Quantitative imaging of microvascular permeability in a rat model of lipopolysaccharide-induced sepsis: evaluation using cryostatic micro-computed tomography

OBJECTIVES: The aim of the present study was to evaluate the magnitude of endothelial defects by micro-computed tomography (CT) quantitation of contrast agent diffusion across the vascular endothelium in a rat model of vascular permeability caused by lipopolysaccharide (LPS)-induced sepsis. MATERIALS AND METHODS: LPS was administered intraperitoneally (i.p.) at a dose of 10 mg/kg body weight in male Wistar rats (n = 18). Vascular leakage and vascular volume were quantified, by micro-CT and cryostatic micro-CT. The contrast agents used were Fenestra ( approximately 70-nm particle diameter), Microfil (large polymer), and iopamidol (Isovue, MW 777 Dalton). RESULTS: Micro-CT revealed an increase in endothelial permeability as indicated by entry of contrast agent (Fenestra) into the extravascular space after LPS administration (P < 0.01). Endotoxin exposure also induced a decrease of vascular luminal volume in the myocardium, liver, kidney, and colonic wall determined by micro-CT (P < 0.01). Vascular leakage, expressed as the ratio of extravascular to intravascular gray scale intensity (IE/II) after injection of contrast agent, increased significantly in the myocardium, liver, kidney, and colonic wall (P < 0.001). The elimination of iopamidol from the intravascular compartment in LPS-challenged rats was decreased compared with control rats. The endothelial defect size was estimated to be >70 nm and <1 microm. CONCLUSION: Contrast agents are useful to characterize vascular leakage and vascular volume fraction in an animal model of endotoxin priming.     

Nitric oxide protects against contrast media-increased pulmonary vascular permeability in rats

RATIONALE AND OBJECTIVES: Nitric oxide (NO) regulation of endothelial function is involved in the development of acute lung injury. The role of NO in contrast media-induced increases in pulmonary vascular permeability was investigated in a rat model. METHODS: Nonionic (iohexol) and ionic (ioxaglate) contrast media were intravenously injected at 1.5 mL/min in rats. Pulmonary vascular permeability was evaluated by measuring the amount of Evans blue dye uptake as a quantitative marker of albumin extravasation in lung tissue. RESULTS: Intravenous injections of contrast media at doses of 4 and 6 g I/kg induced a dose-dependent increase in pulmonary vascular permeability. L-Arginine (an NO synthase substrate) and N(G)-nitro-L-arginine (L-NNA) (an NO synthase inhibitor) prevented and aggravated, respectively, the increase in pulmonary vascular permeability induced by the contrast medium. An aggravating action of L-NNA was confirmed by morphological and histological observations, this action being blocked by L-arginine (300 mg/kg) but not by D-arginine. Isosorbide dinitrate (1-20 mg/kg), an NO donor, had a dose-dependent protective effect on ioxaglate-increased vascular permeability. CONCLUSIONS: Our experimental findings suggest that contrast media at high doses produce pulmonary edema by inhibiting endothelial NO production, and nitrovasodilators protect against this adverse effect in rats.     

Contrast media increase vascular endothelial permeability by inhibiting nitric-oxide production.

RATIONALE AND OBJECTIVES: Contrast media induce adverse effects including edema of the face, glottis, or lung. The endothelial function is maintained by nitric oxide (NO). The present study was designed to elucidate the role of NO in mediating endothelium-related adverse effects of contrast media. METHODS: Human microvascular endothelial cells grown on a Transwell membrane were incubated with iohexol or ioxaglate in the absence or presence of N(G)-monomethyl-L-arginine or sodium nitroprusside. After washing cells, the permeability of sodium fluorescein or Evans blue albumin and the accumulation of NO(2)(-) was examined. RESULTS: Contrast media (50-150 mgI/mL) dose-dependently increased the permeability coefficient by 30% to 230% and inhibited the formation of NO(2)(-) by 40% to 80%. Sodium nitroprusside and N(G)-monomethyl-L-arginine produced protective and aggravating effects on contrast media-increased permeability, respectively. CONCLUSIONS: The present study suggested that contrast media increase vascular endothelial permeability by inhibiting NO production, leading to vascular endothelium-related adverse effects of contrast media.     

