Intravenous Targeted Microbubbles Carrying Urokinase versus Urokinase Alone in Acute Peripheral Arterial Thrombosis in a Porcine Model.

BACKGROUND: Standard therapy in acute peripheral arterial occlusion consists of intra-arterial catheter-guided thrombolysis. As microbubbles may be used as a carrier for fibrinolytic agents and targeted to adhere to the thrombus, we can theoretically deliver the thrombolytic medication locally following simple intravenous injection. In this intervention-controlled feasibility study, we compared intravenously administered targeted microbubbles incorporating urokinase and locally applied ultrasound, with intravenous urokinase and ultrasound alone. METHODS: In 9 pigs, a thrombus was created in the left external iliac artery, after which animals were assigned to either receive targeted microbubbles and urokinase (UK + tMB group) or urokinase alone (UK group). In both groups, ultrasound was applied at the site of the occlusion. Blood flow through the iliac artery and microcirculation of the affected limb were monitored and the animals were euthanized 1 hr after treatment. Autopsy was performed to determine the weight of the thrombus and to check for adverse effects. RESULTS: In the UK + tMB group (n = 5), median improvement in arterial blood flow was 5 mL/min (range 0-216). Improvement was seen in 3 of these 5 pigs at conclusion of the experiment. In the UK group (n = 4), median improvement in arterial blood flow was 0 mL/min (-10 to 18), with slight improvement in 1 of 4 pigs. Thrombus weight was significantly lower in the UK + tMB group (median 0.9383 g, range 0.885-1.2809) versus 1.5399 g (1.337-1.7628; P = 0.017). No adverse effects were seen. CONCLUSIONS: Based on this experiment, minimally invasive thrombolysis using intravenously administered targeted microbubbles carrying urokinase combined with local application of ultrasound is feasible and might accelerate thrombolysis compared with treatment with urokinase and ultrasound alone.

Premature aging of the microcirculation in patients with advanced chronic kidney disease.

BACKGROUND: Increasing age and advanced chronic kidney disease (CKD) are both associated with an attenuated vasodilator response of the skin microcirculation. In the present study, we investigated the effect of aging on microvascular reactivity in patients with advanced CKD. METHODS: Acetylcholine (ACh)-mediated endothelium-dependent vasodilation and sodium nitroprusside (SNP)-mediated endothelium-independent vasodilation were assessed by iontophoresis combined with laser Doppler flowmetry. Microvascular function was compared between 52 patients with advanced CKD (stage 4-5: n = 16; end-stage renal disease: n = 36) and 33 healthy control subjects. As aging has an important effect on microvascular function, both control subjects and CKD patients were divided in subgroups younger and older than 45 years. Linear regression analysis was applied to assess potential associations between microvascular function and various demographic and clinical parameters. RESULTS: There were three main findings. (1) In young patients with advanced CKD, both ACh- and SNP-mediated vasodilations were impaired if compared to young healthy controls (p = 0.04 and p = 0.056, respectively). (2) In young patients with advanced CKD, microvascular function was similar to old healthy controls and elderly patients with advanced CKD. (3) Whereas age was inversely associated with microvascular function in healthy controls (log ACh-mediated vasodilation R = -0.41; p = 0.02 and log SNP-mediated vasodilation R = -0.38; p = 0.03), no such relation was found in patients with advanced CKD. CONCLUSIONS: Our results are consistent with premature aging of the microvascular vasodilatory capacity in patients with advanced CKD.

Capillary rarefaction in advanced chronic kidney disease is associated with high phosphorus and bicarbonate levels.

