SAN DIEGO – Contrast agents administered through the coronary vessels for invasive angiography led to significantly more kidney damage than contrast agents administered intravenously for coronary computed tomography angiography, according to a randomized study.
In the Coronary Artery Disease-Management (CAD-Man) study, contrast-induced kidney injury was two to three times more likely after intracoronary than after intravenous contrast administration, explained study investigators Dr. Eva Schönenberger and Dr. Marc Dewey of Charité Medical University, Berlin.
Contrast agents used to detect and treat blockages in coronary arteries are known to damage the kidneys in 2%-20% of patients. In the United States, about 4 million doses of contrast are administered directly into the coronary vessels during invasive catheterization, and 40 million into superficial veins, said Dr. Dewey, Heisenberg Professor of Radiology at the German Research Foundation and vice chair of the department of radiology at Charité.
That makes contrast administration a significant clinical decision for physicians, he added, not just because of potential for harm, but also the potential for added costs.
CAD-Man included 326 patients with suspected coronary disease. Researchers randomized 161 patients to intracoronary contrast agent (ICA) for invasive coronary angiography and 165 patients to IV contrast agent for coronary computed tomography angiography (CTA). All patients received the same contrast agent.
Blood samples were taken at baseline before the procedure, and at two time points after: between 18 and 24 hours, and between 46 and 50 hours. Baseline creatinine levels were similar in the two groups. The researchers defined contrast-associated nephrotoxicity as an increase in creatinine of at least 0.5 mg/dL, or 25%.
At follow-up, 21 of 158 ICA patients (13%) and 9 of 160 CTA patients (6%) had contrast-associated nephropathy, a significant difference (P less than .05). In patients without coronary disease, 13% of ICA patients and 4% of CTA patients developed contrast-associated nephropathy, also a significant difference (P less than .05).
Catheter administration concentrates more contrast in the heart and above the kidneys than intravenous administration, Dr. Schönenberger explained at the meeting sponsored by the American Society of Nephrology. Thus, the increased kidney damage in invasive-angiography patients may be due to higher dosages of contrast in their kidneys.
Physicians “have to keep in mind that putting contrast agents directly into the coronaries might produce more of an increase of creatinine, and more acute kidney injury, than just giving it through an IV,” explained Dr. Schönenberger, a nephrologist in the department of anesthesiology and operative intensive care medicine at Charité.
Physicians should take this information into consideration when deciding how to administer contrast for patients suspected of having coronary artery disease, Dr. Dewey noted. “In addition to being noninvasive, cardiac CT may thus also have the advantage of reducing kidney risk.”
Cost should be a big concern as well. Dr. Dewey referred to published literature indicating that contrast-induced kidney injury can lead to “longer hospital and intensive care unit stays, [increased] dialysis, cost of adverse events, and higher mortality rates. The in-hospital cost was $10,000 per contrast-induced acute kidney injury, and the 1-year cost of treatment was more than $11,000.”
Because CAD-Man’s last patient was enrolled in mid-September, the data are still being analyzed, Dr. Schönenberger noted. Therefore, some confounders may be discovered that influenced the results.
For example, cardiologists may select their sicker patients for invasive procedures in order to be ready to insert stents, so there may not be as much flexibility in which approach to use.
Also unclear is the amount of contrast used for each patient in each arm of this study. Some physicians may have used more contrast for patients suspected of having disease that was harder to detect, although that part of the analysis remains under review, Dr. Dewey and Dr. Schönenberger said.
It remains unclear whether the nephrotoxicity found in the invasive angiography group was all due to the contrast, Dr. Schönenberger noted, or whether some of it might have been caused by small particles of hardened cholesterol spreading to blood vessels in the kidneys – a process known as atheroembolic renal disease. That, too, is under review.
The contrast agent used in the study, low-osmolar nonionic Xenetix 350, is used in 96 countries but is not approved by the U.S. Food and Drug Administration, Dr. Schönenberger said. However, it is very similar to those agents that are in use in the United States, she added.
The study was funded by the German Research Foundation through the Heisenberg Professorship Program. The researchers reported no financial disclosures.