affecting the effectiveness of percutaneous transluminal angioplasty and stenting in the treatment of intracranial atherosclerotic stenosis. We aimed to clarify whether recruitable collateral flow could cause restenosis in patients treated with percutaneous transluminal angioplasty and stenting. Our study retrospectively analyzed patients with symptomatic severe intracranial atherosclerotic stenosis (≥70%) who underwent percutaneous transluminal angioplasty and stenting. We enrolled 28 patients with restenosis and 71 patients without restenosis. We analyzed baseline data, perioperative events, and follow-up results of patients in the two groups. Binary logistic regression analysis was used to identify restenosis predictors. For preoperative stroke, the restenosis group had a greater likelihood of having a previous stroke (89.3%), which was less prevalent in the non-restenosis group (66.2%) (P = 0.020). The restenosis group had a higher rate of re-stroke (21.4 vs. 4.2%, P = 0.022). After binary logistic regression analysis, collateral circulation and residual stenosis were independent risk factors of restenosis, with overall risk (95% confidence intervals) of 5.034 (1.484-4.066, P < 0.001) and 1.064 (1.006-1.125, P = 0.030), respectively. Restenosis risk increased 1.456-fold for each collateral circulation grade increase. However, for each 1% increase in residual stenosis, restenosis risk increased by 5.9% (P = 0.03). The chance of restenosis is minimal when the residual stenosis rate after percutaneous transluminal angioplasty and stent implantation is 15.85%. Good collateral circulation was significantly associated with restenosis in patients undergoing intracranial angioplasty, the residual stenosis rate tends to be 15.85% to reduce restenosis risk. Compared to patients with restenosis, those without restenosis have a low stroke risk during follow-up.

Impact of coronary hyperemia on collateral flow correction of coronary microvascular resistance indices.

Recently, a novel method to estimate wedge pressure (Pw)-corrected minimal microvascular resistance (MR) was introduced. However, this method has not been validated since, and there are some theoretical concerns regarding the impact of different physiological conditions on the derivation of Pw measurements. This study sought to validate the recently introduced method to estimate Pw-corrected MR in a Doppler-derived study population and to evaluate the impact of different physiological conditions on the Pw measurements and the derivation of Pw-corrected MR. The method to derive "estimated" hyperemic microvascular resistance (HMR) without the need for Pw measurements was validated by estimating the coronary fractional flow reserve (FFRcor) from myocardial fractional flow reserve (FFRmyo) in a Doppler-derived study population (N = 53). From these patients, 24 had hyperemic Pw measurements available for the evaluation of hyperemic conditions on the derivation of Pw and its effect on the derivation of both "true" (with measured Pw) and "estimated" Pw-corrected HMR. Nonhyperemic Pw differed significantly from Pw measured in hyperemic conditions (26 ± 14 vs. 35 ± 14 mmHg, respectively, P < 0.005). Nevertheless, there was a strong linear relationship between FFRcor and FFRmyo in nonhyperemic conditions (R2 = 0.91, P < 0.005), as well as in hyperemic conditions (R2 = 0.87, P < 0.005). There was a strong linear relationship between "true" HMR and "estimated" HMR using either nonhyperemic (R2 = 0.86, P < 0.005) or hyperemic conditions (R2 = 0.85, P < 0.005) for correction. In contrast to a modest agreement between nonhyperemic Pw-corrected HMR and apparent HMR (R2 = 0.67, P < 0.005), hyperemic Pw-corrected HMR showed a strong agreement with apparent HMR (R2 = 0.88, P < 0.005). We validated the calculation method for Pw-corrected MR in a Doppler velocity-derived population. In addition, we found a significant impact of hyperemic conditions on the measurement of Pw and the derivation of Pw-corrected HMR.NEW & NOTEWORTHY The following are what is known: 1) wedge-pressure correction is often considered for the derivation of indices of minimal microvascular resistance, and 2) the Yong method for calculating wedge pressure-corrected index of microvascular resistance (IMR) without balloon inflation has never been validated in a Doppler-derived population and has not been tested under different physiological conditions. This study 1) adds validation for the Yong method for calculated wedge-pressure correction in a Doppler-derived study population and 2) shows significant influence of the physiological conditions on the derivation of coronary wedge pressure.

Systemic-to-pulmonary collateral flow associations with antegrade pulmonary flow in single ventricle patients: insights from cardiac magnetic resonance imaging.

