Contrast media for angiography: physicochemical properties, pharmacokinetics and biocompatibility

Contrast-Induced Acute Kidney Injury: Evidence in Support of Its Existence and a Review of Its Pathogenesis and Management

The role of contrast-induced nephropathy (CIN) remains controversial. Many experts contend that CIN does not exist or is extremely rare. The diagnosis was previously made too frequently and inappropriately in the presence of coexisting and confounding comorbidities and risk factors making it difficult to singularly isolate the etiologic role of intravenous contrast media in acute kidney injury (AKI). It is probable that many patients were denied important diagnostic information from radiocontrast studies for fear of CIN. Recently, a new terminology for CIN was introduced, and the term CIN was replaced by two interrelated new terms: one is contrast-associated acute kidney injury (CA-AKI), and the second one is contrast-induced acute kidney injury (CI-AKI). CA-AKI occurs in association with risk factors or comorbidities, therefore, it is a correlative diagnosis. On the other hand, CI-AKI is a subtype of CA-AKI that results directly from iodinated contrast media. In this review, we present evidence from various studies that argue against CI-AKI and also those that suggest its existence but with much lower frequency. We will also provide the current status of the pathophysiology and management of CA-AKI/CI-AKI.

Finding the Optimal Alternative for Immediate Hypersensitivity to Low-Osmolar Iodinated Contrast

OBJECTIVES

Avoiding culprit agents is recommended for subjects who have had previous hypersensitivity reaction (HSR) to low-osmolar contrast media (LOCM). However, the guidelines for choosing optimal alternatives have not been determined. We investigated the outcomes of reexposure in patients with previous immediate HSRs to provide a safe option.

MATERIALS AND METHODS

The outcomes of reexposure were assessed in a cohort with previous LOCM-associated HSR based on skin testing results and the presence of a common N-(2,3-dihydroxypropyl) carbamoyl side chain.

RESULTS

Among 482 skin tests, 38.7% (31/80), 45.8% (99/216), and 64.0% (119/186) of mild, moderate, and severe index HSRs showed positivity to at least 1 LOCM, of which 62.8% showed positivity to at least 2 different LOCM. The overall recurrent HSRs were reduced from 43.8% upon reexposure to the culprit LOCM to 12.3% upon using nonculprit skin test negative LOCM (P = 0.004); those with severe index HSRs exhibited a significant reduction (11.3% vs 100%), but those with non-severe HSRs to LOCM did not. In subjects with severe index HSRs, the skin test cross-reactivity between LOCM was associated with sharing the common side chain (20.7% vs 11.5%, P = 0.003), and the recurrence rate of HSRs was effectively reduced by avoiding the common side chain (24.0% vs 7.8%, P = 0.039). However, these differences were not observed in those with non-severe index HSRs.

CONCLUSIONS

In patients who experienced a severe index HSR to LOCM, skin test negative LOCM without a common side chain could be suggested as an option for safe reexposure.

Thermal plasma activation and UV/H2O2 oxidative degradation of pharmaceutical residues

The aquatic environment becomes increasingly contaminated by anthropogenic pollutants such as pharmaceutical residues. Due to poor biodegradation and continuous discharge of persistent compounds in sewage water samples, pharmaceutical residues might end up in surface waters when not removed. To minimize this pollution, onsite wastewater treatment techniques might complement conventional waste water treatment plants (WWTPs). Advanced oxidation processes are useful techniques, since reactive oxygen species (ROS) are used for the degradation of unwanted medicine residues. In this paper we have studied the advanced oxidation in a controlled laboratory setting using thermal plasma and UV/H₂O₂ treatment. Five different matrices, Milli-Q water, tap water, synthetic urine, diluted urine and synthetic sewage water were spiked with 14 pharmaceuticals with a concentration of 5 μg/L. All compounds were reduced or completely decomposed by both 150 W thermal plasma and UV/H₂O₂ treatment. Additionally, also hospital sewage water was tested. First the concentrations of 10 pharmaceutical residues were determined by liquid chromatography mass spectrometry (LC-MS/MS). The pharmaceutical concentration ranged from 0.08 up to 2400 μg/L. With the application of 150 W thermal plasma or UV/H₂O₂, it was found that overall pharmaceutical degradation in hospital sewage water were nearly equivalent to the results obtained in the synthetic sewage water. However, based on the chemical abatement kinetics it was demonstrated that the degree of degradation decreases with increasing matrix complexity. Since reactive oxygen and nitrogen species (RONS) are continuously produced, thermal plasma treatment has the advantage over UV/H₂O₂ treatment.

Galenic pial arteriovenous fistulas: Angioarchitecture, clinical presentation, and therapeutic considerations

Vein of Galen (VG) aneurysmal malformations (VGAMs) are complex vascular lesions. Their etiopathogenesis is extensively debated and remains poorly understood. Strictly speaking, true VGAMs are Galenic pial arteriovenous fistulas. They are believed to arise in utero and are contended to drain either into the true VG or the median prosencephalic vein of Markowski. Several classification systems have been proposed and are widely used. With the advent of endovascular therapy, precise understanding of the angioarchitecture is critical for management and therapeutic decision making. We review clinical presentation and diagnostic imaging findings, discussing angioarchitectural properties as they relate to treatment planning. Clin. Anat. 31:259-268, 2018. © 2017 Wiley Periodicals, Inc.

Evaluation of Visualization Using a 50/50 (Contrast Media/Glucose 5% Solution) Technique for Radioembolization as an Alternative to a Standard Sandwich Technique

BACKGROUND

Radioembolization (RE) with ⁹⁰yttrium (⁹⁰Y) resin microspheres generally employs a sandwich technique with separate sequential administration of contrast medium (CM), followed by vehicle (e.g., glucose 5% [G5] solution), then ⁹⁰Y resin microspheres (in G5), then G5, and then CM again to avoid contact of CM and microspheres under fluoroscopic guidance. This study evaluates the visualization quality and safety of a modified sandwich technique with a 50/50-mixture of CM (Imeron 300) and G5 for administration of ⁹⁰Y resin microspheres.

MATERIALS AND METHODS

A retrospective analysis of 81 RE procedures in patients with primary or secondary liver tumors was performed. The quality of angiographic visualization of the hepatic vessels was assessed before the first injection and immediately before the whole dose has been injected. Visualization and flow rate were graded on a 5-point scale: 1 = very good to 5 = not visible/no antegrade flow. Univariate logistic regression models and multiple linear regression models were used to evaluate the prognostic variables associated with visualization and flow scores.