Neurotoxicity of non-ionic X-ray contrast media after intracisternal administration in rats

The neurotoxicity of an X-ray contrast medium appears inversely related to the hydrophilicity of the agent. To further test this hypothesis, four non-ionic X-ray contrast agents, differing in hydrophilicity, (ioversol, iopromide, iohexol and iopamidol) were injected into the cisternal magna of ether-anesthetized rats. lopromide demonstrated an acute median lethal dose of 122 mg I/kg. Other signs of toxicity included convulsions, apnea, dyspnea and hypoactivity. In contrast, ioversol, iohexol and iopamidol caused no deaths when administered intracisternally, up to a dose of 1000 mg I/kg. Animals treated with these nonionic agents displayed signs of convulsions, apnea, dyspnea, chewing and hypoactivity. Iopromide possesses a hydrophilicity (e.g., water to octanol partition coefficient) approximately 8.5 times smaller than ioversol, 4.6 times smaller than iohexol and 2.3 times smaller than iopamidol. These data support the hypothesis that tri-iodinated X-ray contrast materials with smaller degrees of hydrophilicity produce greater toxicity to the central nervous system.     

Spiral CT angiography of the abdominal aorta. Comparison of iodixanol and ioversol

RATIONALE AND OBJECTIVES: Enhancement characteristics of a nonionic, dimeric, isotonic contrast medium (iodixanol [Visipaque]) were compared with a nonionic, monomeric contrast medium (ioversol [Optiray]) of the same iodine concentration in spiral computed tomography angiography (CTA) of the abdominal aorta. METHODS: Spiral CTA was performed in 78 patients referred for suspected renal artery stenosis (n = 35) and abdominal aortic aneurysm (n = 43). A test bolus was used to time the scan delay, and all patients were injected with 150 ml contrast medium (320 mgI/ml) of either iodixanol (n = 40) or ioversol (n = 38). Contrast enhancement was measured in the aorta, renal arteries, and renal parenchyma. RESULTS: All mean aortic enhancement was slightly higher with iodixanol than ioversol, measured at three different levels (celiac trunk 315 Hounsfield units [HU] versus 300 HU, renal arteries 325 HU versus 312 HU, aortic bifurcation 276 HU versus 266 HU). However, none of them were statistically significant (e.g., P = 0.26 at the celiac trunk level). Similar results were observed in renal artery and parenchyma enhancements. CONCLUSIONS: Iodixanol and ioversol had similar enhancement characteristics in the early arterial phase. Both substances were well tolerated and seem to be well suited for spiral CTA.     