BACKGROUND: In patients with chronic kidney disease (CKD), disorders of mineral metabolism are associated with vascular calcifications and mortality. Microvascular dysfunction, by affecting flow resistance and tissue perfusion, may explain the cardiovascular sequelae of CKD-associated disorders of mineral metabolism. We investigated whether advanced CKD is associated with a decrease in the functional and structural number of capillaries in skin and subsequently whether capillary rarefaction is related to mineral metabolism. METHODS: Capillary density was measured by nailfold microscopy in 19 predialysis and 35 CKD Stage 5 (CKD5) patients and 19 controls. In CKD patients, calcium, phosphorus, parathyroid hormone, 25-hydroxyvitaminD3 (25vitD3) and 1,25-dihydroxyvitaminD3 (1,25vitD3) were analysed as well. RESULTS: Capillary density at baseline was 42 ± 15/mm(2) in predialysis patients, 45 ± 17/mm(2) in CKD5 patients and 56 ± 20/mm(2) in controls (patients versus controls, respectively, P < 0.05 and P = 0.05). Absolute capillary recruitment during post-occlusive reactive hyperaemia was 17 ± 7/mm(2), 14 ± 6/mm(2) and 23 ± 8/mm(2), respectively (P < 0.05 for both patients and controls). Capillary density during venous occlusion was 59 ± 20/mm(2), 59 ± 21/mm(2) and 77 ± 21/mm(2), respectively (P < 0.05 for both patients and controls). In multiple regression analysis, both serum phosphorus and bicarbonate values were independently and inversely associated with capillary density at baseline (r(2) of model = 19%) as well as during venous occlusion (r(2) of model = 28%). Furthermore, both serum phosphorus and bicarbonate were inversely and female gender positively correlated with capillary density during recruitment (r(2) of model = 37%). CONCLUSION: Advanced CKD is characterized by an impaired functional and structural capillary density in skin, which is related to both high phosphorus and bicarbonate values.

ρ-Kinase inhibition reduces early microvascular leukocyte accumulation in the rat kidney following ischemia-reperfusion injury: roles of nitric oxide and blood flow.

AIM: To study whether microvascular leukocyte accumulation after rat renal ischemia and reperfusion (IR) is decreased by Rho kinase inhibition, independently of effects upon nitric oxide (NO) and renal blood flow. METHODS: Male Wistar rats were subjected to 60 min of ischemia by bilateral clamping and 60 min of reperfusion of the renal arteries, or a sham procedure. Haemodynamics were monitored and microsphere blood flow to the kidneys was measured. The infusion of the Rho kinase inhibitor (Y27632) was commenced before clamping and IR. The NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), was administered after the start of reperfusion whilst the dopamine-1 receptor agonist fenoldopam, a renal vasodilator, was infused during the reperfusion period. Digital imaging microscopy analysis of cryosections was done to determine leukocyte accumulation and vasodilator-stimulated phosphoprotein serine 239 phosphorylation (p-VASP ser 239), a marker of endothelial NO. RESULTS: Leukocytes (60-70% neutrophils) accumulated within blood vessels in the corticomedullary junction and medulla of the kidney. Leukocyte accumulation was markedly reduced by the Rho kinase inhibitor but not by fenoldopam. However, both drugs improved renal blood flow and microvascular expression of p-VASP ser 239 in the corticomedullary junction and medulla, which were decreased following IR. L-NAME treatment of IR animals pretreated with the Rho kinase inhibitor reduced blood flow and p-VASP ser 239 expression and increased leukocyte accumulation. CONCLUSION: Early microvascular leukocyte accumulation in the corticomedullary junction and medulla of the rat kidney after IR is ameliorated by Rho kinase inhibition. This effect is partly independent upon attenuation of decreased NO and renal blood flow.

Infrarenal aortic-clamping after renal ischaemia aggravates acute renal failure.

BACKGROUND: Renal failure is a frequent complication of juxtarenal abdominal aortic aneurysm (JAA)-repair. During this operation, suprarenal aortic-clamping is followed by infrarenal aortic-clamping (below renal arteries) to restore renal flow, while performing the distal anastomosis. We hypothesized that infrarenal aortic-clamping, despite restoring renal perfusion provokes additional renal damage. MATERIALS AND METHODS: We studied three groups of rats. After 45min of suprarenal aortic-clamping, group 1 had renal reperfusion for 90min without aortic-clamps (n=7). In group 2, 45min of suprarenal aortic-clamping with a distal clamp on the aortic-bifurcation was followed by 20min of infrarenal aortic-clamping. Renal reperfusion was continued for 70min without aortic-clamps (i.e. 90 min of renal reperfusion; n=8). The sham-group had no clamps (n=7). We measured renal haemodynamics, functional parameters and tissue damage. RESULTS: On suprarenal aortic-clamp removal, renal artery flow, cortical flow and arterial pressures were higher in group 2 than in group 1. We detected increased tubular brush border damage, luminal lipocalin-2 and 30-60% higher renal protein nitrosylation in group 2 when compared to group 1 (P<0·05). Group 2 showed more release of asymmetrical dimethylarginine (ADMA) from the kidneys in the renal vein, therefore indicating diminished clearing capacity (P<0·001). Arginine/ADMA-ratio, which defines the bio-availability of nitric oxide, tended to be lower in group 2 and correlated with renal flow. Furthermore, there were no significant differences found in creatinine levels and renal leucocyte accumulation between group 1 and 2. CONCLUSIONS: Additional infrarenal aortic-clamping leads to increased renal damage and oxidative stress, despite adequate perfusion of kidneys after suprarenal aortic-clamping. This study indicates that the clamping sequence used in JAA-repair causes more than simple renal I/R-injury.