RESULTS

Visualization quality was inversely related to flow rate, the lower the flow rate the better the grade of the visualization. Visualization quality was also inversely related to body-mass-index (BMI). Performing RE with the 50/50-CM/G5 mixture resulted in a mean injection time for 1 GBq of 15 min. No clinically significant adverse events, including radiation-induced liver disease were reported.

CONCLUSION

RE with a 50/50-mixture of CM and G5 for administration of ⁹⁰Y resin microspheres in a modified sandwich technique is a safe administration alternative and provides good visualization of hepatic vessels, which is inversely dependent on flow rate and BMI. Injection time was reduced compared with our experience with the standard sandwich technique.

Coagulation, Fibrinolysis, and Platelet Activation Following Open Surgical or Percutaneous Angioplasty Revascularization for Symptomatic Lower Limb Chronic Ischemia

Introduction:

Critical limb ischemia (CLI) is associated with a prothrombotic diathesis that involves a complex balance between the coagulation and fibrinolytic systems. Knowledge of this is essential when considering revascularization procedures but is often overlooked. The aim of this review is to summarize the available literature and provide an overview of the effects of lower limb angioplasty and open surgical revascularization on coagulation, fibrinolysis, and platelet activation.

Methods:

A MEDLINE and EMBASE search was conducted between 1973 and 2014 for articles relating to the effects of revascularization for patients with CLI on the fibrinolytic and coagulation pathways. Studies with a small cohort of patients (<5) were rejected.

Results:

Many of the studies included in this analysis had small cohorts. Multiple markers were assessed across the published literature including von Willebrand factor, tissue factor, prothrombin fragments 1 and 2, platelets, soluble platelet selectin, plasminogen activator inhibitor 1, tissue plasminogen activator, and thrombin–antithrombin complex. Percutaneous intervention causes an exaggerated prothrombotic and a disturbed fibrinolytic effect. Surgery seems to cause a similar prothrombotic derangement with reduced fibrinolysis and platelet hyperactivity, but this appears to be maintained for a considerable amount of time postoperatively.

Conclusion:

There is a sparse amount published on the effects of the coagulation and fibrinolytic systems in patients undergoing intervention for CLI. Much of these studies are small, historical, and completely heterogeneous, making it difficult to draw meaningful conclusions. The literature does identify a prothrombotic state in patients with CLI, which appears to be exacerbated by any form of intervention and prolonged in those having surgery. Understanding this may allow us to tailor the intervention offered to patients and prevent limb loss.

Influence of iodinated contrast media on the activities of histamine inactivating enzymes diamine oxidase and histamine N-methyltransferase in vitro

BACKGROUND

Iodinated contrast media can cause pseudoallergic reactions associated with histamine release in significant numbers of patients. To clarify whether these adverse reactions may be aggravated by a compromised histamine catabolism we asked if radiographic contrast agents in vitro inhibit the histamine inactivating enzymes diamine oxidase (DAO) and histamine N-methyltransferase (HMT).

METHODS

Nine iodinated contrast agents were tested in vitro. Following pre-incubation of purified porcine kidney DAO and recombinant human HMT with 0.1-10mM of the respective contrast medium (H2O and specific inhibitors of DAO and HMT as controls) enzyme activities were determined by using radiometric micro assays.

RESULTS

None of the contrast media irrespective of their structure showed significant inhibition of the activities of DAO and HMT. Pre-incubation of the enzymes with specific inhibitors led to complete inhibition of the respective enzymatic activity.

CONCLUSIONS

The iodinated contrast media tested in vitro did not exhibit inhibition of histamine converting enzymes at physiologically relevant concentrations. However due to the in vitro character of this study these results do not directly reflect the in vivo situation.

Effect of the radiographic contrast material iopamidol on hemostasis: an observational study in thirty cardiac patients

BACKGROUND

In vitro studies have shown that nonionic radiographic contrast material may induce the generation of thrombin in blood, whereas ionic contrast agents, such as iohexol, do not. However, knowledge of the effects of contrast material on coagulation and fibrinolytic systems in vivo is limited.

OBJECTIVE

This study was designed to assess the effects of the nonionic radiographic contrast material iopamidol on hemostasis in patients undergoing coronary angiography or cardiac catheterization.

METHODS

Patients aged ≥18 years with chest pain and/or dyspnea who underwent coronary angiography or cardiac catheterization with intra-arterial contrast material were assessed for hemostasis. Blood samples were drawn before and 3 minutes after injection of iopamidol. Complete blood count and coagulation profile (bleeding time, clotting time, clot retraction time, euglobulin lysis time [ELT], prothrombin and partial thromboplastin times, coagulation factor I [CFI] level, and platelet factor 3 [PF-3] availability) were assessed. The natural coagulation inhibitors protein C, protein S, and antithrombin III (AT-III) also were measured.

RESULTS

Thirty patients (7 males, 23 females; mean [SD] age, 51.3 [20.2] years; range, 17-79 years) were included in this single-center study. All hematologic variables (hemoglobin, white blood cell count, and platelet count) decreased significantly (P<0.001, P<0.001, and P<0.05, respectively) after administration of iopamidol but remained within normal limits. Mean levels of protein C, protein S, and AT-III did not change significantly after administration of iopamidol. Bleeding time was not changed significantly, and PF-3 availability was prolonged in both groups, but the changes were not statistically significant.

CONCLUSIONS

In this study population, although hemostasis remained grossly intact after injection of nonionic contrast material, the coagulation system may have been affected by the accelerated consumption of CFI and platelets. The affected variables were platelets, clot retraction time, ELT, and natural coagulation inhibitors (protein C, protein S, and AT-III). Although the natural coagulation inhibitors remained within the normal range, the correlations were found significant. These changes in hemostasis affected the vascular phase. If the vascular compartment, especially the endothelium, remained intact, the infusion of nonionic agents in low concentrations might be safe for angiography and other procedures; however, more studies are needed.

