Freedom SOLO-Associated Thrombocytopaenia is Valve-Dependent and Not Due to In Vitro Pseudothrombocytopaenia.
BACKGROUND
Use of the Freedom SOLO (FS) stentless aortic bioprosthesis is limited by a unique and as yet unexplained severe decrease in postoperative platelet count in the absence of FS-related excess bleeding or thromboembolism. We investigated whether anticoagulant-associated pseudothrombocytopaenia could explain this complication.


METHODS
Thirty consecutive patients (mean age 75.4±7.7 years, 11 [36.7%] female) underwent elective aortic valve replacement (AVR) with either the stented bovine Mitroflow (MF, n=18) or the stentless bovine FS (n=12) aortic valve bioprostheses. Serial platelet counts were performed simultaneously with sampling tubes containing tripotassium (K3-)-EDTA, trisodium (Na3)-citrate, or novel alternative magnesium sulfate (MgSO4, ThromboExact™)-based anticoagulant, respectively.


RESULTS
Postoperative platelet counts decreased compared with preoperative values in all patients (p<0.001), but were significantly lower in patients receiving FS compared to MF at all measurement time points until the end of observation (day 9). Lowest platelet counts were seen on the first postoperative day for MF (mean reduction: -41.5%) and on the second postoperative day for FS (mean reduction: -59.9%). Postoperative platelet counts did not correlate with any of the anticoagulants, thereby indicating no pseudothrombocytopaenia in the study population. There was no interaction between anticoagulant and type of valve. Only 1% of variance in platelet counts was caused by the anticoagulant, 46% by the day of measurement relative to baseline, and 20% was caused by the type of valve.


CONCLUSIONS
The platelet-lowering effect in patients receiving the FS is valve-dependent and is not caused by systemic preanalytical (laboratory) measurement error such as anticoagulant-dependent pseudothrombocytaemia, particularly with EDTA and citrate.
Surgical Department, Saint John of God Hospital, Kajetanerplatz 1, 5010 Salzburg, Austria. Electronic address: oh.stanger@gmail.com.
Olaf
O
Stanger
Inselspital University Hospital and University of Berne, Berne, Switzerland.
Brigitta
B
Gahl
Inselspital University Hospital and University of Berne, Berne, Switzerland.
Michael
M
Grabherr
University Department of Cardiac Surgery, Salzburg Paracelsus Medical University, Salzburg, Austria.
Richard
R
Krausler
Inselspital University Hospital and University of Berne, Berne, Switzerland.
Sarah
S
Longnus
Department of Laboratory Medicine, Graz Auenbrugger University Hospital, Austria.
Andreas
A
Meinitzer
Department of Laboratory Medicine, Paracelsus Medical University, Salzburg, Austria.
Janne
J
Cadamuro
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001021:Aortic Valve / Q000601:surgery*; D001705:Bioprosthesis / Q000009:adverse effects*; D002417:Cattle; D005260:Female; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D019918:Heart Valve Prosthesis Implantation / Q000009:adverse effects*; D006801:Humans; D008297:Male; D010976:Platelet Count; D011183:Postoperative Complications / Q000097:blood*; D013921:Thrombocytopenia / Q000097:blood / Q000209:etiology
Anticoagulant; Aortic valve replacement; Biomaterials; Cardiac surgery; Platelets; Stentless