The effect of sodium on the fibrillatory propensity of nonionic contrast media

Removing sodium from standard ionic contrast media markedly increases the incidence of ventricular fibrillation in patients undergoing coronary angiography. Newer nonionic contrast media, iopamidol, iohexol, and ioversol contain only trace amounts of sodium. To determine whether sodium attenuates or potentiates ventricular fibrillation from nonionic contrast media, we measured the prolongation in QT interval and performed programmed electrical stimulation with one, two and three extra ventricular stimuli in 40 dogs during 4-mL intracoronary injections of iopamidol, iohexol, and ioversol. Solutions of each contrast medium with added NaCl at concentrations of 0.225%, 0.45%, and 0.9% were compared with standard contrast media. The addition of NaCl markedly increased the amount of QT interval prolongation produced by each contrast medium. With iopamidol, the amount of QT interval prolongation was 40 +/- 11 msec with standard iopamidol, but was 58 +/- 11 msec with 0.225% NaCl/iopamidol, 84 +/- 17 msec with 0.45% NaCl/iopamidol, and 132 +/- 42 msec with 0.9% NaCl/iopamidol (P less than .001). Similar results were seen with iohexol and ioversol. Ventricular fibrillation was difficult to induce with standard solutions of these agents (even with three extra stimuli), but became progressively easier to induce when NaCl was added. Three extra stimuli produced ventricular fibrillation in zero of 11 dogs with standard iopamidol, zero of 11 with 0.225% NaCl/iopamidol, three of 11 with 0.45% NaCl/iopamidol, and eight of 11 with 0.9% NaCl/iopamidol (P less than .001). Similar results were observed with iohexol and ioversol. The addition of choline chloride or dextrose did not increase ventricular fibrillation and QT interval prolongation. It is concluded that standard preparations of nonionic contrast media have a very low fibrillatory propensity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preliminary study and clinical evaluation method of ioversol in angiocardiography--establishment of safety evaluation parameters and reliability of radiographic quality evaluation

A multi-center clinical study of a new nonionic iodinated contrast medium (ioversol) was performed in 26 patients undergoing left ventriculography (LVG) and coronary angiography (CAG) at four centers. The aims of this study were to try to establish a clinical evaluation method on contrast media in angiocardiography and to determine radiographic efficacy and safety of ioversol. The reliability of the method evaluating the radiographic quality of the contrast medium was also examined with statistical analysis. Excellent radiographic efficacy was observed with ioversol and morphological diagnosis was possible in all cases. The electrocardiograms (ST-segment deflection, T-wave amplitude, QT interval, corrected QT interval, arrhythmia and heart rate) and the hemodynamic parameters (left ventricular systolic and end diastolic pressures, left ventricular dp/dt max, aortic systolic and diastolic pressures) indicated no clinically significant changes. This study suggested that the monitoring of the ECGs and hemodynamic parameters for up to three minutes after injection of the contrast medium is sufficient for the evaluation in LVG and CAG, and that the monitoring in CAG during the first injection into each left and right coronary artery is also sufficient for the purpose. Heat sensation during injection was mild. A patient had a symptom of nausea after ioversol administration, but it was mild and transient and resolved spontaneously. There were no abnormal clinical laboratory data related to ioversol. The reliability of the radiographic quality evaluated by the individual clinical investigators was considered to be high and adaptable. However, the evaluation in the blinded cinefilms by the committee members involving all investigators would be more preferable for the higher objectivity. The study results suggest that ioversol is considered to be the efficacious and safe contrast medium for the cardiovascular angiography.     

Hemodynamic and electrocardiographic effects of ioversol during cardiac angiography. Comparison with iopamidol and diatrizoate

We studied the hemodynamic and electrocardiographic responses to left ventriculography and coronary arteriography with three angiographic contrast agents. Two were nonionic agents (ioversol 32% iodine, 60 patients, and iopamidol 37% iodine, 30 patients). The third was a conventional ionic agent (diatrizoate 37% iodine, 30 patients). Cardiovascular hemodynamics and the electrocardiogram were recorded for 5 minutes after left ventricular injection and for 2 minutes after coronary injections. Following left ventriculography, diatrizoate caused a greater increase in cardiac output, left ventricular end diastolic pressure, and corrected QT interval while causing a greater decrease in arterial pressure than did either ioversol or iopamidol, which were indistinguishable from each other. Following left coronary arteriography, diatrizoate caused a significant decrease in heart rate, prolongation of the corrected QT interval, and increase in T wave amplitude. In contrast, neither ioversol nor iopamidol caused significant changes in any electrocardiographic parameters. Adverse reactions were more common with diatrizoate than with either ioversol or iopamidol. There were no recognizable differences in angiographic image quality among the three agents. We conclude that the angiographic performance of ioversol is equivalent to that of iopamidol and that both cause less hemodynamic and electrocardiographic disturbance than diatrizoate.     

