Relationship of anticoagulation and radiographic contrast agents to thrombosis during coronary angiography and angioplasty: are there real concerns?

Angioplasty with Stenting in Acute Coronary Syndromes with Very Low Contrast Volume Using 6F Diagnostic Catheters and Bench Testing of Catheters

AIM

To safely perform angioplasties in acute coronary syndromes with low contrast volume using Cordis 6F diagnostic catheters and to perform mechanical bench tests on the diagnostic and guide catheters in a radial path model.

METHODS

In 191 patients (242 lesions/268 stents) with acute coronary syndromes angioplasty were performed with cordis 6F diagnostic catheters.

RESULTS

The lesions were present at left anterior descending (121), Left main (5), left circumflex (51), ramus (5) and right coronary artery (60). In 72% of cases, Iodixanol was used. All contrast injections were given by hand. Regular follow-up of the patients was performed at 30 days. The procedures were performed in the femoral route only. Pre-dilatation was performed in 43 cases. Successful revascularization of the target lesion was achieved in all cases. The mean contrast volume used per patient was 28 ml (± 8 ml). Mild reversible contrast-induced nephropathy (CIN) was observed in two patients. Cardiogenic shock was seen in 7 cases, and one death was observed. Pushability and trackability tests showed good force transmission and hysteresis in diagnostic catheters compared to guide catheters.

CONCLUSIONS

Angioplasty with stenting could be performed safely in patients using cordis 6F diagnostic catheters using a low volume of contrast in acute coronary syndromes. Low contrast volume usage would result in a lower incidence of contrast-induced nephropathy and cardiac failures.

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.

Influence of ionic and non-ionic radiographic contrast media on leukocyte adhesion molecules

BACKGROUND: Many papers have focused on the importance of granulocytes in the process of reperfusion and ischemia. Most of the clinical studies measured several parameters of this process during and after coronary angiography, without taking into account the effect of the radiographic contrast media (RCM) used during this procedure. MATERIALS AND METHODS: We performed a randomized patient study (n = 37) to evaluate the effect of ionic and non-ionic RCM on granulocyte adhesion during coronary angiography. We also evaluated the influence of the ionicity and osmolarity of the different substances on granulocyte adhesion molecules in in vitro experiments. RESULTS: The osmolarity of patient serum samples increased from 302 +/- 1 to 309 +/- 1 mOsm/kg (p < 0.05) after infusion of RCM. The CD11b expression in the samples of the non-ionic RCM treated group increased from 221 +/- 21 MFI to 377 +/- 30 MFI (p < 0.05) measured as the absolute mean fluorescence intensity (MFI), yet did not alter significantly in the ionic RCM group. In contrast, the in vitro experiments showed a reduction of the CD11b expression from 360 +/- 70 MFI to 149 +/- 30 MFI (p < 0.05) in the ionic RCM group. CONCLUSIONS: The upregulation of adhesion molecules was significantly reduced in vivo with ionic RCM, while ionic substances caused opposite effects in vitro. This effect should be taken into account when performing leukocyte functional analysis of samples taken during angiography.

Effect of prolonged blood contact time on deposition of cellular and amorphous material on teflon-coated guidewires: a scanning electron microscopy study

Prolonged contact of blood with guidewires and catheters has been implicated in leading to thromboembolic complications during cardiac catheterization. To study the effect of exposure time on blood product deposition on Teflon-coated guidewires, 35 patients undergoing routine coronary arteriography were randomly assigned to three time groups with exposure of the guidewire to blood of 3, 5, and 10 min, respectively. The exposed wires were examined by scanning electron microscopy, and the micrographs were graded by a pathologist "blinded" as to the exposure time. Deposition of cellular and amorphous material on the guidewire surface and interstices was graded using an arbitrary scale of 1-10 (1, least amount; 10, abundant amount of material). All patients received low-dose systemic administration of heparin (2,500 units) at the beginning of the procedure. The overall activated clotting time (ACT) was 147 +/- 39 sec (mean +/- SD) prior to heparin dose. The mean ACT after low-dose systemic heparin, measured at sheath removal immediately after exposure of the wire to blood had been completed, rose to 241 +/- 79 sec (P < 0.0001). The deposition of cellular and amorphous material on the surface and grooves of the wire was not significantly different at 3, 5, and 10 min. Thus, in this study, Teflon-coated guidewires showed no increase in cellular or amorphous deposits from 3 min to 10 min of blood-wire contact time in the presence of low-dose heparinization.

Factors influencing the activation of platelets by nonionic contrast medium

PURPOSE

To determine why nonionic, low-osmolality contrast media (LOCM) at high concentrations (> 30%) induce almost immediate platelet activation and to explore preventive measures.

MATERIALS AND METHODS

Nonionic LOCM, when added to blood, activates platelets, raises the osmolality, and lowers the ionic strength. To clarify the mechanisms involved, platelet activation was studied in sodium chloride-sucrose solutions of varying osmolalities and varying ionic strengths. Several salts and Iloprost were evaluated as potential inhibitors of platelet activation.

RESULTS

Platelets are activated by both osmolality and ionic strength changes. The salts most inhibitory to platelet activation were magnesium sulfate and sodium citrate. Iloprost lowered platelet activation to control levels at 4.3 ng/mL of nonionic LOCM and completely eliminated it at 8.6 ng/mL.

