Post-Operative Thrombocytopenia After Bio-prosthesis Implantation
Condition: Thrombocytopenia
MeSH terms: Thrombocytopenia
Study type: Observational

Summary: 
      The objective of the study is to obtain the clinical data from patients who received a
      biological prosthesis in aortic or mitral position, in order to evaluate the occurrence of
      peri-operative thrombocytopenia.

      The aim of the study is to analyze the eventual clinical impact of the phenomenon
      (re-operation for bleeding, blood transfusion) and the mortality rate.

      This is a multicentre retrospective, observentional clinical study. This study will enroll up
      to 5000 patients since 2000 to date.
    

Detailed description: 
      Cardiac surgery is commonly associated with a transient post-operative decrease in the
      platelet count. Thrombocytopenia after cardiopulmonary bypass can be explained by
      hemodilution, exposure to artificial surfaces with platelet activation and adhesion,
      hypothermia, blood loss and mechanical sequestration. It usually occurs between the second
      and third postoperative days, resulting in a reduction of platelet counts by 40-50% from
      baseline values. Moreover, when a foreign body as a valve prosthesis is literally placed into
      the blood flow, blood cells are constantly exposed to its surface and eventually inflammatory
      and, perhaps, autoimmune reactions could start. The interactions biomaterial-blood induce
      changes in platelet shape, metabolism as well as receptor-mediated dysfunction and lysis.
      Then, any significant decline in the circulating platelet count raises concerns about
      coagulation disorders and bleeding.

      Despite the advanced hemodynamic performance, recently thrombocytopenia (defined as nadir
      platelet count < 150.000 x 1000/uL) has been associated to new aortic biological prostheses,
      either rapid deployment or trans-catheter valves. Although several studies have been carried
      on, the drop in the platelet count after aortic valve replacement with certain tissue valves
      remains unexplained yet. The decrease after the valve implantation, however, is not
      exclusively limited to the surgical prostheses. Trans-catheter aortic valves, in fact, were
      found to be associated to post-procedure thrombocytopenia. Thrombocytopenia following
      transcatheter aortic valve implantation (TAVI) procedures is related to the increased adverse
      events rate such as death, stroke, acute kidney injury, bleeding and vascular complications.
      Furthermore, thrombocytopenia seems to occur most likely associated after balloon-expandable
      valves implantation.The literature, however, is confounding.

      Despite several studies, little is known about the mechanism involved. Variations in
      biocompatibility of valve tissue as like a strong immune/inflammatory response could be some
      explanations. However, there is still uncertainty about the mechanism conditioning
      post-operative platelet drop. To address this uncertain the underlying process should be
      evaluated in a large multicentre trial.

      The aims of the study are the following:

        -  to analyze the occurrence of thrombocytopenia after isolated aortic valve
           replacement/implantation and after isolated mitral valve replacement;

        -  to evaluate the clinical impact of thrombocytopenia (length of stay, bleeding,
           re-operation for bleeding, blood transfusion, mortality).

      The study is multicentre, retrospective, observational and will enroll up to 5000 since 2000
      to date.
    

Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        The population is composed by adult patients submitted to isolated aortic valve
        replacement, percutaneous trans-catheter aortic valve implantation, and mitral valve
        replacement with a bio-prosthesis.