Angiographic Contrast Media Research Articles

A time-dependent offset field approach to simulating realistic interactions between beating hearts and surgical devices in virtual interventional radiology.

Endovascular interventional radiology (IR) is a minimally invasive procedure for the treatment of vascular diseases. This procedure requires physicians to be highly skilled at manipulating interventional devices under the guidance of two-dimensional X-ray imaging. By offering a non-error-sensitive and radiation-free environment, a virtual reality-based simulator provides a promising alternative for surgical skills training and surgery planning. Building a realistic and interactive simulator is a challenging task. To achieve better realism, this paper proposes a novel method of simulating the heartbeat for both standard and patient-specific anatomical data. A time-dependent offset field approach is proposed to efficiently and stably simulate the interactive behavior between the dynamic heart mesh and surgical devices. For medical imaging simulation, we propose a GPU-based linear depth subtraction method to approximate fluoroscopic images based on the attenuation of the X-ray. On this basis, a topology-based flow map method is proposed to simulate the propagation of the contrast medium in angiography. Experimental results show that the proposed algorithm can simulate heartbeat stably for meshes with varying geometrical shapes and complexities. In efficiency, the dynamic heart mesh can interact with surgical devices stably at 60 frames/s. Under the simulated fluoroscopic imaging effect, the injected contrast medium can realistically visualize both dynamic and static vessels. In a face validity by medical students and clinicians, the category of effectiveness score 8.35 out of 10 on average, demonstrating that our simulator is useful in surgical skills training and surgery planning.

Trends in contrast media research the last 100 years

This review focuses on the trends in contrast media (CM) research published in Acta Radiologica during the last 100 years, since the first edition in 1921. The main topics covered are the developments of iodine- and gadolinium-based CM. Other topics include manganese-based CM for magnetic resonance imaging (MRI) and barium for the investigation of the alimentary tract. From a historic point of view, special CM for use in cholegraphy and myelography are addressed in the review. Today, these imaging procedures are obsolete due to the development of computed tomography, MRI, and ultrasound. The historical use of radioactive thorium-based CM for angiography is also addressed. Furthermore, publications on adverse reactions to CM are reviewed.

Blood flows in tributaries of the portal vein: anatomical and angiographic studies in normal beagle dogs.

Liver anatomy, particularly its vascularization, has been investigated in many studies in dogs. Knowledge of blood flow from the main tributaries of the portal vein (PV) is necessary to explain the preferential sites of secondary lesions within the liver based on the site of the initial malignant lesion. How these flows come together was established in an earlier ex vivo study. Here, we highlight in vivo the blood flows from the main PV tributaries and their distribution in the liver of normal dogs. Portographs of the main PV tributaries were obtained in seven dogs after injection of an angiographic contrast medium. After euthanasia, the livers and their portal vascularization (PV and tributaries) were extracted for a comparative corrosion cast study. Flows were demonstrated in the cranial mesenteric vein, caudal mesenteric vein and splenic vein. However, no proper flow could be distinguished for the gastroduodenal and ileocolic veins. All these tributaries primarily supply the lateral liver lobes (right or left). Most of our observations indicate that the cranial mesenteric, caudal mesenteric and splenic veins primarily supply the right lateral lobe and the caudate process of the caudate lobe and secondarily the left lateral lobe, left medial lobe and the quadrate lobe. The two other tributaries (gastroduodenal and ileocolic veins) primarily supply the right lateral lobe and the caudate process of the caudate lobe.