Preliminary European intravenous clinical experience with a new, low osmolar, nonionic contrast medium: ioversol (Optiray).

The intravenous clinical trial program of ioversol (Optiray), a low osmolar, nonionic, monomeric contrast agent characterized by high hydrophilicity, is evaluated on the basis of results from the first clinical trials conducted in Europe as part of the development of the 300 and 350 mgI/ml formulations: 7 double-blind, comparative trials and 5 single trials were performed in a total of 743 patients, of whom 472 received ioversol and 271 a monomeric nonionic reference product. The diagnostic efficacy of ioversol was equivalent or superior to that of the reference products and tolerance was comparable to that of nonionic agents in terms of pain and heat sensations. No significant difference in adverse reactions was found and all the contrast agents studied were well tolerated by the patients.     

Pathophysiologic basis of contrast enhancement in breast tumors.

While the diagnostic benefits of gadolinium (Gd)-chelate contrast agents are firmly established in magnetic resonance imaging (MRI) of tumors, the pathophysiologic basis of the enhancement observed and its histopathologic correlate remained vague. Tumor angiogenesis is fundamental for growth and metastasis and also of interest in new therapeutic concepts. By correlative analysis of a) histology; b) vascular density (CD31); and c) vascular permeability (vascular permeability factor/vascular endothelial growth factor [VPF/VEGF]), we found a) significantly (P < 0.001) faster exchange rates in malignant compared with benign breast lesions; b) distinct differences in enhancement characteristics between the histologic types (invasive ductal carcinoma, invasive lobular carcinoma, and ductal carcinoma in situ); and c) dependence of enhancement kinetics on the VPF/VEGF expression. The pathophysiologic basis for the differences in contrast enhancement patterns of tumors detectable by MRI is mainly due to vascular permeability, which leads to more characteristic differences than vascular density. MRI is able to subclassify malignant breast tumors due to their different angiogenetic properties.     

Blood pool MR contrast agents for cardiovascular imaging

Currently available magnetic resonance (MR) contrast agents are not confined to the intravascular space because of their small molecular size. These agents produce peak vascular enhancement for only a short period. Conversely, blood pool agents have longer intravascular residence time and higher relaxivity. Therefore these agents provide MR angiography with flexibility, versatility, and accuracy. With blood pool agents, the timing of contrast injection becomes less significant because the optimal imaging window is in tens of minutes rather than seconds. In addition, larger anatomic regions can be imaged optimally. Preliminary evidence appears to support the notion that blood pool agents may play a diagnostic role in coronary, peripheral, and pulmonary angiography. Besides their ability to increase vascular contrast, blood pool agents provide physiologic information, including rate of entry, rate of accumulation, and rate of elimination. MR imaging with blood pool agents also have proven to be of significant value in the assessments of myocardial perfusion and microvascular permeability. In anticipation of broad clinical use, blood pool agents are currently being evaluated in human trails. Examples include gadolinium-chelate that binds in vivo to albumin to form blood pool agents and ultrasmall superparamagnetic iron oxide particles. This review discusses the applications of MR blood pool agents in the cardiovascular system. J. Magn. Reson. Imaging 2000;12:890-898.     

Ioversol. Double-blind study of a new low osmolar contrast agent for peripheral and visceral arteriography

The new low-osmolar contrast agent ioversol was compared with the conventional ionic contrast agent diatrizoate in 60 patients undergoing routine abdominal (21 patients) and peripheral (39 patients) arteriography. The effects on hemodynamics, various laboratory parameters, and patient comfort were evaluated. In peripheral arteriography, there was less discomfort with ioversol as well as decreased magnitude and incidence of hypotension (P less than .001) after injection. In visceral arteriography, there was no significant difference between the two agents. Overall, the incidence of ECG changes was small in both groups (ioversol 2%, diatrizoate 8%). The two media were equivalent in incidence of adverse reactions (eg, nausea, vomiting, urticaria), the effect on laboratory parameters, and in the diagnostic adequacy of the radiographs. We conclude that ioversol is safe and efficacious for peripheral and visceral arteriography. In peripheral arteriography it causes less patient discomfort and, perhaps more importantly, fewer hemodynamic alterations than diatrizoate. These differences in hemodynamic effects may be important in patients with hemodynamic instability or limited cardiovascular reserve.     