Contrast media viscosity versus osmolality in kidney injury: lessons from animal studies

Iodinated contrast media (CM) can induce acute kidney injury (AKI). CM share common iodine-related cytotoxic features but differ considerably with regard to osmolality and viscosity. Meta-analyses of clinical trials generally failed to reveal renal safety differences of modern CM with regard to these physicochemical properties. While most trials' reliance on serum creatinine as outcome measure contributes to this lack of clinical evidence, it largely relies on the nature of prospective clinical trials: effective prophylaxis by ample hydration must be employed. In everyday life, patients are often not well hydrated; here we lack clinical data. However, preclinical studies that directly measured glomerular filtration rate, intrarenal perfusion and oxygenation, and various markers of AKI have shown that the viscosity of CM is of vast importance. In the renal tubules, CM become enriched, as water is reabsorbed, but CM are not. In consequence, tubular fluid viscosity increases exponentially. This hinders glomerular filtration and tubular flow and, thereby, prolongs intrarenal retention of cytotoxic CM. Renal cells become injured, which triggers hypoperfusion and hypoxia, finally leading to AKI. Comparisons between modern CM reveal that moderately elevated osmolality has a renoprotective effect, in particular, in the dehydrated state, because it prevents excessive tubular fluid viscosity.

Preclinical assessment of a zwitterionic tantalum oxide nanoparticle X-ray contrast agent

Tantalum oxide nanoparticles show great potential as the next generation of X-ray contrast media. Recently, we reported advances in tantalum oxide nanoparticles and identified improvements that were required for such particles to progress further. Namely, the viscosity of concentrated particles, the amount of retention in reticuloendothelial (RES) tissues, and the effect of large quantities of particles on the kidneys after administration were all identified as critical factors which needed further study, understanding, and development. Here, we report on a zwitterionic siloxane polymer nanoparticle coating that reduced the viscosity of concentrated solutions of particles by a factor of 5, decreased tissue retention of injected particles by a factor of 10, and, importantly, did not induce pathological responses in the kidneys.

Does the application of X-ray contrast agents impair the clinical effect of intravenous recombinant tissue-type plasminogen activator in acute ischemic stroke patients?

BACKGROUND AND PURPOSE

Experimental data suggest a negative interaction between x-ray contrast agents and fibrinolytic efficacy of recombinant tissue-type plasminogen activator (rtPA). We hypothesized that the application of a contrast agent before intravenous thrombolysis with rtPA reduces its clinical efficacy in acute ischemic stroke.

METHODS

We retrospectively studied consecutive ischemic stroke patients receiving contrast agents for computed tomography angiography before intravenous treatment with rtPA. We compared functional outcomes with an historical control group from the Canadian Alteplase for Stroke Effectiveness Study who did not receive contrast agents before thrombolysis with rtPA. Primary end point was favorable functional outcome at 90 days defined as modified Rankin Scale scores 0 to 2. We performed logistic regression analysis and a propensity score matching analysis to estimate the effect size of contrast agent use as a negative predictor of outcome.

RESULTS

We identified 111 patients for the computed tomography angiography and 1119 patients for the control group. Proportions of favorable functional outcome were 47.7% (53/111 patients) for the computed tomography angiography group and 49.5% (542/1094 patients) for the control group (P=0.77). Adjusted probabilities for favorable outcome were 0.48 (95% CI, 0.37-0.58) and 0.51 (95% CI, 0.47-0.54), respectively. Contrast use was associated with reduced odds of favorable outcome (OR, 0.62(;) 95% CI, 0.38-0.99). Propensity score matching suggested a larger effect size (OR, 10.0%; 95% CI, 0.5%-19.3%).

CONCLUSIONS

Our study did not show a significant negative clinical effect of x-ray contrast agents applied before intravenous thrombolysis with rtPA. However, to confirm a possible small negative interaction between contrast agents and rtPA, additional experimental and prospective clinical studies are needed.

Contrast-induced kidney injury: mechanisms, risk factors, and prevention

In general, iodinated contrast media (CM) are tolerated well, and CM use is steadily increasing. Acute kidney injury is the leading life-threatening side effect of CM. Here, we highlight endpoints used to assess CM-induced acute kidney injury (CIAKI), CM types, risk factors, and CIAKI prevention. Moreover, we put forward a unifying theory as to how CIAKI comes about; the kidney medulla's unique hyperosmolar environment concentrates CM in the tubules and vasculature. Highly concentrated CM in the tubules and vessels increases fluid viscosity. Thus, flow through medullary tubules and vessels decreases. Reducing the flow rate will increase the contact time of cytotoxic CM with the tubular epithelial cells and vascular endothelium, and thereby damage cells and generate oxygen radicals. As a result, medullary vasoconstriction takes place, causing hypoxia. Moreover, the glomerular filtration rate declines due to congestion of highly viscous tubular fluid. Effective prevention aims at reducing the medullary concentration of CM, thereby diminishing fluid viscosity. This is achieved by generous hydration using isotonic electrolyte solutions. Even forced diuresis may prove efficient if accompanied by adequate volume supplementation. Limiting the CM dose is the most effective measure to diminish fluid viscosity and to reduce cytotoxic effects.

Pathophysiology of renal tissue damage by iodinated contrast media

1. The present review focuses on the cytotoxic effects of iodinated contrast media (CM) that are shared by all types of CM. 2. Although the clinical nephrotoxicity of CM has been progressively improved, all currently available CM still possess a level of cytotoxicity, which is probably caused by iodine. 3. The toxicity caused by specific CM properties, such as osmolarity, viscosity and ionic strength, can be differentiated from the cytotoxicity common to all CM in studies using cell culture, isolated blood vessels and isolated tubules. 4. The cytotoxicity induced by CM leads to apoptosis and cell death of endothelial and tubular cells and may be initiated by cell membrane damage, together with oxidative stress. 5. Cell damage may be aggravated by factors such as tissue hypoperfusion and hypoxia, properties of individual CM, such as ionic strength, high osmolarity and/or viscosity, and clinically unfavourable conditions. 6. Clinically detectable renal failure may result from the summation of all these factors.

Iodinated contrast media and the role of renal replacement therapy

Iodinated contrast media are among the most commonly used pharmacologic agents in medicine. Although generally highly safe, iodinated contrast media are associated with several adverse effects, most significantly the risk of acute kidney injury, particularly in patients with underlying renal dysfunction. By virtue of their pharmacokinetic characteristics, these contrast agents are efficiently cleared by hemodialysis and to a lesser extent, hemofiltration. This has led to research into the capacity for renal replacement therapies to prevent certain adverse effects of iodinated contrast. This review examines the molecular and pharmacokinetic characteristics of iodinated contrast media and critically analyzes data from past studies on the role of renal replacement therapy to prevent adverse effects of these diagnostic agents.

Contrast-induced nephropathy after intravenous administration: fact or fiction?

