Shortened megakaryocyte-platelet regeneration time in young survivors of myocardial infarction.

Abstract

Megakaryocyte-platelet regeneration time (MPRT) was determined 6 to 12 months after myocardial infarction in 42 patients below the age of 45 years (mean age +/- SD = 39.4 +/- 4.6, range 23 to 44) and in 11 healthy control subjects by measurement of the reappearance rate of platelet cyclooxygenase activity after oral aspirin. In the young post infarction patients, MPRT was correlated to pertinent metabolic, angiographic, and clinical findings. MPRT for all patients tended to be shorter than in control subjects (t1/2 = 4.53 +/- 1.15 vs 5.22 +/- 0.52; p less than 0.10). Age, present tobacco consumption, serum lipoprotein lipid concentrations, and glucose tolerance, as well as other measured risk factors, did not correlate significantly with MPRT. A marked difference in MPRT, independent of risk factor profile, was present between patients with and without hemodynamically significant stenoses in the coronary angiogram (4.06 +/- 0.92 vs 5.22 +/- 1.07; p less than 0.001). It is suggested that a shortened platelet survival in young post infarction patients is secondary to platelet activation by high-velocity flow and shear forces at the sites of proximal coronary artery stenoses.