Peritoneal dialysis fluid bioincompatibility and new vessel formation promote leukocyte-endothelium interactions in a chronic rat model for peritoneal dialysis.

Peritoneal dialysis (PD)-induced peritonitis leads to dysfunction of the peritoneal membrane. During peritonitis, neutrophils are recruited to the inflammation site by rolling along the endothelium, adhesion, and transmigration through vessel walls. In a rat PD-model, long-term effects of PD-fluids (PDF) on leukocyte-endothelium interactions and neutrophil migration were studied under baseline and inflammatory conditions. Rats received daily conventional-lactate-buffered PDF (Dianeal), bicarbonate/lactate-buffered PDF (Physioneal) or bicarbonate/lactate buffer (Buffer) during five weeks. Untreated rats served as control. Baseline leukocyte rolling and N-formylmethionyl-leucyl-phenylalanine (fMLP) induced levels of transmigration in the mesentery were evaluated and quantified by intra-vital videomicroscopy and immunohistochemistry. Baseline leukocyte rolling was unaffected by buffer treatment, approximately 2-fold increased after Physioneal and 4-7-fold after Dianeal treatment. After starting fMLP superfusion, transmigrated leukocytes appeared outside the venules firstly after Dianeal treatment (15 minutes), thereafter in Physioneal and Buffer groups (20-22 minutes), and finally in control rats (>25 minutes). Newly formed vessels and total number of transmigrated neutrophils were highest in Dianeal-treated animals, followed by Physioneal and Buffer, and lowest in control rats and correlated for all groups to baseline leukocyte rolling (r = 0.78, P < 0.003). This study indicates that the start of inflammatory neutrophil transmigration is related to PDF bio(in)compatibility, whereas over time neutrophil transmigration is determined by the degree of neo-angiogenesis.

Magnetically navigated percutaneous coronary intervention in distal and/or complex lesions may improve procedural outcome and material consumption.

AIMS: Comparison of magnetic guidewire navigation in percutaneous coronary intervention (magnetic PCI) across distal and/or complex lesions versus conventional navigation (conventional PCI). METHODS AND RESULTS: Forty-seven consecutive patients (age 61 +/- 10 yr) undergoing elective single vessel magnetic PCI for distal and/or complex lesions were matched by age and lesion location with 45 patients undergoing conventional PCI (age 63 +/- 10 yr). Technical success rate was defined as an intraluminal wire position distal to the stenosis. Procedural outcome and costs were evaluated. Baseline demographics and angiographic characteristics of the two groups were similar. The technical success rate did not differ between magnetic and conventional PCI (95.7 vs 97.8%; p = 1.00). Significantly shorter procedural and fluoroscopy time were observed for magnetic compared to conventional PCI (29.9 +/- 17.6 vs 41.1 +/- 21 min, p = 0.007; 7.5 +/- 7.3 vs 16.1 +/- 22.4 min, p = 0.02 respectively). Less contrast was used in the magnetic PCI group (58 ml/patient; P = 0.02). These advantages resulted in a mean estimated saving of 1400 euro per patient (P < 0.001). Advantages of procedural outcome were even more pronounced in the ACC/AHA lesion class C subgroup. CONCLUSIONS: Magnetic compared to conventional PCI is an attractive novel technique that proved to be feasible and safe and might be faster in distal and especially complex lesions.

Circulating white blood cells and platelets amplify oxidative stress in heart failure.

BACKGROUND: Mitochondria of circulating white blood cells (WBC) and platelets sense oxidative stress during capillary passage and react by producing reactive oxygen species (ROS). Although evidence indicates that congestive heart failure (CHF) is associated with oxidative stress, the role of WBC and platelets as mediators in CHF has not been investigated. METHODS: Patients with CHF (n = 15) and healthy volunteers (n = 9) were enrolled between 2006 and 2007 into this observational study. Arterial and venous blood samples from participants were incubated with probes to detect cytosolic and mitochondrial ROS. Fluorescence-activated cell sorting was used to measure the degree of fluorescence in WBC and platelets. RESULTS: Patients with CHF had a higher proportion of ROS-positive arterial WBC and platelets than did controls (67% +/- 47% versus 16% +/- 9%; P <0.005), as well as venous WBC and platelets (77% +/- 43% versus 38% +/- 13%; P <0.01). In the control group, the proportion of cytosolic ROS-positive arterial WBC and platelets was lower than that for ROS-positive venous WBC and platelets (16% +/- 9% versus 38% +/- 13%; P <0.005). CHF patients had a higher proportion of mitochondrial ROS-positive arterial and venous WBC and platelets than did controls. CONCLUSION: In CHF, the proportion of WBC and platelets that are ROS-positive is raised, possibly because cytosolic ROS-positive WBC and platelets are normally cleared in the lungs; this function is deficient in CHF while mitochondrial ROS production is increased. The raised numbers of circulating ROS-positive WBC and platelets amplify oxidative stress in CHF.