New macromolecular polymeric MRI contrast agents for application in the differentiation of cancer from benign soft tissues

PURPOSE: To compare three new macromolecular polyethylene glycol (PEG) -core dendrimeric gadolinium(Gd)-based MRI contrast agents for their applicability in quantitative assays of endothelial leakiness and tissue vascular density for the differentiation of cancer from normal soft tissues. MATERIALS AND METHODS: Thirty-two athymic rats with human breast cancer xenografts (MDA-MB-435) were imaged by dynamic MRI following enhancement with one of three new (Gd-DOTA)-conjugated PEG-core dendrimer contrast agents (effective molecular weights 161 to 323 kDa). Results were compared with a prototype macromolecular contrast agent, albumin (Gd-DTPA). Assays of permeabilities (K(PS); microL/min . 100 cm(3)) and tumor fractional plasma volumes (%) based on a two-compartment kinetic model were performed for skeletal muscle and tumors. RESULTS: The largest PEG-core contrast agent, PEG(20,000)-Gen4-(Gd-DOTA), leaked in breast tumors (K(PS) = 50 +/- 23 microL/min . 100 cm(3)), while exhibiting no measurable transendothelial leak (K(PS) = 0 microL/min . 100 cm(3)) in normal soft tissue microvessels allowing successful differentiation (P < 0.05) of cancers from normal muscle. PEG(12,000)-Gen4-(Gd-DOTA) leaked in tumors and in normal muscle (K(PS) = 51 +/- 26 and K(PS) = 21 +/- 18 microL/min . 100 cm(3), respectively). The smallest agent, PEG(12,000)-Gen3-(Gd-DOTA) also showed a measurable leak in both normal and malignant microvessels. CONCLUSION: MRI assays of vascular endothelial leakiness using new PEG-core, (Gd-DOTA)-conjugated macromolecular contrast agents proved applicable for the differentiation of human breast cancer from normal soft tissue. The apparent threshold in effective molecular weight for a clear differentiation of cancer from normal muscle with no measurable leak in the muscle is between 194 and 323 kDa.     

Double-blind study of a new nonionic contrast agent for cardiac angiography

A randomized, double-blind study of a new nonionic contrast agent (ioversol) was performed in 80 patients undergoing routine coronary angiography and left ventriculography. Its hemodynamic and electrocardiographic (ECG) effects were compared with those of a conventional ionic contrast agent (sodium meglumine diatrizoate). There were 40 patients in each group. The radiographic quality and incidence of adverse reactions were comparable for both agents. Following left ventriculography, there was a smaller decrease in systemic and left ventricular systolic blood pressure and a smaller increase in heart rate and pulmonary artery systolic pressure (P less than .05) with ioversol than with meglumine diatrizoate. There was also a slight decrease in cardiac output with ioversol at 1 and 3 minutes after left ventriculography, while meglumine diatrizoate produced a modest increase. In selective coronary angiography, the fall in diastolic blood pressure was also greater (P less than .05). The Q-T interval was more prolonged with meglumine diatrizoate. Ioversol appears to be both safe and efficacious for cardiac angiography, causing fewer and less severe hemodynamic and ECG alterations than meglumine diatrizoate.     

