Nicholas Mark Gutierrez MD, Presenter: Nothing to Disclose

Jeffrey Hooker Newhouse MD, Abstract Co-Author: Research Consultant, PAREXEL International Corporation

Contrast-associated nephropathy occurs more frequently after cardiac angiography, which usually includes left ventriculography via direct left ventricular injection, than after contrast-enhanced CT, despite the usually-higher intravenous contrast dose used for CT. To determine whether maximum renal arterial contrast concentration is higher after left ventriculography, we assessed this parameter for both procedures.

Contrast concentration (% by volume) in abdominal aortic blood during contrast-enhanced CT was measured by performing CT densitometry of aortic blood before contrast, and in the arterial phase, in fifty adults undergoing abdominal CT (100ml iohexol 300mgI/ml 3ml/sec).  Densities  were converted to contrast concentrations by scanning water phantoms containing twenty graded concentrations of contrast and comparing their densities to patient data. Since it was impossible to perform CT densitometry during cardiac angiography, aortic contrast concentrations (% by volume) were calculated from standard contrast doses and injection rates with the range of clinically-encountered cardiac output rates assuming ultimate steady state for blood/contrast mixing and normal data distribution. 

Maximum aortic (and hence renal arterial) concentrations were significantly higher (range: 12.3 - 14.2%) after ventriculography than after CT (3.2 +/-0.9%).  Since ventricular injection times are much shorter than than published initial-appearance-to-maximum-concentration times after intravenous administration, the rate of change of contrast concentration is also higher after ventriculography than after CT.

Higher maximum renal arterial contrast concentration may be responsible for the greater risk of nephropathy after cardiac angiography than after doses for CT. The faster rate of change of renal arterial contrast concentration after ventriculography may also increase the likelihood of renal toxicity.

Maximum renal arterial contrast concentration, and/or the rapidity of change of this parameter, may be partly responsible for the risk of nephropathy.  Controlling these factors might permit reduction of nephropathy risk; they also suggest avenues of research into the pathophysiology of contrast nephropathy.

Gutierrez, N, Newhouse, J, Maximum Renal Arterial Contrast Concentrations in Cardiac Angiography and Contrast-enhanced CT: Implications for Different Contrast Nephropathy Rates.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006109.html