Platelet activation in clinical haemodialysis: LMWH as a major contributor to bio-incompatibility?

BACKGROUND: The sum of undesirable side effects, occurring during haemodialysis (HD), is called bio-incompatibility. Concerning platelets, both an increase in the expression of the cell surface marker P-selectin (CD62p) and release of the intracellular granule product platelet factor 4 (PF4) have been described. However, as PF4 is also abundantly present on endothelium-bound proteoglycans, it is questionable whether the HD-induced increase is exclusively attributable to release from platelets. With respect to the cause of HD-induced bio-incompatibility, interest has been focused mainly on the extracorporeal circuit (ECC), especially the dialyser, whereas only little attention has been paid to other parts of the ECC and the mode of anticoagulation applied. To address the cause and origin of platelet activation and PF4 release during clinical HD, two complementary clinical studies were performed. MATERIALS AND METHODS: In study I, the relative influence of the various parts of the ECC was evaluated by measuring the expression of CD62p, platelet aggregation and levels of PF4 and serotonin at various sampling points. In study II, low-molecular-weight heparin (LMWH) was administered 10 min before the actual start of HD, in order to separate the effects from LMWH and the ECC on platelet activation. RESULTS: In study I, CD62p expression increased across the entire length of the ECC, including the roller pump and dialyser (median at t(5) from 26% to 43%, P = 0.008; median at t(30) from 28% to 48%, P = 0.007). Increments in PF4 and aggregation of platelets were relatively modest. Platelet serotonin content, which was below reference values in healthy controls, and plasma serotonin concentration, which was above reference values, did not change. In study II, PF4 levels increased markedly after the injection of LMWH (from 12 IU/ml at t(-10) to 75 IU/ml at t(0), P = 0.018), whereas CD62p expression remained stable until the start of HD. CONCLUSIONS: Platelet activation, as measured by the up-regulation of CD62p, is an early process, occurring not only within the dialyser, but across the entire length of the ECC. As CD62p remained unaltered after the administration of LMWH 10 min before the actual start of HD, this kind of activation is independent of LMWH. Considering PF4 however, a sharp increment was observed after the administration of LMWH and before the start of HD. This finding suggests that the PF4 release observed early in clinical HD is largely independent from the ECC, and is probably the result of LMWH-induced detachment from the endothelium. As the platelet serotonin content was relatively reduced and the plasma serotonin levels were elevated, platelets from chronic HD patients might be depleted due to chronic repetitive activation. Based on these data, it appears first, that PF4 is an inferior marker of platelet activation in clinical HD and second, that LMWH is a major contributor to HD-induced bio-incompatibility.

Mechanisms of the urinary concentration defect and effect of desmopressin during endotoxemia in rats.

Acute renal failure during human sepsis is often nonoliguric. To study the underlying mechanisms, renal function was assessed in endotoxic and control male Wistar rats during and after saline loading and treatment with the selective V2 receptor agonist desmopressin. Escherichia coli endotoxin (dose, 8 mg/kg) was administered from time (t)=0 to t=60 min; saline loading (rate, 5 mL/100 g per hour) was administered from t=0 to t=120 min. Thereafter, half of each group received desmopressin (dose, 10 microg) for 1 h. The inner medullary (IM) osmolality, hematocrit, plasma, and urinary concentrations of sodium, potassium, urea, and osmolality were measured; then, aquaporin 2 (AQP2) immunohistochemistry was performed. Plasma vasopressin concentrations were measured at t=180 min. Saline loading increased urine volume in all rats. In the endotoxic group, mean arterial pressure decreased when saline loading was stopped. Despite increased hematocrit and vasopressin levels (>16 pg/mL), the endotoxin group had a low IM osmolality (mean +/- SEM, 412+/-0.04 mOsm/kg H2O) in comparison with the control group (mean +/- SEM, 1,094+/-0.17 mOsm/kg H2O) and was not able to either decrease urine volume or raise urine osmolality. Desmopressin treatment in endotoxin-treated rats maintained mean arterial pressure, increased sodium reabsorption, IM osmolality, and urine osmolality, and decreased urine flow. The AQP2 intensity decreased in the endotoxin group, and the apical localization disappeared; both were not affected by desmopressin. Our results indicate that endotoxemia in rats acutely diminishes renal urinary concentration capacity and is associated with a decreased IM osmolality and diminished apical AQP2 localization. These findings may help to explain nonoliguric acute renal failure in human septic shock.