贝那普利、氨氯地平、卡维地洛对主动脉内皮细胞单层脂类通透性的影响

目的探讨血管紧张素转换酶抑制剂贝那普利、钙离子拮抗剂氨氯地平和β-受体阻滞剂卡维地洛对大鼠主动脉内皮细胞单层通透性的影响。方法分离培养大鼠主动脉内皮细胞(AEC):将AEC培养在混合纤维素酯微孔滤膜上,8 d后形成AEC单层进行通透性测定。将长有AEC的滤膜分别用上述三药处理4 h,置于灌注装置上,用含异硫氰酸荧光素标记白蛋白的高脂血灌注,测定收集液的量和白蛋白、总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白(HDL)、低密度脂蛋白(LDL)浓度。结果贝那普利、氨氯地平能够降低AEC单层对水、TC,TG,HDL,LDL的通透性(P<0.01);氨氯地平降低AEC单层对TC,LDL的通透性更为显著(P<0.001),卡维地洛作用不明显;只有氨氯地平能够降低AEC单层对白蛋白的通透性。结论贝那普利、氨氯地平可减少血浆中脂类渗入血管内皮下,具有潜在的抗动脉粥样硬化作用。     

Correlative dynamic contrast MRI and microscopic assessments of tumor vascularity in RIP‐tag2 transgenic mice

The purpose of this study was to define the feasibility of dynamic contrast‐enhanced magnetic resonance imaging (MRI) to estimate the vascular density and leakiness of spontaneous islet cell tumors in RIP‐Tag2 transgenic mice. Dynamic T₁‐weighted spoiled gradient echo (SPGR) imaging at 2.0 T was performed in 17 RIP‐Tag2 mice using a prototype blood pool macromolecular contrast medium (MMCM), albumin‐(Gd‐DTPA)₃₅. Kinetic analysis of the dynamic enhancement responses based on a two‐compartment model was used to estimate fractional plasma volume (fPV) and the coefficient of endothelial permeability (K^PS) for each tumor. The MRI estimate of fPV was correlated on a tumor‐by‐tumor basis with corresponding microscopic measurements of vascular density. The fPV assays by MMCM‐enhanced imaging ranged from 2.4%–14.1% of tissue volume. Individual tumor fPV values correlated significantly (r = 0.79, P < 0.001) with the corresponding microscopic estimates of vascularity consisting of the combined area densities of lectin‐perfused microvessels plus erythrocyte‐stained blood lakes. A biotinylated derivative of the albumin‐based MMCM confirmed extravasation of the contrast agent from some tumor blood vessels and accumulation in 25% of blood lakes. The K^PS values ranged from 0 (no detectable leak) to 0.356 mL/min/100 cm³. Dynamic MMCM‐enhanced MRI is feasible in RIP‐Tag2 pancreatic tumors, yielding estimates of vascular permeability and microscopically validated measurements of vascular richness. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Ioversol for intravenous urography: A comparison study

A new nonionic, low-osmolar iodinated contrast media, ioversol, was compared with another low-osmolar, nonionic contrast media, iohexol, in 80 patients undergoing intravenous urography. There were 40 patients in each contrast group. Patients were assessed for changes in vital signs, patient tolerance (heat and pain), and other adverse effects. Double-blind evaluation was also performed for comparison of the urogram image quality. There were no severe, life-threatening reactions for either contrast group. Ten patients (25%) receiving ioversol and seven (17.5%) receiving iohexol perceived body heat related to the injection of contrast material. Two patients (5%) in each group experienced mild nausea. Two patients (5%) of each group experienced noted unpleasant taste, and two patients (5%) of the iohexol group complained of headache. Vital signs remained stable without significant change in both groups, and image quality was considered equivalent. The results indicate that the two contrast agents are equivalent in image quality, safety, and incidence of adverse effects.     