Recent prospective clinical investigations in high-risk patients receiving intravenous contrast media for computed tomography (CT) suggest that the incidence and serious negative clinical outcomes are much less common than previously believed. Additional perspectives comparing random variations in serum creatinine in subjects not receiving contrast media show similar fluctuations that would equate to contrast-induced nephrotoxicity (CIN). Putative mechanisms for how CIN could cause death or other serious adverse clinical consequences have not been elucidated.

Similar inhibition of platelet adhesion, P-selectin expression and plasma coagulation by ioversol, iodixanol and ioxaglate

Contrast media (CM) are reported to possess both prothrombotic and anticoagulant properties. The mechanisms are not clearly understood, and early reports are contradictory. To study the effects of CM on haemostasis, we analysed the ex vivo effects of ioversol and iodixanol on platelet adhesion and P-selectin expression, and the in vitro effects of ioversol, iodixanol and ioxaglate on platelet adhesion, P-selectin expression and plasma coagulation. A novel enzymatic assay was used to measure platelet adhesion to protein surfaces, and an enzyme-linked immunosorbent assay was used to measure platelet P-selectin surface expression. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were used to measure plasma coagulation. The ex vivo study consisted of blood from 27 outpatients administered ioversol and 9 patients administered iodixanol intravenously. Samples were collected before and 5 min after CM administration. Healthy donors were used for the in vitro studies on the effects of CM. The ex vivo study showed significantly (p<0.05) decreased platelet adhesion and P-selectin expression after administration of ioversol and iodixanol. Adhesion was more affected than P-selectin expression. The in vitro study showed that ioversol, iodixanol and ioxaglate significantly (p<0.05) and dose-dependently (beginning at 3 mg ml(-1)) decreased platelet adhesion and P-selectin expression. APTT and PT were significantly (p<0.01) prolonged at concentrations of 10 mg ml(-1) and 30 mg ml(-1), respectively. In conclusion, ioversol, iodixanol and ioxaglate inhibit platelet adhesion and P-selectin expression, as well as plasma coagulation. Platelets are more sensitive in relation to the inhibiting effect on plasma coagulation.

[Immediate allergy to iodinated contrast agents and prevention of reactions]

The incidence and morbimortality of immediate hypersensitivity reactions following iodinated contrast media (ICM) injection remain unknown. The diagnosis of an immediate hypersensitivity reaction relies on a triad associating the precise description of the initial clinical manifestations and their delay of onset, the results of the biological assessment performed after the reaction including histamine and tryptase serum level measurements, and the results of skin testing with the culprit agent. Analysis of these data allows identification of the pathophysiologic mechanism of the reaction and the allergen involved in case of allergic hypersensitivity. Skin tests should be performed according to strict criteria. Cross-reactivity with ICM has to be investigated in order to propose a nonreactive ICM for future procedures. Allergic hypersensitivity to a given ICM imposes its definitive avoidance but not the avoidance of all iodinated drugs. The allergenic sequence has not yet been identified but is not the iodine atom itself. Asthma and treatment with beta-blockers are not risk factors of immediate allergic reactions to ICM per se, but may increase their severity. The various published protocols of premedication do not prevent the occurrence of an allergic/anaphylactic reaction to an ICM. The avoidance of the culprit ICM is the only way to prevent further reactions.

Contrast-induced nephrotoxicity: clinical landscape

Over 80 million doses of iodinated intravascular contrast media (CM) were administered in the most recent tabulations of 2003, corresponding to approximately 8 million liters, making it one of the highest volume medical drugs used compared to any other pharmaceutical. The evolution of CM has focused on minimizing adverse events by eliminating ionicity, increasing hydrophilicity, lowering osmolality and increasing the number of iodine atoms per molecule. Contrast media are classified into three general categories based on their osmolality relative to blood: high osmolar (5 times or greater than blood), low osmolar (2-3 times blood) and iso-osmolar (the same as blood). All imaging modalities that employ CM, especially computerized tomography (CT), have shown rapid growth. In the last two decades, the use of CT scanning has increased by 800%. From 1979 to 2002, the number of cardiac catheterization procedures in the USA increased by 390% and in Europe from 1992 to 1999 by 112%. There is a general consensus that renal insufficiency and diabetes are major risk factors for contrast-induced nephropathy (CIN), particularly when co-existing. The US Renal Data System documents a 'relentless' increase in kidney failure, projecting a 90% increase by 2010. Diabetes affects 194 million people worldwide and the number is anticipated to increase by 75% by 2025. The unavoidable conclusion is that patient exposure and prevalence of risk factors for CIN will continue to increase.

Safety of iobitridol in the general population and at-risk patients

The purpose of this study was to review the rate of adverse events after contrast medium administration in the general population and at-risk patients (renal impairment, heart failure (NYHA III or IV), hypotension or hypertension, coronary artery disease, previous reaction to contrast media, asthma and/or allergies, dehydration, diabetes mellitus, poor general condition) under daily practice conditions in a post-marketing surveillance study. Two hundred and ten radiologists conducted various X-ray examinations in 52,057 patients. To document the safety of iobitridol in routine use, all patients undergoing X-ray examinations were included. Exclusion criteria were contraindications listed in the locally approved summary of product characteristics. The adverse event rate was 0.96% (at-risk patients 1.39%); the rate of serious adverse events 0.044% in all patients (at-risk patients 0.057%). Adverse events occurred more often in women than in men (P < 0.001). In patients who had previously reacted to a contrast medium, adverse events were reported in 3.43% with mild to moderate symptoms. In 47.76% of these patients, a premedication was administered. There was no difference in the frequency of adverse events and serious adverse events whether premedicated or not (P = 0.311 and P = 0.295, respectively). Iobitridol was well-tolerated in 99.04% of cases (at-risk patients 98.61%).

Effects of iodinated contrast media on blood and endothelium

The aim of the study was to assess the effects of iodinated contrast media on blood components and endothelium based on experimental and clinical studies and to produce clinically relevant guidelines for reducing thrombotic and hematologic complications following the intravascular use of contrast media. A report was drafted after review of the literature and discussions among the members of the Contrast Media Safety Committee of the European Society of Urogenital Radiology. The final report was produced following discussion at the 12th European Symposium on Urogenital Radiology in Ljubljana, Slovenia (2005). Experimental data indicate that all iodinated contrast media produce an anticoagulant effect and that this effect is greater with ionic contrast media. Several of the in vitro and experimental in vivo studies on haematological effects of contrast media have not been confirmed by clinical studies. Low- or iso-osmolar contrast media should be used for diagnostic and interventional angiographic procedures, including phlebography. Meticulous angiographic technique is the most important factor for reducing the thrombotic complications associated with angiographic procedures. Drugs and interventional devices that decrease the risk of thromboembolic complications during interventional procedures minimize the importance of the effects of contrast media.