Thrombin activatable fibrinolysis inhibitor

The slow coronary flow (SCF) phenomenon is characterized by slow progression of angiographic contrast medium in the coronary arteries in the absence of stenosis in the epicardial vessels. The pathophysiological mechanisms of SCF phenomenon remain uncertain. Several hypotheses, however, have been suggested for SCF phenomenon, including an early form of atherosclerosis, small vessel dysfunction, dilatation of coronary vessels, imbalance between vasoconstrictor and vasodilatory factors, platelet function disorder, and inflammation. Atherosclerosis and inflammation are the most accepted mechanisms for the pathogenesis of SCF. Thrombin activatable fibrinolysis inhibitor (TAFI) was described as a new inhibitor of fibrinolysis recently and plays an important role in coagulation and fibrinolysis. In previous studies, the role of TAFI was associated with inflammation and evolution of atherosclerosis in coronary artery disease. There are no data available about TAFI levels in patients with SCF phenomenon investigated by angiography. Our goal was to evaluate TAFI antigen (Ag) levels in patients with SCF and to determine the association of the TAFI Ag level with traditional cardiovascular risk factors in our study. The study group constituted 41 patients with angiographically confirmed SCF and 46 patients with normal coronary flow as the control group. The TAFI Ag levels of each patient were determined. Between the control and study group, a statistical difference in the levels of TAFI Ag (p < 0.05) was observed. The TAFI Ag level was significantly higher in the SCF group than the control group (132.21 ± 21.14 versus 122.15 ± 21.59). We have demonstrated that TAFI might be a risk factor for the development of SCF independently of conventional cardiovascular risk factors. In addition, TAFI Ag levels were positively correlated with C-reactive protein (CRP) known as an acute phase reactant. Our findings support the reports of previous studies that increased TAFI levels may be associated with inflammation. Further large studies are required to evaluate the importance of TAFI antigen levels in relation to the development of SCF.

Ischemic Colitis: Unreported Complication After a Carbon Dioxide Angiogram

Introduction: Carbon dioxide is used as a contrast medium for angiography because it is highly soluble, rapidly absorbed and readily excreted by the lungs. CO2 angiography is used in patients who are allergic to iodinated contrast, have renal insufficiency or require high volume contrast procedures. Notable complications of CO2 angiography include air embolism, neurotoxicity, hypotension, nausea and abdominal discomfort. Transient ischemic colitis has not been reported as complication of CO2 angiography. Case: 75-year-old male with past medical history of hypertension, coronary artery disease (status post coronary artery bypass grafting) and chronic kidney disease presented to the emergency department with lower abdominal pain. The pain started about 30 minutes after CO2 angiography for evaluation of intermittent claudication. The pain was suprapubic and in the left lower quadrant and associated with vomiting. This was followed by bloody mucoid stools. WBC count was elevated at 14.7 with a left shift and the rest of the labs were unremarkable. Abdominal and pelvic CT scan without IV contrast showed diffuse colonic wall thickening in rectosigmoid area. Flexible sigmoidoscopy with an ultra scope showed friable mucosa, nodularity, cobblestoning and mucosal edema in the rectum and sigmoid. The findings were consistent with ischemic colitis. The patient was managed conservatively and improved over the next week and was uneventfully discharged. Conclusion: Ischemic colitis that has been reported after angiography can have potentially life threatening and serious complications. Transient ischemic colitis after CO2 angiography has not been reported before. In this case, the colonic ischemia was self limiting and short lived and responded well to conservative therapy.

Lack of NO formation is involved in the vasodilative response to contrast media

Intravascular injection of angiographic contrast media results in peripheral vasodilation and hypotension. The mechanisms underlying these hemodynamic changes are not entirely clear. We hypothesized that increased formation of nitric oxide (NO) could be involved in the vasodilatory response to contrast media. To address this assumption we have investigated whether N(G)-monomethyl-L-arginine (L-NMMA, 200 mg/kg) and N(G)-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg), two specific NO formation inhibitors, can abolish the hypotensive response to intravascular injection of isopaque amin (1 g/kg), a contrast medium, as well as bradykinin (10 µg/kg), a NO-dependent vasodilator, in anaesthetized normotensive rats. In rats before pretreatment with L-NMMA and L-NAME, the absolute values of the average fall in mean arterial pressure (MAP) induced by intravascular injection of isopaque amin and bradykinin were 21.3 +/- 2.1 and 37.2 +/- 4.4 mmHg, respectively. Pretreatment with L-NMMA and L-NAME failed to affect the hypotensive response to isopaque amin; by administering isopaque amin in rats pretreated with L-NMMA and L-NAME the absolute values of the average fall in MAP were 25.6 +/- 4.9 and 23.4 +/- 3.9 mmHg, respectively, similar to the average fall in MAP before treatment with NO formation inhibitors. In contrast, the hypotensive response to bradykinin was significantly inhibited; by administering bradykinin in rats pretreated by L-NMMA and L-NAME, the absolute values of the average fall in MAP were 10.2 +/- 2.8 and 7.2 +/- 2.2 mmHg, respectively, much less than the average fall in MAP before treatment with NO formation inhibitors. We conclude that intravascular injection of isopaque amin causes reduction in systemic arterial pressure. However, this vasodilative effect seems unrelated majorly to augmented endothelium-derived NO formation.