Direct vasoconstrictor effect of prostaglandin E2 on renal interlobular arteries: role of the EP3 receptor.

Evidence indicates that prostaglandin E(2) (PGE(2)) preferentially affects preglomerular renal vessels. However, whether this is limited to small-caliber arterioles or whether larger vessels farther upstream also respond to PGE(2) is currently unclear. In the present study, we first investigated the effects of PGE(2) along the preglomerular vascular tree and subsequently focused on proximal interlobular arteries (ILAs). Proximal ILAs in hydronephrotic rat kidneys as well as isolated vessels from normal kidneys constricted in response to PGE(2), both under basal conditions and after the induction of vascular tone. By contrast, smaller vessels, i.e., distal ILAs and afferent arterioles, exhibited PGE(2)-induced vasodilation. Endothelium removal and pretreatment of single, isolated proximal ILAs with an EP1 receptor blocker (SC51322, 1 micromol/l) or a thromboxane A(2) receptor blocker (SQ29548, 1 micromol/l) did not prevent vasoconstriction to PGE(2). Furthermore, in the presence of SC51322, responses of these vessels to PGE(2) and the EP1/EP3 agonist sulprostone were superimposable, indicating that PGE(2)-induced vasoconstriction is mediated by EP3 receptors on smooth muscle cells. Immunohistochemical staining of proximal ILAs confirmed the presence of EP3 receptor protein on these cells and the endothelium. Adding PGE(2) to normal isolated kidneys induced a biphasic flow response, i.e., an initial flow increase at PGE(2) concentrations

Beneficial effects of aminoguanidine on peritoneal microcirculation and tissue remodelling in a rat model of PD.

BACKGROUND: The formation of glucose degradation products (GDPs) and accumulation of advanced glycation end products (AGEs) partly contribute to the bioincompatibility of peritoneal dialysis fluids (PDF). Aminoguanidine (AG) scavenges GDPs and prevents the formation of AGEs. METHODS: In a peritoneal dialysis (PD) rat model, we evaluated the effects of the addition of AG to the PDF on microcirculation and morphology of the peritoneum, by intravital microscopy and quantitative morphometric analysis. RESULTS: AG-bicarbonate effectively scavenged different GDPs from PDF. Daily exposure to PDF for 5 weeks resulted in a significant increase in leucocyte rolling in mesenteric venules, which could be reduced for approximately 50% by addition of AG-bicarbonate (P<0.02). Vascular leakage was found in rats treated with PDF/AG-bicarbonate, but not with PDF alone. Evaluation of visceral and parietal peritoneum showed the induction of angiogenesis and fibrosis after PDF instillation. PDF/AG-bicarbonate significantly reduced vessel density in omentum and parietal peritoneum (P<0.04), but not in mesentery. PDF-induced fibrosis was significantly reduced by AG (P<0.02). PDF instillation led to AGE accumulation in mesentery, which was inhibited by supplementation of AG. Since addition of AG-bicarbonate to PDF raised pH from 5.2 to 8.5, a similar experiment was performed with AG-hydrochloride that did not change the fluid acidity. We could reproduce most of the results obtained with AG-bicarbonate; however, AG-hydrochloride induced no microvascular leakage and had a minor effect on angiogenesis. CONCLUSION: The supplementation of either AG reduced a number of PDF-induced alterations in our model, emphasizing the involvement of GDPs and/or AGEs in the PDF-induced peritoneal injury.

Better preservation of the peritoneum in rats exposed to amino acid-based peritoneal dialysis fluid.