In the palliated single ventricle anomalies, a considerable amount of the aortic flow may be absorbed by the systemic-pulmonary collateral flow (SPCF), which can be noninvasively assessed by cardiac magnetic resonance (CMR). The aims of this study were to (1) identify factors associated with SCPF in pediatric single ventricle patients, and (2) establish a cutoff values indicating an association between SCPF and a reduction in antegrade pulmonary flow. A retrospective single-tertiary-center cohort study included 158 consecutive CMR studies of patients with a single ventricle. In the uni- and multivariable analysis, SPCF was presented as a percentage of the total pulmonary venous flow (SPCF%PV). The minimal clinically important difference in QP/QS ratios was estimated as ≥0.50, and an optimal cutoff value was defined using the receiver operating characteristic (ROC) curve. SPCF%PV was significantly smaller in the post-total cavopulmonary connection (TCPC) group than in the pre-TCPC patients (p < 0.001). The patient's higher age and a higher antegrade pulmonary flow were associated with a lower SPCF%PV. A negative weak association was observed between the SPCF%PV and systemic saturation (r = -0.39, p < 0.001). SPCF%PV did not associate with ventricular volumes nor ejection fraction. The SPCF%PV was significantly smaller in patients that were palliated primarily with a pulmonary artery banding compared to those palliated with a BT-shunt (p = 0.002) or RV-PA- shunt (p = 0.044). In the ROC analysis, for pre-TCPC patient's, a cutoff of SPCF%PV 42% yielded a sensitivity of 100% and specificity of 80% for significantly reduced antegrade pulmonary flow (AUC 0.97). In the post-TCPC group, the optimal SPCF%PV cutoff was 34% (sensitivity 100%, specificity 98%, AUC 0.99). SPCF results in a considerable left-to-right shunt, which subsequently diminishes spontaneously after TCPC. Our findings indicated that for pre-TCPC patients, an SPCF%PV threshold of 42% (sensitivity 100%, specificity 80%), and for the post-TCPC group, a threshold of 34% (sensitivity 100%, specificity 98%) were effective in identifying reduced antegrade pulmonary flow.

Microsurgical Techniques for Digital Nerve Injuries and Vascular Injuries.

Tension-free end-to-end digital nerve repair or reconstruction under loupe or microscope magnification are surgical treatment options for lacerated digital nerves in patients with multiple injured digits, injuries to the border digits, or injuries to the thumb, with the goal of improved or restored sensation and a decreased risk of painful traumatic neuroma formation. Different techniques for primary repair have been described and include epineurial sutures, nerve "glues" including fibrin-based gels1,2, biologic or synthetic absorbable or nonabsorbable nerve wraps or conduits, or a combination of these materials. Nerve "glues" have demonstrated decreased initial gapping at the repair site3 and an increased tensile load to failure when utilized with a nerve wrap or conduit4,5. When there is a gap or defect in the nerve and primary repair is not feasible, nerve allograft and autograft provide similar results and are both better options than conduit reconstruction6. Concomitant or isolated digital vascular injuries may also be surgically treated with end-to-end repair in a dysvascular digit, with the goal of digit and function preservation. In the absence of complete circumferential injury or complete amputation, redundant or collateral flow may be present. Single digital artery injuries often do not need to be repaired because of the collateral flow from the other digital artery. Digital nerve and vascular injuries are often found in the context of traumatic wounds. In such cases, surgical exploration is often required, with possible surgical extension of the wounds to facilitate identification of the neurovascular bundles. The proximal and distal ends of the transected nerve and/or artery are identified, and the traumatized ends are incised sharply, maintaining as much length as possible to facilitate end-to-end repair, interposition of a graft, and the use of a conduit. The proximal and distal aspects of the nerve and/or artery are appropriately mobilized by dissecting or releasing any scar tissue or soft tissue that may be tethering the structure. The defect is measured in the natural resting position of the digit. Gentle flexion of the digit may be performed to facilitate a primary repair in the setting of very small defects. Primary repair or reconstruction is selected, and an 8-0 or 9-0 nonabsorbable monofilament suture is utilized to anastomose the appropriate structures under magnification with use of a single or double stitch6. A tubular nerve conduit is placed prior to epineurial suturing, or a nerve conduit wrap is applied circumferentially around the repair site and augmented with a fibrin glue. The wound is then irrigated and closed in a standard fashion, as determined by the presence of any soft-tissue or structural injury. Alternatives to primary repair include the use of conduits or autologous or allogenic grafting. Factors that necessitate reconstruction include gapping and poor soft-tissue integrity, which can be related to the mechanism of injury. Alternatives to repair or reconstruction include treatment of the-soft tissue or structural injury without concomitant repair or reconstruction of the damaged digital nerves or vessels. Primary end-to-end repair and reconstruction of digital nerves increases a patient's likelihood of sensation recovery, and arterial repair can preserve a digit and avoid the need for amputation. Sensation in the digits is very important for fine motor skills and interaction with the environment, and it is particularly important for patients who rely on their hands for work and/or recreation. For these reasons, the digital nerves to the border digits, such as the ulnar aspect of the small finger, radial aspect of the index finger, and both digital nerves to the thumb, are given particular attention. Surgical intervention to repair or reconstruct the digital nerves increases the likelihood of recovering pre-injury sensation; however, the chance of complete recovery remains low. A systematic review of the outcomes of digital nerve repair in adults published in 2019 showed that the average percentage of patients who had undergone repair and reported a recovery to Highet grade 4 was 24% (range, 6% to 60%)8. The rate of adverse events was comparable between the operatively and nonoperatively treated patients, with complications including neuromas, hyperesthesia, and infection. The use of a microvascular background material can provide better visualization of the proximal and distal ends while performing the repair.It is important to sharply guillotine the ends of the nerve to freshen up the laceration and provide healthy nerve ends for repair.Repair sutures need to be passed through the epineurium, with care taken not to pass through the nerve fascicles. OR = operating roomPIP = proximal interphalangealPT = prothrombin timePTT = partial thromboplastin time.

