CONCLUSIONS

Damping of the pressure waveform on selective engagement may indicate significant ostial stenosis.

SPECIAL ISSUES/CONSIDERATIONS Contrast Selection and Renal Insufficiency An optimal diagnostic angiographic should allow for complete examination of the arterial bed with the least amount of contrast used. In patients with renal insufficiency, it is critical to minimize the amount of contrast used during the angiographic study. Low osmolar contrast agents are preferred as they minimize patient discomfort and both reduce the risk of contrastinduced nephropathy (CIN) and allergic reactions. The only available iso-osmolal contrast agent, iodixinol, may be associated with a lower risk of nephropathy than low osmolal agents, particularly among patients at high risk for contrast nephropathy (35). Despite the lower risk of complications with these agents, the possibility of CIN and allergic reaction remain. Carbon dioxide (CO2) angiographic imaging is an alternative in patients who remain at high risk for these complications. CO2 is a very dissolvable gas that is nontoxic to the kidneys and is nonallergic (36,37). It works by displacing blood cells inside the vessel, effectively reducing the radiographic density within the lumen. There are certain limitations to this form of imaging that should be noted. Importantly, contrast resolution with CO2 angiography, while often adequate, is inferior to that with traditional iodinated contrast agents (38). CO2 angiography must also be performed in a controlled fashion with carefully administered gas volumes to avoid gas trapping in the pulmonary circulation (39). Gadolinium also has been studied as a possible alternative agent in patients at risk for CIN. However, this agent has not been proven to have any significant advantage over low osmolar agents in reducing CIN and has been largely abandoned (40).