Background

Von Willebrand Factor (vWF) plays an important role in hemostasis and vascular inflammation.  In blood stream vWF is present in a non-covalent complex with factor VIII, one of the largest coagulation factors. Acquired von Willebrand syndrome (AvWS) is a rare disorder but it is often related to cardiovascular diseases, especially congenital and valvular heart diseases as previously described in patients with Heyde syndrome. The present study investigates possible implications of acquired von Willebrand Syndrome and factor VIII in patients with moderate to severe mitral regurgitation undergoing the MitraclipÓ procedure.

Methods and Results

From August 2017 to September 2018 62 patients with moderate to severe mitral regurgitation were prospectively enrolled in our single-center RETORT-MR trial (Regensburg Trial on TMVR Techniques in Mitral Regurgitation). All included patients were treated using the MitraclipÓ procedure. In 27.4% of patients primary mitral regurgitation was present (n=17), in two cases a combined entity of mitral regurgitation had been diagnosed (3.2%) and 69.4% (n=43) suffered from a secondary mitral regurgitation. Measurements of von Willebrand Factor activity (vWFAct), von Willebrand antigen (vWFAg) and factor VIII before and four weeks after the MitraclipÓ procedure were available in 41 patients. At baseline 8 patients had a history of gastointestinal bleeding, whereas bleedings occured in two patients four weeks after the MitraclipÓ procedure. Patients with blood type 0 (n=11) had significantly lower values concerning vWFAct at baseline (150.5 ± 54 %) than patients with blood type A, AB or B (n=29), (229.7 ± 100 %, p=0.003) as well as at four week follow-up (blood type 0 174.0 ± 70 % vs. 226.2 ± 72.9 %, p=0.042). In contrast no significant changes of vWFAct and vWFAg occured within the groups of blood type 0 and blood types A, AB or B at baseline and four week follow-up. 

Irrespective of blood types mean vWFAct was 206.7 ± 95 % at baseline and 208.3 ± 76 % at four week follow-up (p=0.899).  The measured vWFAg was 259.3 ± 133 % at admission and 249.5 ± 111 % at four week follow-up (p=0.444). In contrast to vWFAct and vWFAg significant changes were revealed in the measurements of factor VIII (212.0 ± 74 % at baseline and 191.7± 74 % at four week follow-up, p=0.0323).

Conclusion

Interestingly the values of factor VIII significantly decreased in patients who underwent successfull MitraclipÓ procedures despite the hypothesis of reducing shear stress of mitral regurgitation. In contrast morphological changes of the mitral valve through MitraclipÓ implantation may also induce shear stress. However no significant changes in vWFAct and vWFAg values were revealed after MitraclipÓ implantation and the number of patients with bleeding events was very small.