Abstract WP303: Hypertension Disrupts the Relationship Between Pial Collateral Flow and Tissue Oxygenation During Ischemic Stroke

Introduction: Chronic hypertension decreases collateral blood flow through leptomeningeal anastomoses (LMAs) during ischemic stroke, which has been linked to worsened stroke outcome. Given the important relationship between LMA flow, tissue oxygenation and cortical cerebral blood flow (CBF), we characterized the interplay between CBF and tissue oxygenation during the sub-acute progression of ischemia in normotensive Wistar (n=6) and spontaneously hypertensive rats (SHR, n=5). Methods: Transient middle cerebral artery occlusion was used to induce ischemia for 2 hours. Relative change in LMA flow, normalized to initial drop after occlusion, was measured via surface laser Doppler; tissue oxygenation and change in parenchymal CBF were measured using a combined laser Doppler-oxygen sensor placed in the expected cortical peri-infarct region. Recording was done at 400Hz, and data analyzed in 20 second blocks over the first hour of ischemia. Data reported as mean ± SEM, statistical comparisons done via Mann-Whitney tests. Results: CBF through LMAs was significantly higher in Wistars compared to SHR at 60 min of occlusion (156±18% vs 80±4% p&lt;0.05). Pial LMA flow strongly correlated with tissue CBF (Wistar: r=0.91, SHR: r=0.75), which was also greater in Wistars at 60 min compared to SHR (80±14% vs.19±3%, p&lt;0.05). Tissue oxygenation initially dropped below 10mmHg in all animals, increasing in Wistars over the course of ischemia to 22.8±0.34 mmHg at 60 min. However, oxygenation did not recover in SHR (5.9±0.23 mmHg). The relationship between CBF and oxygenation was strongly correlated in Wistar rats with both LMA (r=0.88) and tissue CBF (r=0.88). However, in SHR, oxygenation had an inverse relationship with CBF (LMA: r= - 0.56, tissue CBF r= - 0.37). Conclusion: Under normotensive conditions the relationship between CBF and oxygenation had a strong, linear relationship. However, this relationship was disrupted by chronic hypertension, with LMA and tissue CBF increasing without an increase in tissue oxygenation. This uncoupling was potentially due to cerebrovascular dysfunction and metabolic dysregulation due to chronic hypertension. These findings could be an important consideration for the development of stroke therapeutics in hypertensive patients.