Whole blood reflectance for assessment of hematologic condition and detection of angiographic contrast media

We present simple whole blood reflectance analyses in the range 500-900 nm, using intact whole blood to simultaneously quantify hematocrit and oxygen saturation from a single spectral reading. We applied these results for the development of an intravascular catheter-based reflectance sensing system to detect and remove contrast media injected during angiography so as to reduce the risk of complications associated with the injected contrast media. We further tested the practicality of the optical detection of angiographic contrast media in a pilot animal study in vivo. We successfully demonstrated the feasibility of real-time in vivo contrast detection and removal during angiography. Our simple method for the detection and removal of angiographic contrast media will facilitate the development of intravascular optical sensing systems.

Local Delivery of Paclitaxel to Inhibit Restenosis during Angioplasty of the Leg

Drug-eluting stents reduce restenosis in coronary arteries, but clinical trials have failed to prove their efficacy in peripheral arteries. We investigated the use of paclitaxel-coated angioplasty balloons and paclitaxel dissolved in the angiographic contrast medium during angioplasty of the leg. In a small, multicenter trial, we randomly assigned 154 patients with stenosis or occlusion of a femoropopliteal artery to treatment with standard balloon catheters coated with paclitaxel, uncoated balloons with paclitaxel dissolved in the contrast medium, or uncoated balloons without paclitaxel (control). The primary end point was late lumen loss at 6 months. The mean (+/-SD) age of the patients was 68+/-8 years, 24% were smokers, and 49% had diabetes. Twenty-seven percent of the lesions were total occlusions, and 36% were restenotic lesions. The mean lesion length was 7.4+/-6.5 cm. There were no significant differences in baseline characteristics between the groups. There were no adverse events attributable to the paclitaxel-coated balloons. At 6 months, the mean late lumen loss was 1.7+/-1.8 mm in the control group, as compared with 0.4+/-1.2 mm (P<0.001) in the group treated with paclitaxel-coated balloons and 2.2+/-1.6 mm (P=0.11) in the group treated with paclitaxel in the contrast medium. The rate of revascularization of target lesions at 6 months was 20 of 54 (37%) in the control group, 2 of 48 (4%) in the group treated with paclitaxel-coated balloons (P<0.001 vs. control), and 15 of 52 (29%) in the group treated with paclitaxel in the contrast medium (P=0.41 vs. control); at 24 months, the rates increased to 28 of 54 (52%), 7 of 48 (15%), and 21 of 52 (40%), respectively. Use of paclitaxel-coated angioplasty balloons during percutaneous treatment of femoropopliteal disease is associated with significant reductions in late lumen loss and target-lesion revascularization. No significant benefit is seen with the use of a paclitaxel-containing contrast medium. (ClinicalTrials.gov number, NCT00156624 [ClinicalTrials.gov].).

A Case of Hypertrophic Cardiomyopathy Complicated by Acute Myocardial Infarction and Ventricular Tachycardia: Slow Coronary Artery Flow

Many patients with hypertrophic cardiomyopathy experience chest pain, and some of these patients are diagnosed with acute myocardial infarction. Acute myocardial infarction in the setting of hypertrophic cardiomyopathy can occur without coronary atherosclerosis. Although the exact pathophysiologic mechanism of this remains unclear, some pathologic studies have suggested that small vessel coronary artery disease in patients with hypertrophic cardiomyopathy may play a major role in producing myocardial ischemia. Small vessel disease can be suspected when the coronary angiogram shows patent epicardial coronary arteries with slow flow of the angiographic contrast medium. We report here on a case of hypertrophic cardiomyopathy that was complicated with acute myocardial infarction, and this induced catastrophic refractory ventricular tachycardia. (Korean Circ J 2008;38:291-294)