Allergy-like reactions to iodinated contrast agents. A critical analysis

Allergy-like reactions may occur following administration of iodinated contrast media (CM), mostly in at-risk patients (patients with history of previous reaction, history of allergy, co-treated with interleukin-2 or beta-blockers, etc.) but remain generally unpredictable. Severe and fatal reactions are very rare events. All categories of CM may induce such reactions, although first generation (high osmolar CM) have been found to induce a higher rate of adverse events than low osmolar CM. However, no differences were found between the two categories of CM with respect to mortality. Delayed reactions can also occur. There are no differences between the various categories of CM except for non-ionic dimers, which are more likely to induce such effect. Numerous clinical studies have evaluated the prophylactic value of drugs (mostly antihistamines and corticosteroids). Results are unclear and highly variable. Any prevention depends upon the mechanism involved. However, the mechanism of CM-induced allergy-like reaction remains disputed. Relatively recent data revived the hypothesis of a type-I hypersensitivity mechanism. Positive skin tests to CM have been reported. However, the affinity of IgE towards CM has been found to be very low in the only study which actually evaluated it. Other pathophysiological mechanisms (involving direct secretory effects on mast cells or basophils, or activation of the complement system associated or not with the plasma contact system) are also much debated. Anaphylaxis and anaphylactoid reactions are, in the end, clinically undistinguishable.

The cytotoxicity of iodinated radiocontrast agents on renal cells in vitro

A deterioration of renal function is one preoccupying complication of iodinated radiocontrast agents in clinical practice. These compounds have direct toxic effects on renal cells, which are only in part related to their physicochemical properties. The hyperosmolal monomeric ionic radiocontrast agents, like diatrizoate, have the highest toxicity, whereas renal cells are less affected by (nonionic) compounds with reduced osmolality. The toxic effects include cellular energy failure, a disruption of calcium homeostasis, a disturbance of tubular cell polarity and programmed cell death (apoptosis). The molecular mechanisms of the direct cytotoxicity are still unclear, although oxidative stress has been implicated. Radiocontrast cytotoxicity has been demonstrated in glomerular mesangial cells and in renal epithelial cells in vitro. In vivo, the direct cellular toxicity of radiocontrast agents is compounded with alterations in blood flow and/or viscosity, ultimately resulting in renal medullary hypoxia, which is a hallmark feature of the complex clinical syndrome of radiocontrast nephropathy.

Differential effects of the iodinated contrast agents Ioxaglate, Iohexol and Iodixanol on thrombus formation and fibrinolysis

INTRODUCTION

Contrast media (CM) possess both pro-thrombotic and anticoagulant properties. Here we investigate the effect of three classes of CM; Iohexol, Iodixanol and Ioxaglate, on thrombus formation and fibrinolysis in vitro and evaluated the contribution of platelets to this process.

MATERIALS AND METHODS

Non-anticoagulated blood was mixed with CM or saline (50% or 20% (v/v)) for 1 min then citrated. Thrombi were produced in vitro under flow in a Chandler loop. Thrombus structure was visualized by immunohistochemistry using FITC-fibrin/ogen antibodies, and propidium iodide to identify nucleated blood cells. To measure fibrino/thrombolysis release of FITC-labeled fibrinogen, added prior to thrombus formation, was measured over 24 h. Platelet degranulation was analyzed by whole blood flow-cytometry.

RESULTS

No thrombi formed from blood incubated with Ioxaglate. Thrombi formed with Iohexol or Iodixanol weighed > OR = 10x more than saline controls (116+/-52 and 230+/-128 mg vs. 11+/-3 mg, respectively; p<0.0005), and were more resistant to thrombolysis as evidenced by the release of FITC over 24 h (19.1+/-8.9 and 31.9+/-17.2 U vs. 65.1+/-19.1 U, respectively; p<0.02). Thrombi formed with Iodixanol and Iohexol had larger, more diffuse platelet-rich head areas and tail regions composed of a more open fibrinogen/fibrin meshwork enclosing denser RBC rich areas compared to controls. Iodixanol and Ioxaglate did not increase platelet degranulation, but Iohexol caused a significant increase compared to the saline control (percentage of platelets expressing P-selectin 68.9+/-23.43% vs. 4.93+/-1.44%, respectively; p=0.001).

CONCLUSION

Thus thrombi formed with Iodixanol or Iohexol will be larger and more resistant to thrombolysis, whereas Ioxaglate may reduce the risk of thrombus formation.

Prophylaxis of Iodinated Contrast Media-Induced Nephropathy

Iodinated contrast media are a frequent cause of acute renal failure, especially in patients whose renal function is already impaired. In addition to hydration, which remains the most commonly acknowledged means of protection, numerous pharmacological approaches for the prophylaxis of contrast nephropathy have been tested so far. They include diuretics, calcium channel blockers, adenosine receptor antagonists, N-acetylcysteine, low-dose dopamine and the dopamine D1 receptor agonist fenoldopam, endothelin receptor antagonists, and even captopril. The present review of the literature critically discusses the drugs used to prevent contrast nephropathy from a pharmacological point of view.

Effects of hyperosmolar ionic and low osmolar non-ionic contrast media on coagulation times and some blood parameters in dogs: an in vivo study

The purpose of this study is to evaluate the effects of hyperosmolar ionic contrast media (CM) (diatrizoate) and low osmolar non-ionic CM (iohexol and ioxilan) on coagulation time and some blood parameters in dogs in vivo. The animals were divided into three groups in equal numbers. The dogs in groups I, II and III received diatrizoate, iohexol and ioxilan at the dose of 700 mgI/kg intravenously (IV) as a bolus, respectively. Administration of contrast media and blood samples were collected from vena cephalica antebrachii prior to CM administration and thereafter at 3, 15, 30, 60, 90 and 180 min and 24 h to measure the coagulation factors [activated partial thromboplastin time (APTT), prothorombin time (PT), fibrinogen and fibrinogen degradation products] and some other blood parameters [red blood cells, platelet, white blood cells, haematocrit (Ht) and haemoglobin (Hb)]. While a statistically significant decrease was observed on APTT at 15 min in group III, no significant differences were found in groups I and II. All the groups had insignificant alterations for PT, fibrinogen and fibrinogen degradation product, following CM administration. Significant decreases were observed for platelet at 3 min in all groups. This decrease was also significant at 15- and 30- min intervals in group I. There were significant decreases for erythrocytes, Ht and Hb measurements within 30 min, and no significant alterations were observed for leucocytes within 60 min in all groups compared with baseline values. No differences were observed with regard to coagulation times and some blood parameters as far as long-lasting and major effects of each CM are concerned.

