Br. Travis et al., The sensitivity of indicators of thrombosis initiation to a bileaflet prosthesis leakage stimulus, J HEART V D, 10(2), 2001, pp. 228-238
Background and aim of the study: The recent clinical history and experiment
al studies of the Medtronic Parallel (MP) valve suggest that bileaflet valv
e leakage flow is a primary initiator of thrombosis. These studies investig
ated the effects of physiologic leakage flow through a MP valve on various
markers of blood damage.
Methods: A centrifugal pump was used to drive whole, human blood anticoagul
ated with PPACK through a circuit containing a MP 27 mm valve in the closed
position (experimental runs) or a MP 27 mm valve in the open position (con
trol runs). Samples were taken at set time intervals after the start of the
pump. These samples were analyzed by cell counting, flow cytometry, and EL
ISA.
Results: Cell counts remained relatively constant in both the experimental
and control runs. Increases in plasma hemoglobin concentration and the perc
entage of glycophorin A-positive fragments in the cell population were not
significant in either the experimental or the control runs. Plasma platelet
factor 4 activity and the percentage of the CD41-positive population which
was positive for annexin V increased significantly (p <0.05) in the experi
mental runs compared with the control runs.
Conclusion: The results indicate that bileaflet valve leakage flow causes s
ignificant platelet disruption, that erythrocytes are more resistant to dis
ruption by leakage flow than platelets and granulocytes, and that annexin V
binding to platelets and plasma platelet factor 4 activity are more sensit
ive markers of leakage induced blood damage than plasma hemoglobin concentr
ation.