The role of osmolality in the incidence of contrast-induced nephropathy: A systematic review of angiographic contrast media in high risk patients

The role of osmolality of contrast media (CM) in the pathogenesis of contrast-induced nephropathy (CIN) has been suggested by studies comparing high osmolality CM (>1500 mOsm/kg) with low-osmolality CM (550-850 mOsm/kg), and by the results of a recent comparison of a CM isotonic to plasma (iodixanol, 290 mOsm/kg) with a low-osmolality CM (iohexol, 844 mOsm/kg) in high-risk patients undergoing cardiac or peripheral angiography. Using prospectively defined search criteria, we performed a systematic overview of prospective, randomized, controlled studies of CIN in renally impaired patients receiving intra-arterial doses of iodixanol or low-osmolality, nonionic CM, and conducted a systematic review of the data from those studies to determine whether the osmolality of CM was predictive of CIN incidence. Seventeen primary studies met the selection criteria, for a total of 1365 patients. Overall, the incidence of CIN was 16.8%. A multivariate logistic regression model showed that the risk of CIN is similar with the iso-osmolality iodixanol and the low-osmolality iopamidol (796 mOsm/kg). The risk of CIN was significantly lower with iodixanol and iopamidol compared to iohexol. The incidence of CIN with iohexol was also significantly higher than with iopamidol, despite their similar osmolalities. These data suggest that factors other than osmolality play a significant role in the pathogenesis of CIN, at least for agents with osmolalities of 800 mOsm/kg or less.

Preoperative MRI of Potential Living-Donor-Related Liver Transplantation Using a Single Dose of Gadobenate Dimeglumine

This article evaluates the feasibility of single-dose gadobenate dimeglumine-enhanced MRI as both an angiographic and biliary contrast medium for making a preoperative evaluation of the donor candidates for a living-donor-related liver transplantation. Eleven right hepatic lobe donors underwent MRI examinations using T1- and T2-weighted imaging and T2-weighted MR cholangiography (MRC). The MR angiography (MRA) and contrast-enhanced (CE) T1-weighted MRC images then were obtained after injecting a single dose of gadobenate dimeglumine. One radiologist and one surgeon prospectively reviewed all the MRI examinations for hepatic vascular and biliary abnormalities and compared them with the surgical findings and intraoperative cholangiograms. In addition, two blinded reviewers evaluated the two sets of MRC (T2-weighted MRC set and T2-weighted MRC plus CE-T1-weighted MRC set) retrospectively and recorded the anatomic types of the hilar biliary branching pattern along with their confidence in the interpretation. Prospective analysis detected the following vascular variants: hepatic arterial variation in two patients, portal venous variation in one, and a significantly large accessory hepatic vein (> 5 mm) in one. Biliary variants also were identified in two patients. All the MRI findings on the vascular and biliary anatomy were corroborated intraoperatively. Retrospective analysis showed that the mean diagnostic confidence in the combined set was significantly higher than that of the T2-weighted MRC alone by both reviewers (p < 0.05). Obtaining both MRA and CE-T1-weighted MRC is feasible using a single dose of gadobenate dimeglumine. Therefore, gadobenate dimeglumine-enhanced MRI might play a role as a preoperative imaging technique for the vascular and biliary evaluation of potential living donors.

Drug Delivery by Angiographic Contrast Media: Inhibition of Restenosis

Angioplasty without and with stent implantation is an established minimally invasive procedure for treating localized stenosis in a variety of blood vessels. A high acute success rate is reduced by restenosis within the following months mainly due to neointimal hyperplasia induced by the unavoidable injury of the vessel wall. Rapamycinand paclitaxel-eluting stents significantly delay or reduce restenosis in animal experiments and patients [1, 2]. According to current concepts sustained release of efficacious antiproliferative drugs is required to achieve this effect [3]. Rapamycin and paclitaxel are highly lipophilic and poorly water-soluble. These agents may rapidly enter the local vessel wall when dissolved in contrast media (CM) and administered for selective angiography during interventional procedures. This may be sufficient to prevent restenosis if high enough local concentrations are reached and suppression of cell proliferation is maintained for the critical period of time following injury. Results reported at the CMR 2001 [4] indicated the efficacy of this approach. Additional studies were designed to investigate the dose dependency of the effects of paclitaxel added to CM in the porcine coronary stent model and to measure local drug concentrations.

