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 T 1/2 was determined in 16 patients with substituted valves (10 PH and 6 MP). Average platelet T 1/2 in PH (2.9 +/- 0.6 d) was similar (p greater than 0.05) to MP (3.2 +/- 0.6 d), and both were considerably lower (p less than 0.05) than platelet T 1/2 in normal subjects (NL, 5.1 +/- 0.5 d). Furthermore, platelet T 1/2 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.