Asymptomatic high flow subclavian steal in a patient with hemodialysis access.

Subclavian steal phenomenon due to proximal subclavian artery stenosis or occlusion is not un-common but often remains asymptomatic. We describe the case of a 66-year-old man with end-stage renal disease hemodialysed through a brachio-brachial loop graft of the left forearm. Echo-Doppler precerebral examination showed a high reversed flow of 570 ml/min in the ipsilateral vertebral artery. After successful endovascular recanalization of the subclavian artery, access blood flow increased and vertebral flow decreased to 30 ml/min. Complete neurological examination was normal both before and after endovascular treatment. This case demonstrates how high a subclavian steal can be without causing symptoms and how well precerbral and cerebral circulation can adapt to hemodynamic changes.

Transcranial Doppler for predicting delayed cerebral ischemia after subarachnoid hemorrhage.

OBJECTIVE: Transcranial Doppler (TCD) is widely used to monitor the temporal course of vasospasm after subarachnoid hemorrhage (SAH), but its ability to predict clinical deterioration or infarction from delayed cerebral ischemia (DCI) remains controversial. We sought to determine the prognostic utility of serial TCD examination after SAH. METHODS: We analyzed 1877 TCD examinations in 441 aneurysmal SAH patients within 14 days of onset. The highest mean blood flow velocity (mBFV) value in any vessel before DCI onset was recorded. DCI was defined as clinical deterioration or computed tomographic evidence of infarction caused by vasospasm, with adjudication by consensus of the study team. Logistic regression was used to calculate adjusted odds ratios for DCI risk after controlling for other risk factors. RESULTS: DCI occurred in 21% of patients (n = 92). Multivariate predictors of DCI included modified Fisher computed tomographic score (P = 0.001), poor clinical grade (P = 0.04), and female sex (P = 0.008). After controlling for these variables, all TCD mBFV thresholds between 120 and 180 cm/s added a modest degree of incremental predictive value for DCI at nearly all time points, with maximal sensitivity by SAH day 8. However, the sensitivity of any mBFV more than 120 cm/s for subsequent DCI was only 63%, with a positive predictive value of 22% among patients with Hunt and Hess grades I to III and 36% in patients with Hunt and Hess grades IV and V. Positive predictive value was only slightly higher if mBFV exceeded 180 cm/s. CONCLUSION: Increased TCD flow velocities imply only a mild incremental risk of DCI after SAH, with maximal sensitivity by day 8. Nearly 40% of patients with DCI never attained an mBFV more than 120 cm/s during the course of monitoring. Given the poor overall sensitivity of TCD, improved methods for identifying patients at high risk for DCI after SAH are needed.

PulseCath iVAC 3LTM hemodynamic performance for simple assisted flow.

The PulseCath iVAC 3L? left ventricular assist device is an option to treat transitory left heart failure or dysfunction post-cardiac surgery. Assisted blood flow should reach up to 3 l/min. In the present in vitro model exact pump flow, depending on various frequencies and afterload was examined. Optimal flow was achieved with inflation/deflation frequencies of about 70-80/min. The maximal flow rate was achieved at about 2.5 l/min with a minimal afterload of 22 mmHg. Handling of the device was easy due to the connection to a standard intra-aortic balloon pump console. With increasing afterload (up to a simulated mean systemic pressure of 66 mmHg) flow rate and cardiac support are in some extent limited.

High-resolution spatial mapping of changes in the neurochemical profile after focal ischemia in mice.

After ischemic stroke, the ischemic damage to brain tissue evolves over time and with an uneven spatial distribution. Early irreversible changes occur in the ischemic core, whereas, in the penumbra, which receives more collateral blood flow, the damage is more mild and delayed. A better characterization of the penumbra, irreversibly damaged and healthy tissues is needed to understand the mechanisms involved in tissue death. MRSI is a powerful tool for this task if the scan time can be decreased whilst maintaining high sensitivity. Therefore, we made improvements to a (1) H MRSI protocol to study middle cerebral artery occlusion in mice. The spatial distribution of changes in the neurochemical profile was investigated, with an effective spatial resolution of 1.4 μL, applying the protocol on a 14.1-T magnet. The acquired maps included the difficult-to-separate glutamate and glutamine resonances and, to our knowledge, the first mapping of metabolites γ-aminobutyric acid and glutathione in vivo, within a metabolite measurement time of 45 min. The maps were in excellent agreement with findings from single-voxel spectroscopy and offer spatial information at a scan time acceptable for most animal models. The metabolites measured differed with respect to the temporal evolution of their concentrations and the localization of these changes. Specifically, lactate and N-acetylaspartate concentration changes largely overlapped with the T(2) -hyperintense region visualized with MRI, whereas changes in cholines and glutathione affected the entire middle cerebral artery territory. Glutamine maps showed elevated levels in the ischemic striatum until 8 h after reperfusion, and until 24 h in cortical tissue, indicating differences in excitotoxic effects and secondary energy failure in these tissue types. Copyright © 2011 John Wiley & Sons, Ltd.