Inhibition of restenosis in stented porcine coronary arteries: uptake of Paclitaxel from angiographic contrast media.

Paclitaxel added to angiographic contrast medium (CM) has been shown to inhibit restenosis in the porcine coronary overstretch model. This study determined early local tissue concentrations after the administration of different paclitaxel doses and preparations. Fifteen pigs received 2 stents each in the left coronary artery. During and/or after the intervention, paclitaxel-containing CM or diluted Taxol was injected. Fifteen minutes after the last intracoronary injection, paclitaxel concentrations in the arterial wall and myocardium were measured by high-performance liquid chromatography. Mean paclitaxel concentrations in the left coronary arteries reached 3-10 microM. Higher volumes and higher paclitaxel concentrations resulted in higher tissue concentrations. Paclitaxel in CM was better tolerated and led to higher local concentrations than diluted Taxol. Low paclitaxel concentrations in the uninjected right coronary artery and in plasma indicate selectivity. When admixed to CM, paclitaxel results in local tissue concentrations proportional to the amount of the drug injected.

Neurotoxicity of angiographic carbon dioxide in the cerebral vasculature.

This study was undertaken to resolve conflicting evidence about the neurotoxicity of carbon dioxide gas as an angiographic contrast medium within the cerebral vasculature. Single intracarotid injections or five consecutive intracarotid injections, at 2-minute intervals, of carbon dioxide, iopromide or saline, were given to 32 rabbits under clinically relevant conditions. Extravasation of Evans blue and Tc-pertechnetate was used to determine blood-brain barrier damage at 30 minutes or 6 hours after injection. At 6 hours after multiple injections, brains were removed for histologic examination. A single intracarotid injection of carbon dioxide caused minimal blood-brain barrier breakdown, whereas multiple injections caused significant breakdown that was still present at 6 hours after the injections. All carbon dioxide-injected brains that underwent histologic examination showed evidence of irreversible brain damage in the injected hemisphere. The study confirms the neurotoxicity of carbon dioxide within the cerebral vasculature and its unsuitability for clinical use in cerebral angiography.

Systemic platelet effects of contrast media: Implications for cardiologic research and clinical practice

Background Angiographic contrast media cause platelet activation and decrease aggregability in vitro. We have previously shown in vitro a significant antiplatelet effect of contrast media at the concentrations obtained locally in the coronary artery during angioplasty. It is not known, however, whether a systemic effect is present. Method Thirty patients undergoing diagnostic coronary angiography were prospectively randomized to receive the nonionic medium iohexol, ionic low-molecular-weight medium ioxaglate, or ionic high-molecular-weight medium diatrizoate. Platelet aggregability was measured before and after the investigation with whole blood electrical impedance aggregometry (WBEA) with collagen agonist and the PFA-100 (Dade, Miami, Fla) platelet function analyzer with combined shear, collagen, and adenosine diphosphate as agonists. Results With WBEA, with iohexol no difference in impedance change was seen: (medians and ranges) before, 9.8 Ω (4.8-19.2 Ω) versus after, 9.6 Ω (2-19.2 Ω) (P not significant [NS]). With ioxaglate a significant fall was seen: before, 8.6 Ω (6.4-15.2 Ω) versus after, 6.6 Ω (0-12.4 Ω) (P =.004). With diatrizoate a significant and greater fall was seen: before, 10.8 Ω (6.4-17.6 Ω) versus after, 6.6 Ω (0-10.8 Ω) (P =.002). With PFA, no difference in closure time was seen with any medium: iohexol before, 99 seconds (79-142 seconds) versus after, 142 seconds (63-128 seconds) (P NS); ioxaglate before, 120 seconds (75-258 seconds) versus after, 95 seconds (74-258 seconds) (P NS); and diatrizoate before, 114.5 seconds (65-250 seconds) versus after, 100.5 seconds (72-300 seconds) (P NS). Conclusions Ionic but not nonionic contrast media have a systemic antiplatelet effect at diagnostic angiographic doses when measured with WBEA. Such an effect has not been shown before. This may explain the observed improved clinical outcome with ionic contrast media but also might confound platelet studies in coronary angioplasty. (Am Heart J 2002; 143:e1.)