CONCLUSION

Three-quarters of nonionic LOCM-induced platelet activation appeared to be due to increased osmolality-the remainder to the decrease in ionic strength. Magnesium sulfate and Iloprost are potent inhibitors of this type of platelet activation.

Iohexol vs. ioxaglate in lower extremity angiography: a comparative randomized double-blind study in 80 patients

The aim of this study was to detect clinically relevant differences between iohexol 300 mgI/ml and ioxaglate 320 mgI/ml in lower extremity arteriography. In this randomized double-blind study, 40 patients were examined with iohexol and 40 patients with ioxaglate. Adverse events were evaluated by recording the time of onset and the duration of possible adverse events: during or immediately following the contrast medium injections, after 6 h, and after 24 h following these injections. Heat and pain were scored on visual analog scales. The amount of contrast medium and possible thromboembolic complications were noted. Image quality was evaluated. There were no significant differences in the total amounts of contrast agent administered (ioxaglate mean 121.5 ml vs. iohexol 125.1 ml), scores for heat (ioxaglate mean 6.1 vs. iohexol 6.1) and pain (both agents mean 2.35). Nausea/vomiting was noticed significantly more frequently with ioxaglate (ioxaglate seven patients vs. iohexol one patient (chi 2, P < 0.05)). Thromboembolic complications were not detected. Opacification of vessels was optimal in all patients. No clues were found indicating that one of the agents was better tolerated 6-24 h after the procedure than the other. Nausea/vomiting occurred significantly more frequent with ioxaglate; no further clinically relevant differences were detected.

Effect of contrast media on in vitro bleeding time: assessment by a hollow fiber instrument

RATIONALE AND OBJECTIVES

We used a global screening device that operates under physiologic flow conditions to monitor the effects of ionic and nonionic contrast media (CM) on hemostasis.

METHODS

This flow dynamic technique perfuses unanticoagulated whole blood through a hollow fiber. A leak in the fiber is created by a precision needle, and the resulting pressure fluctuations within the fiber are monitored to examine the ability of the hemostatic system to close the leak by forming a stable platelet plug.

RESULTS

Both ionic and nonionic CM (25% CM/blood, v/v) were shown to lengthen the mean in vitro bleeding times (IVBTs) compared with normal blood. Ionic CM (ioxaglate and diatrizoate) consistently produced IVBTs longer than 30 min. The nonionic CM iopamidol, iohexol, and ioversol gave mean IVBTs of 16.43, 17.63, and 19.84 min, respectively.

CONCLUSION

Of the three nonionic CM tested, iopamidol had the greatest probability (31%) of producing an IVBT in the normal range, with probabilities of 5% and 7% for iohexol and ioversol, respectively. Thus, iopamidol offered the least anticoagulant effect among the ionic and nonionic CM we studied.

Contrast media effects on hemostatic and thrombotic parameters. Possible consequences for practical techniques and prophylactic measures

This paper reviews the basic mechanisms of the thrombohemorrhagic balance and ways in which contrast media (CM) influence these processes. Coagulation and platelet functions are strongly inhibited by ionic CM, but weakly so by nonionic CM, whereas the former are more detrimental to endothelium, and thus thrombogenic in this sense. Some observations indicate a lower rate of thromboembolic events with the ionic CM in percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG), but this purported difference does not effect mortality or frequency of re-PTCA and emergency CABG. Thus, to challenge these events, strong acting antithrombotics, which also, unlike heparin, inactivate fibrin-bound thrombin, are necessary. Aggressive anti-atherogenic prophylaxis may hamper both thrombosis and reocclusion. The ideal antithrombotic in this setting is yet to be found.

Platelet adhesion/aggregation in an in vitro model of coronary artery stenosis

Platelet adhesion/aggregation (PAA) at a site of coronary artery stenosis is believed to be a process strongly modulated by local shear rates and the functional state of neighboring endothelium. One purpose of the present work, therefore, is to describe an in vitro model for the direct imaging of such PAA. Another is to apply the model to the question as to whether the use of nonionic vs. ionic contrast media (CM) in the presence of vascular endothelium contributes to PAA at the stenosis site. Toward these ends, we utilized a special flow chamber which incorporates a monolayer of endothelial cells (ECs), a step 66% flowpath constriction at a site preadsorbed with microfibrillar collagen, and arterial shear rates. By epifluorescence microscopy and digital image analysis of video recordings, PAA was found to be greater with dysfunctional ECs (pretreated with lysine acetylsalicyclate) than with normal ECs, thereby confirming a modulatory role in PAA of functionally intact ECs. When nonionic (iohexol) or ionic (ioxaglate, diatrizoate) CM was added to the flowing blood at a concentration of 20% by non-red cell volume, PAA was inhibited in the order diatrizoate > ioxaglate > iohexol > saline control. No inhibition by any CM was seen, however, when chamber prefill culture medium containing 20% by volume CM was displaced by CM-free blood, in simulation of bolus administration of CM. In terms of inhibition of PAA during percutaneous transluminal coronary angioplasty (PTCA), therefore, our model provides a conceptual basis by which one may anticipate in flowing blood no clear benefit of ionic over nonionic CM.(ABSTRACT TRUNCATED AT 250 WORDS)