Red blood cell microparticles: clinical relevance.

Microparticles are small phospholipid vesicles of less than 1 µm released into the blood flow by various types of cells such as endothelial, platelet, white or red blood cells. They are involved in many biological and physiological processes including hemostasis. In addition, an elevated number of microparticles in the blood is observed in various pathological situations. In the context of transfusion, erythrocyte-derived microparticles are found in red blood cell concentrates. Their role is not elucidated, and they are considered as a type of storage lesion. The purpose of this review is to present recent data showing that erythrocyte-derived microparticles most likely play a role in transfusion medicine and could cause transfusion complications.

Coronary vasomotor control in obesity and morbid obesity: contrasting flow responses with endocannabinoids, leptin, and inflammation.

OBJECTIVES: This study sought to investigate abnormalities in coronary circulatory function in 2 different disease entities of obese (OB) and morbidly obese (MOB) individuals and to evaluate whether these would differ in severity with different profiles of endocannabinoids, leptin, and C-reactive protein (CRP) plasma levels. BACKGROUND: There is increasing evidence that altered plasma levels of endocannabinoids, leptin, and CRP may affect coronary circulatory function in OB and MOB. METHODS: Myocardial blood flow (MBF) responses to cold pressor test from rest and during pharmacologically induced hyperemia were measured with N-13 ammonia positron emission tomography/computed tomography. Study participants (n = 111) were divided into 4 groups based on their body mass index (BMI) (kg/m(2)): 1) control group (BMI: 20 to 24.9, n = 30); 2) overweight group (BMI: 25 to 29.9, n = 31), 3) OB group (BMI: 30 to 39.9, n = 25); and 4) MOB group (BMI ≥40, n = 25). RESULTS: The cold pressor test-induced change in endothelium-related MBF response (ΔMBF) progressively declined in overweight and OB groups when compared with the control group [median: 0.19 (interquartile range [IQR] 0.08, 0.27) and 0.11 (0.03, 0.17) vs. 0.27 (0.23, 0.38) ml/g/min; p ≤ 0.01, respectively], whereas it did not differ significantly between OB and MOB groups [median: 0.11 (IQR: 0.03, 0.17) and 0.09 (-0.01, 0.19) ml/g/min; p = 0.93]. Compared with control subjects, hyperemic MBF subjects comparably declined in the overweight, OB, and MOB groups [median: 2.40 (IQR 1.92, 2.63) vs. 1.94 (1.65, 2.30), 2.05 (1.67, 2.38), and 2.14 (1.78, 2.76) ml/g/min; p ≤ 0.05, respectively]. In OB individuals, ΔMBF was inversely correlated with increase in endocannabinoid anandamide (r = -0.45, p = 0.044), but not with leptin (r = -0.02, p = 0.946) or with CRP (r = -0.33, p = 0.168). Conversely, there was a significant and positive correlation among ΔMBF and elevated leptin (r = 0.43, p = 0.031) and CRP (r = 0.55, p = 0.006), respectively, in MOB individuals that was not observed for endocannabinoid anandamide (r = 0.07, p = 0.740). CONCLUSIONS: Contrasting associations of altered coronary endothelial function with increases in endocannabinoid anandamide, leptin, and CRP plasma levels identify and characterize OB and MOB as different disease entities affecting coronary circulatory function.

Total aortic arch stenting--hemodynamical impact of carotid artery perfusion.