Use of spiral CT and the contrast medium iohexol to determine in one session aortorenal morphology and the relative glomerular filtration rate of each kidney.

The aim of this study was to determine the relative glomerular filtration rate (GFR), i.e. the GFR of each kidney in percent of total GFR, by spiral CT. In 41 patients, who were part of a follow-up program after endoluminal stent grafting of aortic aneurysm, spiral CT with the contrast medium iohexol was used to evaluate the morphology of the aorta and kidneys. The opportunity was taken to utilize the already injected iohexol to determine the relative GFR with an extra CT sequence. In each patient two determinations were made, 6 or 12 months apart. The amount of a GFR marker accumulating in Bowman's space, tubuli, and renal pelvis within 2-3 min after i.v. injection, before any marker had left the kidney via the ureter, was defined as proportional to the GFR of that kidney. The renal accumulation of iohexol was obtained by spiral CT using 10-mm collimation and a table speed of 10 mm/s (pitch ratio 1:1) from the upper to the lower poles. The correlation coefficient between the relative GFR of each kidney determined at the first and second examination was excellent (r=0.99) with a median (range) difference of 1% (0-6%) of total GFR. The radiation dose calculated as the mean absorbed dose to the kidneys was 50 mGy and the effective dose 5 mSv. The morphology of aorta and kidneys and the relative GFR of each kidney can be determined in one session with spiral CT using iohexol as both angiographic contrast medium and as a GFR marker. It is also possible to take some plasma samples in the same session to determine iohexol concentration to calculate the body clearance of iohexol (or take plasma and urine samples to calculate the renal clearance of iohexol).

Lack of NO formation is involved in the vasodilative response to contrast media

Intravascular injection of angiographic contrast media results in peripheral vasodilation and hypotension. The mechanisms underlying these hemodynamic changes are not entirely clear. We hypothesized that increased formation of nitric oxide (NO) could be involved in the vasodilatory response to contrast media. To address this assumption we have investigated whether NG-monomethyl-L-arginine (L-NMMA, 200 mg/kg) and NG-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg), two specific NO formation inhibitors, can abolish the hypotensive response to intravascular injection of isopaque amin (1 g/kg), a contrast medium, as well as bradykinin (10 μg/kg), a NO-dependent vasodilator, in anaesthetized normotensive rats. In rats before pretreatment with L-NMMA and L-NAME, the absolute values of the average fall in mean arterial pressure (MAP) induced by intravascular injection of isopaque amin and bradykinin were 21.3 ± 2.1 and 37.2 ± 4.4 mmHg, respectively. Pretreatment with L-NMMA and L-NAME failed to affect the hypotensive response to isopaque amin; by administering isopaque amin in rats pretreated with L-NMMA and L-NAME the absolute values of the average fall in MAP were 25.6 ± 4.9 and 23.4 ± 3.9 mmHg, respectively, similar to the average fall in MAP before treatment with NO formation inhibitors. In contrast, the hypotensive response to bradykinin was significantly inhibited; by administering bradykinin in rats pretreated by L-NMMA and L-NAME, the absolute values of the average fall in MAP were 10.2 ± 2.8 and 7.2 ± 2.2 mmHg, respectively, much less than the average fall in MAP before treatment with NO formation inhibitors. We conclude that intravascular injection of isopaque amin causes reduction in systemic arterial pressure. However, this vasodilative effect seems unrelated majorly to augmented endothelium-derived NO formation.

