Multiple electrode whole-blood aggregometry and bleeding in cardiac surgery patients receiving thienopyridines.

Background: Preoperative treatment with thienopyridines is associated with increased postoperative bleeding in cardiac surgery patients. Patients under treatment with thienopyridines have different levels of platelet dysfunction and the effects of discontinuation are not totally predictable. The present study aimed to determine if a preoperative assessment of platelet function in these patients could provide clinically relevant information regarding the risks of excessive postoperative bleeding and transfusion requirements.

Methods: This is a retrospective analysis of prospectively collected data. Patients (n=87) under thienopyridine treatment until at least one week before cardiac surgery were enrolled in the study. Platelet function was assessed preoperatively with multiple electrode aggregometry: the adenosine diphosphate (ADP) test and TRAP (thrombin receptor-associated peptide) test were performed for all patients.

Results: Univariate analysis revealed that postoperative bleeding was associated (p<0.1) with preoperative serum creatinine level, platelet count, CPB (cardiopulmonary bypass) duration, and results from the ADP test and the TRAP test. Multivariable linear regression analysis confirmed the CPB duration (p=0.049) and ADP test (p=0.007) as independently associated with postoperative bleeding. The relationship between the ADP test and postoperative bleeding was investigated with polynomial regression analysis, and a logarithmic equation provided the best fit. The accuracy of prediction was good (area under the curve 0.71, p=0.013), with a cutoff value for the ADP test at 31 U (sensitivity 72%, specificity 66%, negative predictive value 92%, and positive predictive value 29%).

Conclusions: The multiple electrode aggregometry ADP test in patients under thienopyridine treatment and undergoing cardiac surgery is associated with postoperative bleeding and platelet transfusion and provides an accurate preoperative prediction of postoperative bleeding risk.