The aim of this experimental study is to evaluate the feasibility and the outcome of total endovascular stent implantation in the aortic arch. Indications for this operation-technique would be acute or chronic dissection of the aortic arch (non-A-non-B dissection) or type B dissection with retrograde extension. Four pigs were canulated via the distal abdominal aorta and a retrograde placement of a Djumbodis arch stent (4-9 cm) was controlled by using intravascular ultrasound and intracardiac ultrasound by the inferior cava vein and under radioscopic control. Cerebral perfusion, by using a flow meter placed on one prepared carotid artery, were controlled before, immediate post-procedural (<1 min), and in the early follow-up after aortic arch stent implantation. During the implantation process, especially during balloon inflation and deflation, mean carotid perfusion decreases slightly. A reactive increase of carotid perfusion after stent placements indicates transitory cerebral hypo-perfusion. Non-covered aortic arch stent implantation is technically feasible and could be a potential treatment option in otherwise inoperable arch dissections. The time required for balloon inflation and deflation causes an important risk of cerebral ischemia. The latter can be reduced by transaxillary perfusion.

Structural alterations of the coronary arterial wall are associated with myocardial flow heterogeneity in type 2 diabetes mellitus.

PURPOSE: To determine the relationship between carotid intima-media thickness (IMT), coronary artery calcification (CAC), and myocardial blood flow (MBF) at rest and during vasomotor stress in type 2 diabetes mellitus (DM). METHODS: In 68 individuals, carotid IMT was measured using high-resolution vascular ultrasound, while the presence of CAC was determined with electron beam tomography (EBT). Global and regional MBF was determined in milliliters per gram per minute with (13)N-ammonia and positron emission tomography (PET) at rest, during cold pressor testing (CPT), and during adenosine (ADO) stimulation. RESULTS: There was neither a relationship between carotid IMT and CAC (r = 0.10, p = 0.32) nor between carotid IMT and coronary circulatory function in response to CPT and during ADO (r = -0.18, p = 0.25 and r = 0.10, p = 0.54, respectively). In 33 individuals, EBT detected CAC with a mean Agatston-derived calcium score of 44 +/- 18. There was a significant difference in regional MBFs between territories with and without CAC at rest and during ADO-stimulated hyperemia (0.69 +/- 0.24 vs. 0.74 +/- 0.23 and 1.82 +/- 0.50 vs. 1.95 +/- 0.51 ml/g/min; p < or = 0.05, respectively) and also during CPT in DM but less pronounced (0.81 +/- 0.24 vs. 0.83 +/- 0.23 ml/g/min; p = ns). The increase in CAC was paralleled with a progressive regional decrease in resting as well as in CPT- and ADO-related MBFs (r = -0.36, p < or = 0.014; r = -0.46, p < or = 0.007; and r = -0.33, p < or = 0.041, respectively). CONCLUSIONS: The absence of any correlation between carotid IMT and coronary circulatory function in type 2 DM suggests different features and stages of early atherosclerosis in the peripheral and coronary circulation. PET-measured MBF heterogeneity at rest and during vasomotor stress may reflect downstream fluid dynamic effects of coronary artery disease (CAD)-related early structural alterations of the arterial wall.

Phase-sensitive black-blood coronary vessel wall imaging.

Black-blood MR coronary vessel wall imaging may become a powerful tool for the quantitative and noninvasive assessment of atherosclerosis and positive arterial remodeling. Although dual-inversion recovery is currently the gold standard, optimal lumen-to-vessel wall contrast is sometimes difficult to obtain, and the time window available for imaging is limited due to competing requirements between blood signal nulling time and period of minimal myocardial motion. Further, atherosclerosis is a spatially heterogeneous disease, and imaging at multiple anatomic levels of the coronary circulation is mandatory. However, this requirement of enhanced volumetric coverage comes at the expense of scanning time. Phase-sensitive inversion recovery has shown to be very valuable for enhancing tissue-tissue contrast and for making inversion recovery imaging less sensitive to tissue signal nulling time. This work enables multislice black-blood coronary vessel wall imaging in a single breath hold by extending phase-sensitive inversion recovery to phase-sensitive dual-inversion recovery, by combining it with spiral imaging and yet relaxing constraints related to blood signal nulling time and period of minimal myocardial motion.

A case of dissection of intracranial cerebral arteries with segmental mediolytic "arteritis".