BACKGROUND: Glucose-containing peritoneal dialysis fluids (PDF) show impaired biocompatibility, which is related partly to their high glucose content, presence of glucose degradation products, low pH, and lactate buffer, or a combination of these factors. In a rat chronic peritoneal exposure model, we compared effects of an amino acid-based PDF (AA-PDF) with a glucose-containing PDF on the peritoneal microcirculation and morphology. METHOD: Two groups of rats received 10 mL of either fluid daily for 5 weeks via peritoneal catheters connected to implanted subcutaneous mini vascular access ports. Leukocyte-endothelium interactions in the mesenteric venules were investigated by intravital microscopy. Quantification of angiogenesis and fibrosis and inspection of the mesothelial cell layer were performed by light and electron microscopy. RESULTS: Daily exposure to glucose-containing PDF resulted in a significant increase in the number of rolling leukocytes in mesenteric venules, whereas instillation of AA-PDF did not change the level of leukocyte rolling. Glucose-containing PDF evoked a significantly higher number of milky spots in the omentum, whereas this response was significantly reduced in animals exposed to the AA-PDF (p < 0.02). Chronic instillation of glucose-containing PDF induced angiogenesis in various peritoneal tissues, accompanied by fibrosis in the mesentery and parietal peritoneum. Quantitative morphometric evaluation of omentum and mesentery showed a clear trend toward less angiogenesis after treatment with the AA-PDF compared to the glucose-containing PDF, which reached statistical significance in the parietal peritoneum (p < 0.04). Instillation of AA-PDF resulted in approximately 50% reduction of fibrosis in the mesentery (p < 0.04) and approximately 25% reduction in the parietal peritoneum (p < 0.009) compared to glucose-containing PDF. Glucose-containing PDF damaged the mesothelial cell layer, whereas the mesotheium was intact after AA-PDF treatment, as evidenced by electron microscopy. CONCLUSION: Our data in a rat chronic peritoneal exposure model clearly demonstrate reduced immune activation (evidenced by decreased number of rolling leukocytes and decreased induction of omental milky spots) and reduced neoangiogenesis, fibrosis, and mesothelial damage of the peritoneal membrane after treatment with AA-PDF compared to glucose-containing PDF.

Complete versus culprit vessel percutaneous coronary intervention in multivessel disease: a randomized comparison.

BACKGROUND: The purpose of this study was to compare the safety, efficacy, and costs of complete versus "culprit" vessel revascularization in multivessel coronary artery disease treated with percutaneous coronary interventions (PCI). METHODS: Patients with multivessel disease and an identified culprit vessel were randomly assigned to complete revascularization of vessels > or =50% stenoses (n = 108) versus revascularization limited to the culprit vessel (n = 111). The primary end point, major adverse cardiac events (MACE), were defined as cardiac or noncardiac death, myocardial infarction, need for coronary artery bypass graft surgery, and repeat PCI up to 1 year. RESULTS: Despite equal MACE at 24 hours (6.3% vs 7.4%), strategy success was higher in the culprit vessel than in the complete revascularization group (93.7% vs 81.5%, P =.007). MACE rates at 1 month (14.4% vs 9.3%), 1 year (32.4% vs 26.9%), and 4.6 +/- 1.2 years (40.4% vs 34.6%) were similar in both groups. Repeat PCI was performed more often in the culprit vessel group (31.2% vs 21.2%, P =.06). A lower consumption of medical material was associated with lower procedural costs in the culprit vessel group (5784 vs 7315 Euros; P <.001). However, between 1 year and the end of follow-up, costs had equalized in both groups. CONCLUSIONS: Complete versus culprit vessel revascularization in multivessel coronary disease treated with PCI was associated with a lower strategy success rate, similar MACE rates, and initially higher costs. However, over the long term, more repeat PCIs were conducted in patients treated by culprit revascularization only, mostly because of the need to treat lesions initially left untreated. As a consequence, incremental costs had equalized within 1 year. The decision of whether to perform culprit vessel or complete revascularization can be made on an individual basis.

Impact of operator volume on overall major adverse cardiac events following direct coronary stent implantation versus stenting after predilatation.

