title: Systemic platelet effects of contrast media: implications for cardiologic research and clinical practice.
abstract: BACKGROUND
  Angiographic contrast media cause platelet activation and decrease aggregability in vitro. We have previously shown in vitro a significant antiplatelet effect of contrast media at the concentrations obtained locally in the coronary artery during angioplasty. It is not known, however, whether a systemic effect is present.
  
  
  METHODS
  Thirty patients undergoing diagnostic coronary angiography were prospectively randomized to receive the nonionic medium iohexol, ionic low-molecular-weight medium ioxaglate, or ionic high-molecular-weight medium diatrizoate. Platelet aggregability was measured before and after the investigation with whole blood electrical impedance aggregometry (WBEA) with collagen agonist and the PFA-100 (Dade, Miami, Fla) platelet function analyzer with combined shear, collagen, and adenosine diphosphate as agonists.
  
  
  RESULTS
  With WBEA, with iohexol no difference in impedance change was seen: (medians and ranges) before, 9.8 Omega (4.8-19.2 Omega) versus after, 9.6 Omega (2-19.2 Omega) (P not significant [NS]). With ioxaglate a significant fall was seen: before, 8.6 Omega (6.4-15.2 Omega) versus after, 6.6 Omega (0-12.4 Omega) (P =.004). With diatrizoate a significant and greater fall was seen: before, 10.8 Omega (6.4-17.6 Omega) versus after, 6.6 Omega (0-10.8 Omega) (P =.002). With PFA, no difference in closure time was seen with any medium: iohexol before, 99 seconds (79-142 seconds) versus after, 142 seconds (63-128 seconds) (P NS); ioxaglate before, 120 seconds (75-258 seconds) versus after, 95 seconds (74-258 seconds) (P NS); and diatrizoate before, 114.5 seconds (65-250 seconds) versus after, 100.5 seconds (72-300 seconds) (P NS).
  
  
  CONCLUSIONS
  Ionic but not nonionic contrast media have a systemic antiplatelet effect at diagnostic angiographic doses when measured with WBEA. Such an effect has not been shown before. This may explain the observed improved clinical outcome with ionic contrast media but also might confound platelet studies in coronary angioplasty.
authors.affiliation: Department of Cardiology, Royal Brompton and Harefield National Health Service Trust, London, United Kingdom.
authors.forename: M C D
authors.initials: MC
authors.lastname: Dalby
authors.forename: S J
authors.initials: SJ
authors.lastname: Davidson
authors.forename: J F
authors.initials: JF
authors.lastname: Burman
authors.forename: J
authors.initials: J
authors.lastname: Clague
authors.forename: U
authors.initials: U
authors.lastname: Sigwart
authors.forename: S W
authors.initials: SW
authors.lastname: Davies
mesh_terms: D000328:Adult; D000368:Aged; D003287:Contrast Media / Q000494:pharmacology*; D017023:Coronary Angiography; D003973:Diatrizoate / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007472:Iohexol / Q000494:pharmacology*; D007485:Ioxaglic Acid / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D015539:Platelet Activation / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects*; D011446:Prospective Studies
chemical_list: D003287:Contrast Media; D003973:Diatrizoate; D007472:Iohexol; D007485:Ioxaglic Acid