The intravital diagnosis of intracranial arterial dissection is not always possible due to atypic and non-specific clinical and radiological presentations. The postmortem pathological examination of cerebral blood vessels is therefore necessary to establish or confirm the presence of a dissecting aneurysm of intracranial arteries. Most of the described cases showed no significant underlying vascular pathology. Here we present the case of a 24-year-old women who died 5 days after admission to the hospital for a rapidly developing right-sided hemisyndrome. Neuroradiological examination had revealed ill-defined bifrontal hypodense lesions and angiographic findings were compatible with a dissection of the left extracranial internal carotid artery with embolic subocclusion of both anterior cerebral arteries. The pathological evaluation ruled out a thromboembolic occlusion of cerebral arteries and an extracranial internal carotid artery dissection but showed an extended dissecting process of variable age in the anterior circulation of the circle of Willis. The dissected vessels showed pathological changes characteristic of segmental mediolytic "arteritis" [Slavin and Gonzalez-Vitale 1976]. To our knowledge this is the first report on intracranial arteries being affected by this pathologic entity. Our case illustrates the importance of a postmortem examination of dissecting aneurysms of intracranial arteries. Careful serial section studies of dissected intracranial arteries in young subjects should be performed and may allow for a better understanding of the vascular pathology underlying the dissection processus.

Telomere length dynamics in human lymphocyte subpopulations measured by flow cytometry.

To measure the average length of telomere repeats at chromosome ends in individual cells we developed a flow cytometry method using fluorescence in situ hybridization (flow FISH) with labeled peptide nucleic acid (PNA) probes. Results of flow FISH measurements correlated with results of conventional telomere length measurements by Southern blot analysis (R = 0.9). Consistent differences in telomere length in CD8+ T-cell subsets were identified. Naive and memory CD4+ T lymphocytes in normal adults differed by around 2.5 kb in telomere length, in agreement with known replicative shortening of telomeres in lymphocytes in vivo. T-cell clones grown in vitro showed stabilization of telomere length after an initial decline and rare clones capable of growing beyond 100 population doublings showed variable telomere length. These results show that flow FISH can be used to measure specific nucleotide repeat sequences in single cells and indicate that the very large replicative potential of lymphocytes is only indirectly related to telomere length.

Right coronary artery flow velocity and volume assessment with spiral K-space sampled breathhold velocity-encoded MRI at 3 tesla: accuracy and reproducibility.

PURPOSE: To evaluate accuracy and reproducibility of flow velocity and volume measurements in a phantom and in human coronary arteries using breathhold velocity-encoded (VE) MRI with spiral k-space sampling at 3 Tesla. MATERIALS AND METHODS: Flow velocity assessment was performed using VE MRI with spiral k-space sampling. Accuracy of VE MRI was tested in vitro at five constant flow rates. Reproducibility was investigated in 19 healthy subjects (mean age 25.4 +/- 1.2 years, 11 men) by repeated acquisition in the right coronary artery (RCA). RESULTS: MRI-measured flow rates correlated strongly with volumetric collection (Pearson correlation r = 0.99; P < 0.01). Due to limited sample resolution, VE MRI overestimated the flow rate by 47% on average when nonconstricted region-of-interest segmentation was used. Using constricted region-of-interest segmentation with lumen size equal to ground-truth luminal size, less than 13% error in flow rate was found. In vivo RCA flow velocity assessment was successful in 82% of the applied studies. High interscan, intra- and inter-observer agreement was found for almost all indices describing coronary flow velocity. Reproducibility for repeated acquisitions varied by less than 16% for peak velocity values and by less than 24% for flow volumes. CONCLUSION: 3T breathhold VE MRI with spiral k-space sampling enables accurate and reproducible assessment of RCA flow velocity.

The effects of arterial flow on platelet activation, thrombus growth, and stabilization.

Injury of an arterial vessel wall acutely triggers a multifaceted process of thrombus formation, which is dictated by the high-shear flow conditions in the artery. In this overview, we describe how the classical concept of arterial thrombus formation and vascular occlusion, driven by platelet activation and fibrin formation, can be extended and fine-tuned. This has become possible because of recent insight into the mechanisms of: (i) platelet-vessel wall and platelet-platelet communication, (ii) autocrine platelet activation, and (iii) platelet-coagulation interactions, in relation to blood flow dynamics. We list over 40 studies with genetically modified mice showing a role of platelet and plasma proteins in the control of thrombus stability after vascular injury. These include multiple platelet adhesive receptors and other junctional molecules, components of the ADP receptor signalling cascade to integrin activation, proteins controlling platelet shape, and autocrine activation processes, as well as multiple plasma proteins binding to platelets and proteins of the intrinsic coagulation cascade. Regulatory roles herein of the endothelium and other blood cells are recapitulated as well. Patient studies support the contribution of platelet- and coagulation activation in the regulation of thrombus stability. Analysis of the factors determining flow-dependent thrombus stabilization and embolus formation in mice will help to understand the regulation of this process in human arterial disease.

