Contrast Agents and High-Risk PCI
abstract & commentary
Synopsis: In patients with acute coronary syndromes, the nonionic iso-osmolar agent iodixanol is associated with a 45% reduction in in-hospital major adverse events when compared to the low-osmolar ionic agent ioxaglate.
Source: Davidson CJ, et al. Circulation 2000;101: 2172-2177.
Studies have shown that the newer low-osmolarity nonionic contrast agents decrease major complications of angiography as compared to the traditional high-osmolar ionic agents, but have less anticoagulation activity. The latter property could be a problem in high-risk patients with unstable coronary syndromes where thrombus formation is frequent before and after percutaneous interventions (PCI). Thus, there has been interest in low-osmolar (low side effects) ionic agents such as ioxaglate. The study of contrast media use in high-risk percutaneous coronary angioplasty (COURT) was conducted in multiple centers to compare ioxaglate to iodixanol, a nonionic iso-osmolar agent, in 856 high-risk patients undergoing PCI. All patients received usual care including aspirin, ticlopidine, abciximab, and heparin at the operator’s discretion, but were prospectively randomized to the two contrast agents in a double-blind protocol. High-risk patients were defined as those with class IV angina within 48 hours, evolving acute myocardial infarction (MI), or ischemia within two weeks of acute MI. One thousand four hundred eighty-five met these criteria and 856 underwent PCI, but 851 were able to be evaluated. Among these 815 patients, 60% had POBA and 30% had stents placed. Abciximab was used in about 40%. The activated clotting times (ACTs) and the volume of contrast agent were similar between the two groups. The primary end points were seven major in-hospital clinical events: emergency recatheterization or PCI for ischemia; abrupt closure of the target vessel; stroke; systemic embolism; periprocedure MI; coronary artery bypass graft (CABG); and cardiac death. Secondary end points included eight major procedural complications: target vessel thrombus, distal embolism, side vessel occlusion, and no reflow; plus balloon pump need, antiplatelet therapy use, or an unsuccessful procedure. There was a low incidence of in-hospital events overall, but fewer occurred with iodixanol as compared to ioxaglate (5.4 vs 9.5%; P = 0.027) mainly due to target vessel abrupt closure (0.7% vs 2.4%) and MI (2% vs 4.4%, both P = 0.05). From discharge to 30 days there were no differences in events. Procedural success was also higher with iodixanol (92% vs 86%; P = 0.004). Davidson and colleagues conclude that in patients with acute coronary syndromes the nonionic iso-osmolar agent iodixanol is associated with a 45% reduction in in-hospital major adverse cardiac events when compared to low osmolar ionic agent ioxaglate.
Comment by Michael H. Crawford, MD
This controlled trial demonstrates that a lower osmolarity nonionic contrast agent is not inherently thrombogenic in vivo and is associated with fewer major adverse cardiac events and better procedural success. Thus, among the lower osmolarity agents that cause less patient discomfort and side effects, the nonionic agent seems superior and the in vitro concern about thrombogenicity did not materialize in vivo. This study is an advance over other studies of contrast agents because it exclusively dealt with high-risk patients and used contemporary techniques such as abciximab and stents. Consequently, the data are compelling despite the higher costs of these newer agents.
There are some limitations to this study. Since it only involved acute coronary syndrome patients, the results are not necessarily transferable to stable patients. Also, some may argue that the use of abciximab and stents was below the current frequency of use, but at least these therapies were used. Thus, in these high-risk patients, the added cost of this newer agent in the present era seems justifiable given the impressive results of this randomized, double-blind trial.
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