Effects of low osmolar contrast (iomeprol) on haemorheology and platelet activation in patients with coronary artery disease.

BACKGROUND: Non-ionic low osmolar contrast agents are widely used during coronary angiography. As these agents cause activation of thrombotic pathways in vitro, this may have potentially significant clinical impact. However, limited evidence exists as to their in vivo effects from selective coronary cannulation.
METHODS: We initially performed an in vitro experiment to assess the effect of serial contrast (Iomeprol 300, Bracco) dilution on platelet indices [mean platelet count (MPC), platelet volume (MPV), platelet granularity (MPG)]. The in vivo effect of contrast injection on platelet activation markers [soluble P-selectin (sPsel), soluble CD40 ligand (sCD40L)], MPC, MPV, MPG, haemoglobin and haematocrit was subsequently determined in 35 patients (mean age 58 +/- 11; 22 males) undergoing cardiac catheterisaton.
RESULTS: No significant in vitro effect of contrast on MPC or MPV was seen but there was a significant increase in MPG (p = 0.40, 0.10 and 0.01, respectively). In the in vivo study, there was a reduction in mean haemoglobin and haematocrit levels, suggesting an average increase in plasma volume of 6.5 +/- 5.8%. The in vivo effect of Iomeprol was associated with an unadjusted reduction in sPsel concentrations (p = 0.04) and MPV (p < 0.05), with denser platelets (p < 0.05). There was no difference in MPC or sCD40L concentration (both p = NS). After adjustment for the haemodilution effect, no significant reduction in P-sel levels was seen with contrast (p = 0.27), although the adjusted post-contrast change in MPG (p = 0.01), MPC (p = 0.01) and sCD40L (p < 0.05) levels were significant.
CONCLUSION: Low osmolar contrast led to a minimal effect on soluble and physical indices of platelets within the coronary artery, primarily due to plasma volume expansion.