Myocardial flow reserve by Rb-82 cardiac PET improves the selection of patients eligible for invasive coronary angiography

Aim: We asked whether myocardial flow reserve (MFR) by Rb-82 cardiac PET improve the selection of patients eligible for invasive coronary angiography (ICA). Material and Methods: We enrolled 26 consecutive patients with suspected or known coronary artery disease who performed dynamic Rb-82 PET/CT and (ICA) within 60 days; 4 patients who underwent revascularization or had any cardiovascular events between PET and ICA were excluded. Myocardial blood flow at rest (rMBF), at stress with adenosine (sMBF) and myocardial flow reserve (MFR=sMBF/rMBF) were estimated using the 1-compartment Lortie model (FlowQuant) for each coronary arteries territories. Stenosis severity was assessed using computer-based automated edge detection (QCA). MFR was divided in 3 groups: G1:MFR<1.5, G2:1.5≤MFR<2 and G3:2≤MFR. Stenosis severity was graded as non-significant (<50% or FFR ≥0.8), intermediate (50%≤stenosis<70%) and severe (≥70%). Correlation between MFR and percentage of stenosis were assessed using a non-parametric Spearman test. Results: In G1 (44 vessels), 17 vessels (39%) had a severe stenosis, 11 (25%) an intermediate one, and 16 (36%) no significant stenosis. In G2 (13 vessels), 2 (15%) vessels presented a severe stenosis, 7 (54%) an intermediate one, and 4 (31%) no significant stenosis. In G3 (9 vessels), 0 vessel presented a severe stenosis, 1 (11%) an intermediate one, and 8 (89%) no significant stenosis. Of note, among 11 patients with 3-vessel low MFR<1.5 (G1), 9/11 (82%) had at least one severe stenosis and 2/11 (18%) had at least one intermediate stenosis. There was a significant inverse correlation between stenosis severity and MFR among all 66 territories analyzed (rho= -0.38, p=0.002). Conclusion: Patients with MFR>2 could avoid ICA. Low MFR (G1, G2) on a vessel-based analysis seems to be a poor predictor of severe stenosis severity. Patients with 3-vessel low MFR would benefit from ICA as they are likely to present a significant stenosis in at least one vessel.

Effets de la perfusion de facteurs natriurétiques auriculaires synthétiques sur quelques flux régionaux chez le volontaire sain [Effect of synthetic atrial natriuretic factors on various regional blood flows in the healthy subject]

The effects of continuous infusions of 2 synthetic atrial natriuretic peptides Ile12-(3-28) (rANP) and Meth12-(3-28) (hANP) eicosahexapeptides on blood pressure, heart rate, skin blood flow, glomerular filtration rate, renal plasma flow, apparent hepatic blood flow, and carotid blood flow were evaluated in normal volunteers. A rANP infusion at increasing rates (1-40 micrograms/min) induced a decrease in blood pressure, an increase in heart rate and in skin blood flow linearly related to the dose administered. In contrast, hANP infusion at 1 microgram/min for 4 hours induced an initial increase followed by a secondary fall in skin blood flow without blood pressure changes. A 4-hour rANP infusion at 0.5 and 5 mcg/min did not alter glomerular filtration rate but induced a delayed and dose-related fall in renal plasma flow from 531 to 461 (p less than 0.05), and from 554 to 342 ml/min (p less than 0.001) respectively, with a consequential rise in the filtration fraction. The 5 mcg/min dose furthermore significantly reduced blood pressure following a latency period of 2.5 hours. A 2-hours rANP infusion at 0.5 micrograms/min induced a fall in apparent hepatic blood flow from 1,087 to 863 ml/min (p less than 0.01), without simultaneously altering blood pressure. Similarly, a 2-hour hANP infusion at 2 micrograms/min altered neither blood pressure nor carotid blood flow. In conclusion, ANP infusion induced changes in systemic and regional hemodynamics varying in direction, intensity and duration.