Results of the safety and efficacy of iobitridol in more than 61,000 patients

We present results of a postmarketing surveillance study with iobitridol (Xenetix, Sulzbach, Germany) in more than 61,000 patients from 1996 until 2000. The purpose of this study was the assessment of safety and diagnostic efficacy of the non-ionic contrast agent iobitridol in the setting of a post-marketing surveillance study. Iobitridol (Xenetix) has been registered in Germany since 1996. Between 1996 and 2000 207 radiologists have documented in a questionnaire the routine use of Xenetix in 61,754 patients that have received Xenetix for diagnostic procedures. On each questionnaire parameters regarding demographic data, safety, and diagnostic efficacy were assessed. The data were statistically evaluated and analysed. The examination allowed for a diagnosis in 99% of cases. Image quality was rated as "excellent" or "good" in 89.8% of cases. In obese patients there was a significantly higher percentage ( p<0.001) of poor image quality. In 0.1% poor contrast was noted. Of patients, 28.8% had at least one risk factor, and 3.1% had three or more. Adverse events were noted in 2.3% of the examinations, but nearly half of them (1.1%) presented with "feeling of warmth" as the only symptom. Of adverse events, 0.2% were non-transient, and 1 patient died. In 0.2% of patients the procedure was stopped due to adverse events. In 0.9% of patients the causal relationship with the contrast agent was rated as probable (probable+possible=1.1%). The percentage of adverse events (excluding warmth) was independent of iodine concentration and of dose, and was higher in young patients. Xenetix is an efficient contrast agent for radiological procedures and is associated with a low rate of adverse events.

Comparative tolerability of contrast media used for coronary interventions

Radiographic contrast media (CM) are necessary to provide x-ray absorption of the bloodstream; all other observed effects need to be regarded as adverse. Four types of CM are currently used in diagnostic and interventional cardiology: ionic high-osmolar CM (HOCM), either ionic or non-ionic low-osmolar CM (LOCM), and non-ionic iso-osmolar CM (IOCM). Focusing on the potential cardiovascular effects caused by the CM, there is a clear difference between HOCM and the LOCM or IOCM. HOCM have a poorer profile due to a higher incidence of hypotension and electrophysiological effects. To prevent contrast-induced nephropathy, HOCM should be avoided and patients should receive the minimal dose of LOCM or IOCM with intravenous hydration before and after the procedure. Clinical hyperthyroidism has been detected after CM use, but the condition appears, ultimately, to be self-limited and to occur mainly in elderly patients. When assessing the need for a CM in terms of improved patient safety, preventing serious complications should be the major factor determining the choice. CM should not be selected on the basis of minor adverse effects since these are, ultimately, of low clinical relevance. Thrombotic events, in contrast, carry a high clinical relevance and we consider that these should be the main issue governing current choice. Ionic LOCM appear to have better profile than other CM with respect to interaction with platelet function and coagulation. In relation to thrombotic events in randomised clinical studies, ionic CM have been associated, mainly, with favourable and some neutral results compared with non-ionic agents. Only one trial indicated a more pronounced antithrombotic effect of the non-ionic IOCM relative to the ionic LOCM. The antithrombotic advantages of ionic over non-ionic LOCM are, in part, balanced by a greater frequency of minor adverse effects such as nausea, vomiting or cutaneous rashes. A matter of concern is the delayed adverse effects observed with non-ionic IOCM. However, severe and life-threatening reactions are exceptional and there are probably no significant differences between IOCM and LOCM whether ionic or non-ionic. However, in patients with known allergies, non-ionic CM are to be recommended. On the basis of the available pre-clinical and clinical data, the ionic LOCM or the non-ionic IOCM are the agents to be recommended in percutaneous coronary interventions because of their antithrombotic advantages over non-ionic LOCM.

Roles of intracellular Ca2+ and cyclic AMP in mast cell histamine release induced by radiographic contrast media

Mast cell histamine release is considered to be associated with the etiology of anaphylactoid reactions to iodinated radiographic contrast media (RCM). In the present study, the effects of various ionic and non-ionic RCM on histamine release from mast cells were compared, and the possible mechanisms of the histamine release were subsequently determined. Both ionic (ioxaglate and amidotrizoate) and non-ionic (iohexol, ioversol, iomeprol, iopamidol and iotrolan) RCM increased histamine release from the dissociated rat pulmonary cells, whereby ionic materials were more potent than non-ionic agents. There was no significant correlation between the extent of histamine release and the osmolarity of each RCM solution. In addition, hyperosmotic mannitol solution (1000 mOsm/kg) caused no marked histamine release. Thus, it is unlikely that the hyperosmolarity of RCM solutions contributes to the histamine release. RCM also stimulated, but to a lesser extent, the histamine release from rat peritoneal cells. The RCM-induced histamine release from both types of cells was inhibited by dibutyl cyclic AMP or combined treatment with forskolin and 3-isobutyl-1-methylxanthine. Corresponding to these results, RCM markedly reduced the cellular cyclic AMP content. On the other hand, the removal of intracellular but not the extracellular Ca2+ attenuated the RCM-induced mast cell histamine release. From these findings, it is suggested that the decrease in cellular cyclic AMP content and an increase in intracellular Ca2+ contribute at least in part to the RCM-induced mast cell histamine release.

The ionic contrast medium ioxaglate interferes with thrombin-mediated feedback activation of factor V, factor VIII and platelets

Clinical observation shows that radiographic contrast media (CM) may influence thrombus formation. In the search for the underlying mechanism, we have shown that the ionic CM ioxaglate is a potent inhibitor of thrombin generation in platelet-poor and platelet-rich plasma, whereas the influence of the non-ionic contrast medium iodixanol is minimal. Ioxaglate boosts the inhibitory effect of the platelet GPIIb/IIIa antagonist abciximab and the effects of ioxaglate and heparin are additive. Ioxaglate inhibits the clotting of fibrinogen and the activation of factors V and VIII, and of platelets by thrombin. It does not inhibit hydrolysis of small chromogenic thrombin substrates, nor does it influence the heparin-catalyzed inactivation of thrombin by antithrombin. We assume therefore that ioxaglate interferes with the binding of macromolecular substrates to the anionic exosite I of thrombin. The biological correlation to the observed antithrombotic effect of ioxaglate is then to be found in the inhibition of thrombin generation via inhibition of thrombin-mediated feedback activations.

