Evaluation of Platelet Kinetics following Porcine and Mechanical Valve Replacement

Because thromboembolic pathogenesis in mechanical prosthetic valves (MP) might involve selective MP platelet consumption with consequent reduced platelet survival, it has been suggested that lowered platelet half-life (T_1/2) detection provides identification of postoperative thrombotic risk. Porcine heterografts (PH) possess less thromboembolic hazards than MP; thus, comparative evaluation of PH versus MP platelet T_1/2 is germane to the test's thrombotic predictive value, yet platelet kinetics in PH require elucidation. Accordingly, ₅₁chromium platelet T1/2 was determined in 16 patients with substituted valves (10 PH and 6 MP). Average platelet T1/2 in PH (2.9±0.6 d) was similar (p>0.05) to MP (3.2±0.6 d), and both were considerably lower (p<0.05) than platelet T1/2 in normal subjects (NL, 5.1±0.5 d). Furthermore, platelet T1/2 was below the lowest NL platelet T_1/2 (4.0 d) in seven PH and three MP patients. Thus, frequency and extent of decreased platelet survival in PH are common and equal to MP. These results indicate that platelet half-life does not afford thromboembolic predictability in patients with mechanical valves and, instead, favors prosthetic-induced physical trauma causing abnormal platelet survival.