Platelet aggregometry cannot identify uremic platelet dysfunction in heart failure patients prior to cardiac surgery.

BACKGROUND: Patients with heart failure often have concomitant renal disease which can result in uremic platelet dysfunction. Determining whether uremia has affected platelets by platelet aggregometry can be challenging in these patients since they are often on antiplatelet medications. This study was undertaken to determine if platelet aggregation studies could identify heart failure patients at risk for uremic bleeding prior to cardiac surgery. METHODS: Platelet aggregation studies from three groups were studied and compared: 17 heart failure patients with mild to moderate renal impairment, 17 heart failure patients without renal abnormalities and 17 healthy volunteers. RESULTS: Platelet aggregation was severely impaired in both heart failure groups with and without renal abnormalities compared to healthy controls, and there were no significant differences in platelet aggregation in response to any of the agonists. There was a pan-decrease in platelet aggregation to all agonists in all heart failure patients. CONCLUSION: Platelet aggregometry does not appear to be useful in measuring platelet dysfunction in heart failure patients with mild to moderate renal impairment.

Clot Strength as Measured by Thrombelastography Correlates with Platelet Reactivity in Stroke Patients.

OBJECTIVE: Platelet reactivity may be important in the management of patients with stroke. However, degree of platelet reactivity has not been correlated with Thrombelastography (TEG(®)) parameters in stroke. We sought to detect a correlation between TEG(®) values and clot platelet reactivity in ex vivo clots of stroke patients. METHODS: We collected venous blood from 40 patients with stroke. TEG(®) measurements were carried out and residual clots were fixed in 10% formalin immediately following completion of TEG(®). The formalin specimens were embedded in paraffin blocks, cut at 4 micrometers, and stained with CD 61 (immunohistochemical stain used to detect platelets) with appropriate controls. Under light microscopy, three pathologists blinded to TEG(®) results independently graded CD61 intensity (how aggregated/intense the CD61 stained) into a low and high group, as a proposed measurement representing the platelet reactivity of the clot. We compared pre-tPA-TEG(®) values among groups with different CD 61 intensities. RESULTS: After adjusting for confounding factors, we found statistically significant correlation between CD61 staining and several TEG(®) parameters (Delta and CD61 staining intensity (p=0.047); Angle and CD61 staining intensity grade (p=0.04); and G and CD61 staining intensity grade (p=0.04)). CONCLUSIONS: Clot strength on TEG(®) as measured by Delta, Angle, and G correlates with a clot with greater platelet reactivity.