In vivo comparative antithrombotic effects of ioxaglate and iohexol and interaction with the platelet antiaggregant clopidogrel

RATIONALE AND OBJECTIVES

Experiments were designed to (1) compare the effects of iodinated contrast media (CM) on a rat model of arterial thrombosis, (2) evaluate which element of the ioxaglate solution supports its antithrombotic activity, and (3) investigate the interaction of ionic and non-ionic CM with the antiplatelet agent clopidogrel.

MATERIALS AND METHODS

Carotid thrombosis was induced in rats by extravascular application of a filter paper soaked in FeCl3 (35% vol/wt), proximal to an ultrasonic flow probe. (1) The antithrombotic potential of low-osmolar ionic (ioxaglate Na/meglumine) or nonionic contrast media (iohexol and iodixanol) (all 1600 mg iodine/kg, IV) was assessed by measuring the time to occlusion (TTO) of the carotid artery and the thrombus weight (TW). (2) Isotonic saline and iso-osmolar (280 mOsm/kg) and hyperosmolar (560 mOsm/kg) solutions of meglumine hydrochloride, meglumine ioxaglate (560 mOsm/kg), sodium ioxaglate (600 mOsm/kg) and sodium and meglumine ioxaglate (commercial solution) were tested under similar conditions. (3) Interaction with clopidogrel was tested by injecting lower dose of CM (960 mg iodine/kg) 2 hours after clopidogrel (2 mg/kg per os).

RESULTS

(1) Ioxaglate prolonged TTO when compared with saline (30.0 +/- 1.1 minute vs. 19.6 +/- 2.4 minutes, P< 0.001), whereas iohexol had no effect (21.3 +/- 1.3 minutes). Ioxaglate's effect was associated with a reduction in TW with ioxaglate versus saline (2.6 +/- 0.4 mg and 4.7 +/- 0.7 mg, respectively, P< 0.05) whereas TW remained unchanged in the iohexol group (4.2 +/- 0.4 mg). The nonionic dimer iodixanol induced a direct vasoconstrictor effect on the carotid artery and was consequently excluded from the study. (2) Neither iso-osmolar nor hyperosmolar solutions of meglumine had any effect on TTO whereas both sodium and meglumine salts of ioxaglic acid prolonged TTO, suggesting that the antithrombotic effect of ioxaglate is mediated by the ioxaglic acid moiety alone as neither meglumine, osmolality or sodium played a significant role. (3) A synergistic effect on TTO was found when ioxaglate was associated with clopidogrel whereas no such effect was observed with iohexol.

CONCLUSIONS

These data show a greater in vivo antithrombotic potential for the ionic contrast medium ioxaglate than for the non-ionic contrast medium iohexol and, for the first time, a synergistic effect between a contrast medium and a platelet antiaggregant drug in vivo.

Effects of two dimeric iodinated contrast media on renal medullary blood perfusion and oxygenation in dogs

RATIONALE AND OBJECTIVES

To compare the effects of two iodinated contrast media, iodixanol and ioxaglate, on outer medullary blood flow (MBF) and oxygen tension (MPO(2)) in the dog kidney.

METHODS

Iodixanol and ioxaglate were injected selectively into the renal artery (320 mgI/kg) of anesthetized Beagle dogs. MBF and MPO(2) were measured with a laser-Doppler probe and an oxygen-sensing microelectrode implanted in the outer medulla. Urine samples were collected for viscosity and osmolality measurements.

RESULTS

Both contrast media produced a moderate decrease in MBF and MPO(2). The hypoperfusion and hypoxia lasted significantly longer with iodixanol than with ioxaglate. Theophylline, an adenosine receptor antagonist, partially prevented iodixanol-induced hypoxia. Urine viscosity was dramatically increased by iodixanol but not by ioxaglate. Urine osmolality did not differ significantly between groups.

CONCLUSION

Iodixanol produced a more sustained medullary hypoxia than ioxaglate when injected selectively into the dog renal artery. This may lead to hypoxic cellular damage and subsequent impairment of kidney functions.

CT pulmonary angiography with a macromolecular contrast medium: a comparative study versus iobitridol in rabbits

RATIONALE AND OBJECTIVES

To compare the pharmacokinetics of a new macromolecular iodinated contrast medium, prototype P743, with a standard contrast agent (iobitridol) for spiral computed tomography pulmonary angiography in rabbits.

METHODS

Manual injection was first used to test the performance of P743 even in cases of nonoptimal bolus timing. Then a protocol was designed to compare vessel enhancement in both first-pass and delayed scans for the two contrast agents with the help of a power injector.

RESULTS

With manual fast injection, the first pass of iobitridol was observed only on proximal scans. Conversely, opacification of vessels was maintained during three spiral scans with P743 under the same injection conditions. When optimal bolus timing was performed, higher vessel enhancement was observed during bolus first pass with iobitridol (iodine dosage 250 mg I/kg) compared with P743 (150 mg I/kg). However, during the postbolus phase, the decrease in attenuation values was markedly faster with iobitridol than with P743.

CONCLUSIONS

This study confirmed that P743 remains more intravascular than iobitridol, which may have clinical implications for the diagnosis of pulmonary embolism, for example.

Changes in endothelial, leucocyte and platelet markers following contrast medium injection during angiography in patients with peripheral artery disease

Peripheral artery angiography, a common diagnostic procedure, may cause early and late adverse reactions, such as anaphylaxis, thrombosis and possible progression of the underlying arterial disease. To test the hypothesis that radiographic contrast medium may contribute to these events by adversely affecting the endothelium, leucocytes and/or platelets, 19 subjects undergoing angiography for the investigation and/or treatment of lower limb atherosclerosis were recruited. Blood was obtained from the external iliac vein before, and at serial intervals after, the injection of radiographic contrast medium into the ipsilateral femoral artery for diagnostic use. Markers of endothelial cell injury (von Willebrand factor (vWf)), platelet activation (soluble P-selectin) and leucocyte activation (neutrophil elastase and soluble L-selectin) were measured in citrated plasma. Soluble intercellular adhesion molecule-1 (sICAM-1) and thromboxane B(2), which are non-specific markers of inflammation, were also measured. Compared with the sample prior to angiography, levels of soluble L-selectin and sICAM-1 were reduced (p<0.02) immediately after passage of the last bolus of contrast medium. 15 min later, levels returned to normal but the level of vWf had increased (p<0.02). After 30 min, only levels of thromboxane B(2) were increased (p<0.05). The following day both vWf (p<0.01) and soluble P-selectin (p<0.05) were increased. These data point to both early and late effects of contrast medium on markers of endothelial, platelet and leucocyte function.

