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Systemic platelet effects of contrast media: implications for cardiologic research and clinical practice
M C D Dalby1, S J Davidson, J F Burman
1Department of Cardiology, Royal Brompton and Harefield National Health Service Trust, London, United Kingdom.
Insights
Ionic contrast media, unlike nonionic types, demonstrate a systemic antiplatelet effect during diagnostic angiography, impacting platelet aggregability. This finding may explain clinical outcomes and confound platelet studies.
Area of Science:
- Cardiovascular Medicine
- Hematology
- Pharmacology
Background:
- Angiographic contrast media are known to activate platelets and reduce aggregability in vitro.
- Previous research indicated a local antiplatelet effect of contrast media during angioplasty.
- The systemic impact of contrast media on platelet function remained uninvestigated.
Purpose of the Study:
- To determine if diagnostic angiographic doses of contrast media exert a systemic antiplatelet effect.
- To compare the systemic effects of nonionic (iohexol) and ionic (ioxaglate, diatrizoate) contrast media on platelet function.
Main Methods:
- Thirty patients undergoing coronary angiography were randomized to receive iohexol, ioxaglate, or diatrizoate.
- Platelet aggregability was assessed before and after angiography using whole blood electrical impedance aggregometry (WBEA) and the PFA-100 analyzer.
Main Results:
- Whole blood electrical impedance aggregometry revealed a significant decrease in platelet aggregability after administration of ionic media (ioxaglate and diatrizoate), but not with nonionic iohexol.
- The PFA-100 analyzer showed no significant changes in closure time for any contrast medium tested.
- Ionic contrast media, particularly diatrizoate, induced a more pronounced antiplatelet effect compared to ioxaglate when measured by WBEA.
Conclusions:
- Ionic contrast media, but not nonionic media, exhibit a systemic antiplatelet effect at diagnostic angiographic doses as measured by WBEA.
- This systemic effect of ionic contrast media has not been previously demonstrated.
- The findings may elucidate improved clinical outcomes associated with ionic media and highlight potential confounding factors in platelet studies during coronary angioplasty.
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.
Method:
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.