OBJECTIVES: To determine the impact of operator experience on procedural, clinical and angiographic outcome after (direct) coronary stent implantation. BACKGROUND: Although for other forms of percutaneous coronary interventions an inverse relationship between operator volume and patient outcomes has been shown, the impact of operator volume on outcome after direct stenting has never been investigated. METHODS: A retrospective analysis was performed on data from a prospective randomized trial comparing direct stenting with that after predilatation. The trial consisted of 400 patients with stable and unstable angina pectoris and/or myocardial ischemia due to a coronary stenosis of a single native vessel eligible in 1999-2001 for direct stenting. For a single-center high-volume clinic (>1500 cases/year), the authors compared the most experienced operators (case load: >4000) with well trained practitioners (case load: 175). One hundred and fifteen patients were identified who were treated by high-volume and 180 who were treated by medium-volume operators. RESULTS: Baseline patient characteristics were evenly distributed among groups. High-volume, compared with medium-volume operators, were faster (30.8 versus 42.2 minutes, p < 0.001), needed less frequent postdilatation (15% versus 24%, p = 0.06) and had lower fluoroscopy times (7.5 versus 11.2 minutes, p < 0.001), lower contrast usage (180 versus 228 ml, p < 0.001), lower procedural costs (euro1982 versus euro2164, p = 0.05) and reduced rates of major adverse cardiac and cerebral event (MACCE) at six months (12.2 versus 21.1%, p = 0.03). The medium-volume operator group experienced higher angiographic binary restenosis rates after direct stenting compared with stenting after predilatation (31.5 versus 14.9%, p = 0.005). CONCLUSIONS: Stenting performed by high-volume operators resulted in a 50% reduction in MACCE as compared with medium-volume physicians, which also had twice as much restenosis when using direct stenting. Hence, the more demanding technique of direct stenting should not be performed by unsupervised operators who have not yet completed their training. Furthermore, prolonged training periods and even more intensive supervision by experienced operators seems mandatory.

Haemodialysis-induced pulmonary granulocyte sequestration in rabbits is organ specific.

BACKGROUND: Haemodialysis (HD) with cuprophan (CU) dialysers leads to a severe transient granulocytopenia. In the present study, we challenge the hypothesis that granulocytes sequester within the pulmonary vasculature simply because this is the first vascular bed encountered. This hypothesis is based upon experiments in which activated plasma or complement fragments were infused into animals, and may not pertain to the more complex HD situation. METHODS: We used a rabbit model of HD, and returned the blood into the caval vein (v-HD) or aorta (a-HD). The mesentery was continuously monitored by intravital video microscopy, whereas other tissues were collected at the nadir of granulocytopenia and analysed immunohistochemically. RESULTS: Compared with controls, the number of granulocytes within alveolar walls was almost 2-fold higher following HD, with no difference between venous and arterial blood return. In addition, both v-HD and a-HD induced granulocyte accumulation within part of the larger pulmonary microvessels, though the amount of granulocytes found was 2-fold higher after v-HD. At no time did a-HD induce granulocyte sequestration within the mesenteric microcirculation. Neither did arterial return increase their number in other first-pass tissues like skeletal muscle or renal glomeruli, but it did so in the liver. In the heart, granulocyte content decreased during HD. CONCLUSIONS: Pulmonary sequestration of granulocytes during CU HD is not simply a first-pass effect, but is organ specific to a great extent. The accumulation within larger microvessels suggests an important role for adhesion molecules, whereas cellular stiffening may be involved in granulocyte retention within alveolar capillaries.

Renal microvascular actions of angiotensin II fragments.

In the present study, we investigated renal microvascular responses to ANG-(1-7) and ANG IV. Diameter changes of small interlobular arteries, afferent arterioles, and efferent arterioles were assessed by using isolated perfused hydronephrotic rat kidneys. ANG-(1-7) and ANG IV concentration dependently decreased the diameters of all investigated renal microvessel, however, with a much lower potency than ANG II. The ANG II type 1 receptor blocker irbesartan completely reversed the responses to ANG-(1-7) and ANG IV, whereas the ANG II type 2 receptor blocker PD-123319 had no effect. Both ANG-(1-7) and ANG IV failed to alter renal microvascular constriction induced by ANG II. In addition, subnanomolar concentrations of ANG-(1-7) had no effect on the myogenic-induced tone of interlobular arteries and afferent arterioles. Thus our data indicate that at high concentrations, ANG-(1-7) and ANG IV are able to activate the ANG II type 1 receptor, thereby inducing renal microvascular constriction. The failure of ANG-(1-7) and ANG IV to reduce ANG II- and pressure-induced constrictions suggests that these fragments do not exert a vasodilator and/or ANG II antagonistic action in the kidney.

Reduced reactivity of renal microvessels to pressure and angiotensin II in fawn-hooded rats.