Abstract TP199: Prominent Laterality of the Posterior Cerebral Artery on MR Angiography Before Mechanical Thrombectomy in Patients With the Middle Cerebral Artery Occlusion Predicts Long-Term Functional Outcome

Background and Purpose: Well-developed collateral flow is reported to be associated with a reduction of infarct volume, successful reperfusion, and better functional outcome in acute ischemic stroke (AIS). Relatively increased visualization of posterior cerebral artery (PCA) ipsilateral to the ischemic lesion on MR angiography (MRA), a sign of prominent PCA laterality (PCAL), represents the development of collateral flow from PCA to middle cerebral artery (MCA) territory. However, the prognostic value of PCAL on functional outcome in AIS patients having MCA occlusion and undergoing mechanical thrombectomy, is not well known. Methods: We retrospectively reviewed initial MRA scans of pre-morbidly independent patients treated with mechanical thrombectomy for M1-segment occlusion from September 2017 to May 2022. PCAL was defined as better visualization of ipsilateral PCA, compared to contralateral PCA, by one or more segments on MRA. We divided patients into two groups, those presenting PCAL and not, and compared the background characteristics, in-hospital management, and functional outcome between the two groups. Factors associated with favorable outcome (mRS score 0-2) at 3 months after onset were assessed using multivariate logistic regression analysis. Results: In total, 172 patients (76 female [44%], median age 77 [IQR 74.5-78.0] years, median NIHSS score 16 [15-18]) were included. Of these, 86 patients (50%) presented PCAL on initial MRA. There is no significant difference between the two groups in age, sex, major vascular risk factors, NIHSS on admission, DWI-ASPECTS, onset-to-recanalization time (OTR), and preclinical modified Rankin scale. Multivariate logistic regression analysis showed an adjusted odds ratio of 2.11 for a favorable outcome in patients with PCAL (95% CI: 0.986 to 4.53, P=0.054). When focused on the cases with OTR &gt;6 hours (n=53), PCAL was independently associated with favorable outcome (OR 5.77, 95% CI: 1.28 to 26.0, P=0.022). Conclusion: PCAL on initial MRA in patients with M1-segment occlusion predicts favorable long-term functional outcome after mechanical thrombectomy, especially in the case taking longer time from onset to recanalization.

Competitive leptomeningeal flow impact on thrombectomy reperfusion grade rating

BackgroundCompetitive leptomeningeal flow (CLF) can be observed immediately after mechanical thrombectomy (MT) reperfusion with retrograde contrast clearing of the distal leptomeningeal branches from non-contrast opacified flow through different vascular territories....

Abstract WP141: Leptomeningeal Competitive Flow Impact on Thrombectomy Reperfusion Grade Rating

Background: The extent of reperfusion following thrombectomy (MT) for large vessel occlusion strokes is predictive of outcomes. There is still inter-rater variability in the reperfusion scoring. We noticed that some patients present with retrograde contrast clearing of the distal branches from non-contrast-opacified flow originated from different territories. We aim to evaluate the frequency of this phenomenon (“competitive flow” (CF)), to evaluate if it has an association with the degree of leptomeningeal collaterals, and its impact on eTICI score. Methods: This is a retrospective-analysis of our MT database spanning 11/2020-12/2021. We included consecutive cases of intracranial internal carotid (i-ICA) and middle cerebral artery (MCA) M1 occlusions. CF was defined by the observation of retrograde clearing of distal MCA branches that were previously opacified by antegrade reperfusion. The clearance of the distal branches is presumed to occur due to CF via non-contrast-opacified PCA or ACA flow. The washout was considered CF if it cleared abruptly with or without forward reconstitution of antegrade opacification. Results: We included a 125 patients. Median age was 64years, 51%were males. Baseline median NIHSS was 17 and ASPECTS 9. Median last-known-well-time to puncture was 7 hours, 30.4% received tPA. Final eTICI2c-3 was achieved in 81.6%. CF was present in 32(25.6%)patients. Baseline characteristics were similar between both groups. The CF arm had better leptomeningeal single-phase-CTA-collaterals(p=0.01) and smaller CTP malignant hypoperfusion volume(p=0.06) VS non-CF. The inter-rater-agreement for eTICI score was moderate when CF was present and excellent in its absence (Krippendorf’s alpha=0.65 and 0.81,respectively). There was poor agreement (K-value=0.3) for the presence versus absence of CF between both operators. Reviewer 1 (2-year-post-training) had correctly identified 46% of patients with consensus CF vs 90% to Reviewer 2 (9-year-post-training) after the consensus read. Conclusion: CF was observed in 32% of patients. CF was found to be associated with better collateral flow, and to impact the reported procedural eTICI rating.