Reduction in platelet count after aortic valve replacement: comparison of three bioprostheses

Concerns have recently been raised regarding postoperative decreases in platelet count (PC) after aortic valve replacement (AVR) with the Sorin Freedom Solo (SFS) stentless bioprosthesis. In order to assess the relevance and the clinical impact of this phenomenon, variations in PC were monitored in patients with SFS valves, and compared to changes of PC in patients after AVR with two other bioprostheses, the Medtronic Mosaic (MOS) porcine valve and the Sorin Mitroflow (MIT) pericardial valve.

Three groups of patients (25 in each group) who had undergone AVR with a biological prosthesis were compared. The patients were similar in terms of their preoperative characteristics, including mean age, NYHA functional class, risk factors, EuroSCORE, and mean PC. The PC was monitored on postoperative days 1, 3, and 5, and again at discharge. Thrombocytopenia was considered to be 'present' when the PC was < 150,000/microl, and 'severe' when the PC was < 30,000/microl.

No significant inter-group differences were observed in the duration of extracorporeal circulation or cross-clamp times. The mean postoperative PCs for MOS valves were 154,000 +/- 56,000/microl, 154,000 +/- 54,000/microl, 161,000 +/- 85,000/microl, and 228,000 +/- 95,000/microl at days 1,3, and 5, and at discharge, respectively. For MIT valves, these values were 126,000 +/- 37,000/microl, 113,000 +/- 38,000/microl, 130,000 +/- 46,000/microl, and 170,000 +/- 50,000/microl, respectively. For SFS valves, the values were 99,000 +/- 27,000/microl, 67,000 +/- 9000/microl, 78,000 +/- 54,000/microl, and 96,000 +/- 32,000/microl, respectively. Severe thrombocytopenia was never observed in any patient. A significant decrease in PC occurred with SFS when compared to MOS valves (on days 1, 3, 5, and at discharge, p < 0.001) and to MIT valves (on days 3, 5, and at discharge, p < 0.005). Multivariate analysis showed older age (p = 0.001) and the SFS valve (p = 0.0002) to be incremental risk factors for developing severe or moderate thrombocytopenia after AVR.

A reduction in PC occurred with all bioprostheses on postoperative day 1, while a significant reduction in PC was continued for SFS valves on postoperative days 3 and 5, when compared to MOS and MIT valves. A normalization of PC at discharge was observed only with MOS valves. Thrombocytopenia after AVR with biological prostheses was not associated with any major postoperative complication.