Impairment of platelet retention rate in patients with severe aortic valve stenosis

Abstract

Background: Recent reports revealed the presence of acquired von Willebrand syndrome type 2A in patients with aortic valve stenosis (AS). von Willebrand factor (vWF) has been shown to play a vital role in platelet adhesion. Therefore, we measured the platelet retention rates, which reflect platelet adhesion, in patients with severe AS.

Methods: In addition to echocardiography, routine blood screening tests were performed and the platelet retention rates were measured using collagen-coated bead columns in 21 patients with severe AS and in 21 control subjects.

Results: Patients with severe AS showed the maximum aortic valve pressure gradients of 110.9±22.7 mmHg, and effective orifice areas of 0.59±0.20 cm2. The results of routine blood tests in patients with severe AS were comparable to those of control subjects; however, the platelet retention rates in the AS patients (7.3±5.0%) were significantly lower than those in control subjects (30.5±11.8%, p<0.001). A significant negative correlation was observed between maximum aortic valve pressure gradients and platelet retention rates (r = -0.81, p<0.001). In 8 patients with severe AS, the platelet retention rates increased from 5.8±3.6% to 16.0±2.4% after aortic valve replacement (p<0.001).

Conclusion: These findings suggest that impairment of platelet retention rate is seen in almost all patients with severe AS. Clinicians should be aware of the possibilities of vWF-mediated platelet dysfunction and bleeding tendency in patients with severe AS.

Keywords: Aortic valve stenosis; Platelet retention rate; von Willebrand factor.