Lack of NO Formation Is Involved in the Vasodilative Response to Contrast Media

Intravascular injection of angiographic contrast media results in peripheral vasodilation and hypotension. The mechanisms underlying these hemodynamic changes are not entirely clear. We hypothesized that increased formation of nitric oxide (NO) could be involved in the vasodilatory response to contrast media. To address this assumption we have investigated whether NG-monomethyl-L-arginine (L-NMMA, 200 mg/kg) and NG-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg), two specific NO formation inhibitors, can abolish the hypotensive response to intravascular injection of isopaque amin (1 g/kg), a contrast medium, as well as bradykinin (10 μg/kg), a NO-dependent vasodilator, in anaesthetized normotensive rats. In rats before pretreatment with L-NMMA and L-NAME, the absolute values of the average fall in mean arterial pressure (MAP) induced by intravascular injection of isopaque amin and bradykinin were 21.3 ± 2.1 and 37.2 ± 4.4 mmHg, respectively. Pretreatment with L-NMMA and L-NAME failed to affect the hypotensive response to isopaque amin; by administering isopaque amin in rats pretreated with L-NMMA and L-NAME the absolute values of the average fall in MAP were 25.6 ± 4.9 and 23.4 ± 3.9 mmHg, respectively, similar to the average fall in MAP before treatment with NO formation inhibitors. In contrast, the hypotensive response to bradykinin was significantly inhibited; by administering bradykinin in rats pretreated by L-NMMA and L-NAME, the absolute values of the average fall in MAP were 10.2 ± 2.8 and 7.2 ± 2.2 mmHg, respectively, much less than the average fall in MAP before treatment with NO formation inhibitors. We conclude that intravascular injection of isopaque amin causes reduction in systemic arterial pressure. However, this vasodilative effect seems unrelated majorly to augmented endothelium-derived NO formation.

Evaluation of angiographic contrast media and platelet function with impedance aggregometry and the PFA-100TM 'platelet function analyser'

Angiographic contrast media are used in balloon angioplasty and may influence thrombotic complications of the procedure. We studied the effect of different media on platelet aggregation in whole blood using impedance aggregometry and the PFA-100 'platelet function analyser' (Dade, USA). Methods: Venous blood samples from 18 healthy volunteers were split into four aliquots and mixed with 10% normal saline control, non-ionic medium (iohexol), low-molecular weight ionic medium (ioxaglate) and high-molecular weight ionic medium (diatrizoate). Samples were studied with impedance aggregometry and the PFA-100. Results: All media caused significant inhibition of aggregation compared with control with both methods (P<0.001). Antiplatelet potency was greatest with diatrizoate, intermediate with ioxaglate and least with iohexol with both methods (P<0.01). Electron microscopy of the PFA-100 membrane demonstrated occlusion of the experimental aperture with platelet thrombus in the control. Inhibition of platelet thrombus was seen with all media, greatest with diatrizoate, intermediate with ioxaglate and least with iohexol. Conclusions: The media studied significantly inhibited platelet aggregation in vitro and potency was greater with ionic than non-ionic media. These methods use a combination of shear and chemical agonist with whole blood and may reproduce in vivo arterial conditions better than other techniques.

High-performance liquid chromatographic determination of the X-ray imaging contrast agent, iofratol, in plasma and urine

Iofratol is currently under evaluation as a potential X-ray contrast medium for angiography and myelography. An HPLC method for assaying iofratol in rat and human plasma and urine samples is described. The analysis is based on the reversed-phase chromatographic separation of iofratol and the internal standard (iopamidol) from the endogenous components of biological fluids, and detection by UV absorption at 242 nm. The selectivity of the method was satisfactory. The mean absolute recovery was greater than 90%. The precision and accuracy of the analytical methods were in the range 0.8–7.4 and −7.8 to +9.7%, respectively. The detection limits in plasma (0.1 ml) and urine (0.5 ml) were 0.1 and 0.4 μg (iofratol)/ml, respectively. The analyte was stable in the different biological matrices when stored at room temperature (20°C) for at least 1 day, 4°C for 1 month and −20°C for 1 year.