Thrombocytopenia after aortic valve replacement: comparison between mechanical and biological valves.

BACKGROUND AND AIM OF THE STUDY Concerns have been recently raised regarding the postoperative decrease in platelet count after aortic valve replacement (AVR). Thus, a retrospective analysis was conducted of patients after AVR with regards to postoperative platelet count. METHODS The data were analyzed from all patients undergoing AVR with (n = 829) or without (n = 1,230) coronary artery bypass grafting (CABG) at a single center between January 1998 and May 2009. The lowest (minimum) platelet count within the first five postoperative days was determined. RESULTS The patients received either an ATS mechanical prosthesis (ATS; n = 401), a St. Jude Medical mechanical prosthesis (SJM; n = 791), a Carpentier-Edwards Perimount bioprosthesis (CEP; n = 618), a Medtronic Freestyle stentless bioprosthesis (FRE; n = 213), or a Sorin Freedom Solo stentless bioprosthesis (SFS; n = 36). By using a multivariate linear regression model, the following independent risk factors for a lower postoperative platelet count were revealed: age, body surface area, active endocarditis, preoperative platelet count, duration of extracorporeal circulation, number of grafts, valve size, and units of transfused fresh-frozen plasma and red blood cells. On entering the type of prosthesis into the multivariate linear regression analysis, together with the other risk factors, patients with CEP and FRE valve prostheses had a lower minimum postoperative platelet count than those with mechanical prostheses (ATS and SJM). CONCLUSION Patients undergoing AVR with the Carpentier-Edwards Perimount bioprosthesis or a Medtronic Freestyle stentless bioprosthesis had a lower minimum platelet count within the first five postoperative days, compared to patients receiving ATS and St. Jude Medical mechanical prostheses. No differences were identified between the Sorin Freedom Solo and all other valve prostheses.