Platelet kinetics in congenital heart disease.
The survival of 111indium labelled platelets has been determined in a series of 47 subjects comprising nine with cyanotic congenital disease (Eisenmenger's syndrome), seven with congenital heart disease associated with left to right shunts, six with primary pulmonary hypertension, six with peripheral vascular disease, 11 with cardiac disorder associated with low cardiac output and eight normal volunteers. Compared with the value in the normals of 9.5 days, mean survival was significantly shortened in those with Eisenmenger's syndrome (8.4 days) and with peripheral vascular disease (8.5 days). It was normal in patients with left to right shunts (9.5 days). Gamma camera imaging in selected patients failed to reveal any abnormal sites of deposition of labelled platelets except in one patient with peripheral vascular disease who had bilateral abnormal activity in his lower limbs and a shortened platelet survival (8.0 days). From theoretical considerations, it was concluded that the reduction in platelet survival in Eisenmenger's syndrome was such that, had it been the result of pulmonary intravascular platelet deposition, abnormal activity should have been visible on chest scanning with the gamma camera. The absence of scintigraphic evidence of abnormal platelet deposition in the lungs of these patients, combined with the linear configuration of their platelet survival curves, suggests that the accelerated platelet destruction is in the reticuloendothelial (RE) system rather than intravascular. Indirect evidence in favour of increased RE destruction of platelets in Eisenmenger's syndrome was the finding of an approximate doubling of intrasplenic platelet transit time, indicating abnormal platelet pooling within the spleen.