Fawn-Hooded rats possess an increased risk to develop glomerular damage. Both an impaired control of preglomerular resistance and an elevated postglomerular resistance have been implicated. In the present study, we directly assessed the myogenic reactivity of distal interlobular arteries and afferent arterioles from hypertensive and normotensive Fawn-Hooded rats compared with Sprague-Dawley and Wistar rats, which are known to be resistant for developing renal disease. Pressure-response curves were made in isolated perfused hydronephrotic kidneys from these rats. In addition, increasing concentrations of angiotensin II were added to the perfusate to determine the reactivity of interlobular arteries, afferent arterioles, and efferent arterioles to this peptide. Preglomerular vessels from hypertensive and normotensive Fawn-Hooded rats exhibited an impaired reactivity to both pressure and angiotensin II compared with that of Sprague-Dawley and Wistar rats. Basal efferent arteriolar diameters were similar among the 4 strains of rat. In addition, efferent arterioles from hypertensive and normotensive Fawn-Hooded rats displayed a reduced sensitivity to angiotensin II. Our observations demonstrate that in Fawn-Hooded rats, 2 components of preglomerular resistance control are impaired: the myogenic and the angiotensin II response. In addition, efferent arteriolar reactivity to angiotensin II is not elevated but lowered in these rats. Therefore, a deficit in preglomerular resistance control is the most important intrinsic factor involved in the increased susceptibility of Fawn-hooded rats to develop renal disease.

Increased leukocyte rolling in newly formed mesenteric vessels in the rat during peritoneal dialysis.

OBJECTIVE: Long-term peritoneal dialysis (PD) is associated with the development of functional and structural alterations of the peritoneal membrane. The present study reports the effects of chronic exposure to PD fluid on mesenteric leukocyte-endothelium interactions, using intravital video microscopy. METHODS: Rats (n = 7) received 10 mL lactate-buffered 3.86% glucose-containing PD fluid daily during a 5-week period via a subcutaneously implanted mini access port that was connected via a catheter to the peritoneal cavity. In a first control group (n = 8), catheters were implanted but no fluid was instilled; a second control group (n = 8) remained untreated. The number of rolling and adherent leukocytes as well as blood flow and other fluid dynamic variables were analyzed in mesenteric postcapillary (diameter 10-25 mu) and collecting (diameter 26-40 mu) venules. Neovascularization was semiquantitatively assessed after inspection of video images and by light and electron microscopy. Using FITC-labeled albumin, microvascular leakage was examined. RESULTS: Rats exposed to PD fluid showed a more than twofold increase in the number of rolling leukocytes (p < 0.01); the number of adherent leukocytes was not changed. Furthermore, exposure to PD fluid induced severe neovascularization in rat mesentery. No microvascular leakage was observed in the various groups. The observed differences could not be explained by differences in systemic or local hemodynamic parameters or peripheral leukocyte counts, but is most likely associated with new vessel formation. CONCLUSIONS: Exposure of rat peritoneal membrane to conventional PD fluid for 5 weeks affected local leukocyte-endothelium interactions. In addition, severe angiogenesis was induced, whereas microvascular permeability remained unaltered.

Comparison of the AT1-receptor blockers candesartan, irbesartan and losartan for inhibiting renal microvascular constriction.

Angiotensin II (Ang II) type 1 (AT1) receptor blockers differ in their affinity for the AT1-receptor, suggesting a dissimilar potency for inhibiting Ang II-induced vascular constriction. In the present study, we compared the effects of candesartan, irbesartan and losartan on the renal microvascular constriction to locally-formed Ang II, using isolated, perfused hydronephrotic rat kidneys. Addition of 1 nmol/L angiotensin I (Ang I, the precursor of Ang II) significantly reduced the diameters of interlobular arteries (ILAs; -47.6±2.6%), afferent arterioles (AAs; -43.6±2.3%) and efferent arterioles (EAs; -31.6±2.4%). Candesartan and irbesartan were more potent in antagonising the constriction to Ang I than losartan. By contrast, candesartan and irbesartan differed only slightly in potency. After a washing period of 60 minutes with drug-free medium, a second application of Ang I failed to induce vasoconstriction only in candesartan-treated kidneys. Pretreatment of hydronephrotic kidneys with candesartan, to further explore its antagonistic properties, shifted the dose-response curves of Ang II approximately 2 log units to the right without reducing the maximal Ang II-induced constriction of ILAs, AAs or EAs. Additionally, dose-response curves of Ang II were similar after short (10 minutes) and prolonged (60 minutes) preincubation with candesartan. Our findings indicate that candesartan and irbesartan are more potent inhibitors of renal microvascular constriction to locally-formed Ang II than losartan. The inhibitory effect of candesartan is more prolonged, suggesting a slow dissociation from the AT1-receptor. Additionally, candesartan was found to block the Ang II-induced constriction of renal microvessels in a surmountable manner.