Dynamic contrast-enhanced MR imaging kinetic parameters and molecular weight of dendritic contrast agents in tumor angiogenesis in mice

PURPOSE: To evaluate the relationship between dynamic contrast agent-enhanced magnetic resonance (MR) imaging-derived kinetic parameters and contrast agents of equal chemical composition and configuration but with different molecular weights in a tumor angiogenesis model. MATERIALS AND METHODS: This study was approved by the ethical review committee. Maintenance and care of animals was in compliance with guidelines set by the institutional animal care committee. Dynamic contrast-enhanced MR imaging was performed with dendritic contrast agents in 16 mice with tumor xenografts; mice were placed in groups of four for each molecular weight of the contrast agent. The magnitude and spatial distribution of kinetic parameters (transfer coefficient [K(PS)] and plasma fraction [f(PV)]) were compared with molecular weight of the contrast agent by determining the Spearman correlation coefficient (r) and the quantitative relationship between the endothelial K(PS) and molecular weight. RESULTS: Inverse relationships between molecular weight of contrast agent and K(PS) and f(PV) of tumor rim (r = -0.8, P < .001 and r = -0.5, P = .04, respectively) and core (r = -0.7, P = .004 and r = -0.6, P = .01, respectively) were observed. The quantitative relationship between K(PS) and molecular weight (MW) was K(PS) = 0.4/MW(0.44). A decreasing stepwise pattern in f(PV) was noted between contrast agents with low (0.7- and 3.0-kDa) molecular weight and those with high (12- and 51-kDa) molecular weight. CONCLUSION: Macromolecular permeability is best measured with high-molecular-weight contrast agents; endothelial K(PS) values measured with low-molecular-weight contrast agents incorporate tissue perfusion and permeability and demonstrate heterogeneous microcirculatory flow.     

High performance liquid chromatography with multiwavelength detection: a technique for identification of iodinated x-ray contrast agents in human body fluids and brain tissue.

PURPOSE: Several cases of a severe adverse reaction, referred to as "ascending tonic-clonic seizure syndrome," have been reported after administration of water-soluble iodinated x-ray contrast agents for myelographic examinations. Because of the bizarre reactions, the identities of the causative contrast media were questioned. METHODS: Analyses of biologic materials from four of these patients were performed by using reverse-phase high-performance liquid chromatography. The chromatographic system was equipped with a fast-scanning UV-visible detector for the analysis of the UV-spectra of the chromatographic peaks. RESULTS: The analyses revealed that the nonionic contrast agents iohexol or ioversol were not present in detectable amounts in any of the samples. On the other hand, the chromatographic analyses revealed peaks that cochromatographed with and showed the same UV-spectra as the ionic agents diatrizoate, metrizoate, and ioxitalamate. CONCLUSION: The results indicate inadvertent injection of ionic contrast medium in all four cases.     

Effects of nitinol Strecker stent placement on vascular response in normal and stenotic porcine iliac arteries

PURPOSE: This experimental study was conducted to evaluate neointimal thickness, lumen diameters, and histologic changes in normal and stenotic porcine iliac arteries following placement of self-expanding nitinol Strecker stents. MATERIALS AND METHODS: Neointimal trauma causing slight vascular stenosis was induced unilaterally within external iliac arteries of 12 swines by means of endothelial abrasion and high cholesterol diet. Nitinol Strecker stents were placed within the stenotic and the normal contralateral vascular segments. For histopathologic evaluation, the pigs were killed 12 or 24 weeks after stent placement and luminal diamters were evaluated angiographically. RESULTS: Excluding one occlusion, 15% narrowing of the lumen diameter was induced unilaterally (P = .002). Initial luminal gain after stent placement was greater for stenotic than for normal arteries. The amount of neointima thickness was not different between stenotic and normal vessels (P > .05). Comparing vascular diameters before stent placement and at follow-up, luminal loss due to neointima proliferation was 22% within normal arteries (P = .0002), while a luminal gain by 15% was found within the stenotic arteries (P = .008). Maturation of neointima and endothelial coverage were complete after 24 weeks. CONCLUSIONS: Even though nitinol Strecker stents induce excessive neointimal proliferation, stenotic arteries seem to profit from great early luminal gain resulting in 15% of vascular expansion at follow-up while slight stenosis is induced within normal iliac arteries.