Comparative effects of ionic and nonionic iodinated low-osmolar contrast media on platelet function with the PFA-100 (platelet function analyzer)

RATIONALE AND OBJECTIVES

This study was designed to (1) compare the effects of ionic (ioxaglate) and nonionic (iodixanol and iohexol) iodinated low-osmolar contrast media (CM) on platelet function in human whole blood by using the new PFA-100trade mark, a "platelet function analyzer"; (2) determine the animal species closest to human with regard to platelet reactivity to CM; and (3) evaluate which element of the ioxaglate solution supports this activity.

METHODS

For all studies, platelet adhesion and aggregation were measured using the PFA-100trade mark system with adenosine diphosphate-primed collagen membrane cartridges. Results are shown as the membrane closure time (MCT; the longer the MCT, the greater the antiaggregatory effect) and given as medians. Citrated whole-blood samples from six healthy volunteers were mixed for 1 minute with a 10% (vol/vol) solution of ioxaglate, iodixanol, or iohexol or their respective ionic and nonionic controls (isotonic saline and mannitol). The test solution/control solution ratio for the MCT was calculated for the blood of humans, guinea pigs, rabbits, dogs, and rats. Isotonic saline and iso-osmolar (280 mOsm/kg) and hyperosmolar (560 mOsm/kg) solutions of meglumine hydrochloride, meglumine ioxaglate (560 mOsm/kg), and sodium ioxaglate (600 mOsm/kg) were tested under similar conditions.

RESULTS

All three CM caused significant prolongation of MCT when compared with their respective controls (ioxaglate: 300 seconds, ie, "no closure" on the PFA-100trade mark system; iodixanol: 179 seconds; iohexol: 171 seconds; saline: 115 seconds; mannitol: 118 seconds). The antiplatelet effect of ioxaglate was higher than that of iodixanol and iohexol (P < 0.05). The animal species tested did not differ significantly from the human species with regard to an effect of their blood on MCT. Both ioxaglic acid salts caused a higher prolongation of MCT when compared with saline (sodium salt: 259 seconds; meglumine salt: 212 seconds; P < 0.05 vs. saline) but not versus the ioxaglate commercial solution. Conversely, both iso- and hyperosmolar solutions of meglumine hydrochloride (108 and 128 seconds, respectively) did not lengthen MCT versus saline, but their MCTs were shorter than that of the commercial solution of ioxaglate (P < 0.05).

CONCLUSIONS

The ionic CM ioxaglate displayed a greater antiaggregatory effect on human platelets than did both iso-osmolar (iodixanol) and hyperosmolar (iohexol) nonionic CM. This effect seems to be linked to the ioxaglic moiety, because neither osmolality nor sodium or meglumine appeared to play a significant role.

Preclinical profile of the monodisperse iodinated macromolecular blood pool agent P743

RATIONALE AND OBJECTIVES

To summarize the chemical synthesis, physicochemical characterization, pharmacokinetic behavior, and biological evaluation of P743, a new macromolecular iodinated contrast medium.

METHODS

The synthesis and molecular modeling of the iodinated macromolecule P743 are described. The pharmacokinetic profile was established in rabbits and rats. Acute toxicity in mice, renal tolerance in normal rabbits, and renal tolerance in uninephrectomized, dehydrated rats undergoing selective intrarenal injection was evaluated. In vitro permeability effects on isolated mastocytes and on the coagulation pathways were carried out. Computed tomography vascular imaging was performed after intravenous injection of P743 (300 mg I/kg) in rabbits and compared with the nonspecific nonionic agent iobitridol.

RESULTS

P743 is a monodisperse, macromolecular iodinated contrast medium. In both rabbits and rats, P743 showed a pharmacokinetic profile consistent with that of a rapid-clearance blood-pool agent. Its diffusion through the endothelium was found to be low in vitro, thus confirming early confinement of this macromolecule, unlike nonspecific contrast media. In both species, P743 was excreted by glomerular filtration. Acute toxicity disclosed no mortality at the highest volume that could be injected into mice, leading to a median lethal dose greater than 8.9 g I/kg. Renal tolerance was found to be good in both euvolemic rabbits and uninephrectomized, dehydrated rats. No histamine or leukotriene B4 release was found on RBL-2H3 isolated mastocytes. P743 did not interfere with the coagulation pathways. Imaging experiments confirmed that P743 remains in the vascular compartment for a longer time than does iobitridol, thus allowing vascular enhancement that is twice as high as that of iobitridol in the recirculation phase.

CONCLUSIONS

The pharmacokinetic and imaging profiles of P743, a new, monodisperse, macromolecular blood-pool iodinated contrast medium, were consistent with those of a rapid-clearance blood-pool agent. Its initial safety profile is satisfactory. Further experimental imaging studies are required to define the clinical interest in such molecules.

Thrombotic risk associated with the use of iodinated contrast media in interventional cardiology: pathophysiology and clinical aspects

A review of the current knowledge of the anti-thrombotic properties of iodinated contrast media (CM) has been conducted. CM are classified according to their chemical structure, either ionic or non-ionic (monomeric or dimeric). Numerous in vitro and in vivo data show that, although all CM have anti-coagulant properties, ionic molecules are more potent than non-ionic and, furthermore, do not activate resting platelets, unlike non-ionic agents. These properties may lead to a decrease in thrombus formation during interventional procedures. Several clinical trials have shown that CM may play a role in the occurrence of acute thrombotic complications but also in delayed ischaemic events during interventional procedures. A recent meta-analysis showed that, compared to non-ionic monomers, ionic low-osmolar CM reduce the rate of coronary artery abrupt closure, but no significant difference was found with respect to ischaemic complications. Ionic CM lead to a lower deposit of thrombotic materials on catheters and guide-wires. To date, clinical data comparing ionic CM and non-ionic dimers are scarce, significantly heterogeneous and, unlike experimental data, they do not show differences between both classes of CM. Further studies are required to better understand the precise mechanisms of such interactions and to analyse the effect of CM when new antiplatelet agents or new procedures (stenting) are used, to comply with new clinical strategies.