Impact of anticoagulation on ionic and nonionic contrast media effect on thrombogenesis and fibrinolysis: The PEPCIT study

Spontaneous obliteration of a spinal perimedullary fistula

We herewith report a young patient who had an incidental spinal vascular malformation of the cervicomedullary junction discovered during a work-up for anosmia. Angiography demonstrated a perimedullary spinal arteriovenous fistula with supply from lateral spinal arteries arising from bilateral V3 level segmental arteries. It was decided to manage the patient conservatively with magnetic resonance imaging monitored biannually. On a recent follow-up magnetic resonance, nearly 10 years later, we noted a subtle change in caliber and imaging characteristics at the posterior margin of the cervical medullary junction. Repeat digital-subtraction angiography showed no evidence of early venous filling from the previously involved branches. Microcatheter exploration of the right lateral spinal artery confirmed spontaneous occlusion of the spinal perimedullary arteriovenous fistula, without any persistent shunting. Spontaneous resolution of a spinal vascular malformation is rare; this case demonstrates the dynamic nature of shunting vascular malformations and that spontaneous obliteration of arteriovenous shunts is possible.

Spinal vascular malformations: Angiographic evaluation and endovascular management

Spinal vascular malformations (SVM) are classified based on their location (intramedullary, perimedullary, radicular, extradural) and flow pattern (high-flow, low-flow, no arteriovenous shunt). High-flow SVMs are generally congenital lesions diagnosed in children and young patients without gender predominance. They present with hemodynamic disturbances, mass effect, or hemorrhages, but may also be discovered incidentally. Low-flow SVMs tend to be acquired lesions presenting in older men with progressive myelopathy caused by spinal venous hypertension. They are rarely associated with vascular syndromes but may accompany prothrombotic conditions. The sensitivity and specificity of conventional MRI are excellent for high-flow SVMs but poor for low-flow lesions, which are frequently diagnosed with extensive delays reducing the potential for favorable outcomes. The sensitivity of advanced MRI techniques remains unclear, notably for the detection of low-flow shunts without flow voids on conventional MRI. Catheter angiography remains the gold standard modality for the evaluation of the spinal vasculature and its disorders. SVMs can be treated by surgical or endovascular means. Initially plagued by high recurrence rates due to inadequate embolization material, endovascular techniques represent nowadays a valid alternative to surgery, thanks notably to the introduction of liquid embolic agents.

In vitro analysis of the effect of contrast agents on the antiaggregant effects of P2Y12 inhibitors

OBJECTIVES

The contrast agents have different molarities and ionic structures. The high osmolar contrast agents could increase platelet aggregation but the ionic contrast agents decrease platelet aggregation. However there is insufficient data on whether the antiaggregan effect of P2Y12 inhibitors used during coronary interventions are affected by the contrast agents. This study aimed to evaluate the in vitro effects of different contrast agents on the antiaggregant activity of P2Y12 inhibitors (clopidogrel, ticagrelor and prasugrel).

MATERIALS AND METHODS

Thirty patients (who underwent percutaneous coronary interventions and were treated with a P2Y12 inhibitor for a minimum of 10 days) and five healthy volunteers were divided into four groups: the clopidogrel (10 patients), ticagrelor (10 patients), prasugrel (10 patients) and control (five volunteers) groups. Antiaggregant activity was measured by using the Verify-Now method and was represented as P2Y12 reaction unit (PRU) values. Three tubes of blood were collected from the participants in the three patient groups and in the control group; as the contrast material, 10% iohexol was added to a second tube, and 10% iodixanol was added to a third tube. PRU values of the control and the contrast tubes were measured at 5 min and at 30 min after the contrast material was added.

RESULTS

Iohexol and iodixanol led to a significant decrease in the PRU values in the control group (iohexol: 188.4 ± 39.2 vs 142.4 ± 17.0, p = .04; iodixanol: 188.4 ± 39.2 vs 159.2 ± 33.7, p = .04) and in the clopidogrel group (iohexol: 140.8 ± 50.8 vs 106.3 ± 44.4, p = .04; iodixanol: 140.8 ± 50.8 vs 109.4 ± 47.6, p = .009) but not in the ticagrelor and prasugrel groups. The PRU values were significantly lower in the ticagrelor (23.1 ± 26.2) and prasugrel (23.4 ± 27.5) groups than in the clopidogrel (140.8 ± 50.8) and control (188.4 ± 39.2) groups (p < .01), and the PRU values for the ticagrelor and prasugrel groups were similar for both the 5-min and 30-min time periods (p > .05). The antiaggregant activities of iohexol and iodixanol were observed to be similar at the 5- and 30-minute time points for all of the groups (p > .05).

CONCLUSION

Iohexol and iodixanol had in vitro antiaggregant effects, and their antiaggregant effects were similar. Iohexol and iodixanol increased the clopidogrel antiaggregant activity in vitro, but they did not significantly alter the antiaggregant activities of prasugrel and ticagrelor.

Validation of myocardial perfusion quantification by dynamic CT in an ex-vivo porcine heart model

To test the accuracy of quantification of myocardial perfusion imaging (MPI) using computed tomography (CT) in ex-vivo porcine models. Five isolated porcine hearts were perfused according to Langendorff. Hearts were perfused using retrograde flow through the aorta and blood flow, blood pressure and heart rate were monitored throughout the experiment. An inflatable cuff was placed around the circumflex (Cx) artery to create stenosis grades which were monitored using a pressure wire, analysing perfusion at several fractional flow reserve values of 1.0, 0.7, 0.5, 0.3, and total occlusion. Second-generation dual-source CT was used to acquire dynamic MPI in shuttle mode with 350 mAs/rot at 100 kVp. CT MPI was performed using VPCT myocardium software, calculating myocardial blood flow (MBF, ml/100 ml/min) for segments perfused by Cx artery and non-Cx myocardial segments. Microspheres were successfully infused at three stenosis grades in three of the five hearts. Heart rate ranged from 75 to 134 beats per minute. Arterial blood flow ranged from 0.5 to 1.4 l min and blood pressure ranged from 54 to 107 mmHg. MBF was determined in 400 myocardial segments of which 115 were classified as ‘Cx-territory’. MBF was significantly different between non-Cx and Cx segments at stenosis grades with an FFR ≤0.70 (Mann–Whitney U test, p < 0.05). MBF showed a moderate correlation with microsphere MBF for the three individual hearts (Pearson correlation 0.62–0.76, p < 0.01). CT MPI can be used to determine regional differences in myocardial perfusion parameters, based on severity of coronary stenosis. Significant differences in MBF could be measured between non-ischemic and ischemic segments.

Iodixanol as a Contrast Agent in a Fibrin Hydrogel for Endodontic Applications

The application of biomaterials used in regenerative endodontics should be traceable. In this study, we checked some basic effects of rendering a fibrin hydrogel radiopaque using an iodine-based contrast agent (iodixanol) approved for systemic application. Fibrin hydrogels were prepared from a fibrin sealant (Tisseel) using either an isotonic iodixanol solution (Visipaque 320, test) or Tris buffer (control) as a diluent. Gelation kinetics, radiopacity, and swelling of lyophilized hydrogels were tested using standard methods. Hydrogel structure was evaluated using scanning electron microscopy (SEM). Furthermore, iodixanol release from the test gels was assessed using spectrophotometry, and tissue compatibility was compared between test and control hydrogels using the chick chorioallantoic membrane (CAM) assay. Results were compared using pairwise t-test, p < 0.05. Iodixanol caused a 70-fold delay in gelation to 26 min in the test compared to the control hydrogels (22 ± 1 s). Radiopacity of the test gels was 1.9 ± 0.2 mm Al/mm, compared to zero in the control hydrogels. Lyophilized hydrogel swelling was strongly reduced when iodixanol was added to the hydrogel (p < 0.05). Test hydrogels had an altered SEM appearance compared to controls, and exhibited a reduced porosity. Iodixanol release from the test hydrogels reached 14.5 ± 0.5% after 120 h and then ceased. This release did not have any apparent toxic effect and neither affected the viability, nor the physiology or vascularization of the CAM of fertilized chicken eggs. Iodixanol can render a fibrin hydrogel radiopaque and maintains its tissue compatibility, yet impacts gelation kinetics and hydrogel porosity.

The assessment of thrombotic markers utilizing ionic versus non-ionic contrast during coronary angiography and intervention trial

OBJECTIVE

To determine how two different types of iodinated contrast media (CM), low-osmolar ionic dimer ioxaglate (Hexabrix) and iso-osmolar non-ionic dimer iodixanol (Visipaque), affect multiple indices of hemostasis.

BACKGROUND

In vitro models demonstrate differential effects of ionic and non-ionic CM on markers of hemostasis.

METHODS

This blinded endpoint trial randomized 100 patients to ioxaglate or iodixanol. The primary endpoint was change in endogenous thrombin potential (ETP) following diagnostic angiography. Secondary endpoints included change in markers of fibrinolysis [tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1)] and platelet aggregation following diagnostic angiography and percutaneous coronary intervention (PCI) with bivalirudin. Data are presented as median [interquartile range].

RESULTS

ETP significantly decreased after diagnostic angiography in both ioxaglate (baseline 1810 nM*minute [1540-2089] to post-angiography 649 nM*minute [314-1347], p < 0.001) and iodixanol groups (baseline 1682 nM*minute [1534-2147] to post-angiography 681 nM*minute [229-1237], p < 0.001), but the decrease was not different between CM (p = 0.70). There was a significant increase in ETP during PCI (n = 45), despite the use of bivalirudin, suggesting a prothrombotic effect of PCI (post-angiography 764 nM*minute [286-1283] to post-PCI 1081 nM*minute [668-1552], p = 0.02). There were no significant differential effects on tPA, PAI-1, and markers of platelet activity.

CONCLUSION

There were no significant differential effects between ioxaglate and iodixanol. Both CM led to significant reductions in thrombin generation and no significant effects on fibrinolytic activity or platelet activity, thereby contributing to a favorable antithrombotic milieu. © 2016 Wiley Periodicals, Inc.

Contrast media: are there differences in nephrotoxicity among contrast media?

Iodinated contrast agents are usually classified based upon their osmolality--high, low, and isosmolar. Iodinated contrast agents are also nephrotoxic in some but not all patients resulting in loss of glomerular filtration rate. Over the past 30 years, nephrotoxicity has been linked to osmolality although the precise mechanism underlying such a link has been elusive. Improvements in our understanding of the pathogenesis of nephrotoxicity and prospective randomized clinical trials have attempted to further explore the relationship between osmolality and nephrotoxicity. In this review, the basis for our current understanding that there are little if any differences in nephrotoxic potential between low and isosmolar contrast media will be detailed using data from clinical studies.