Summary
Platelet aggregation as induced by A.D.P. has been studied using the fragiligraph.
With this instrument continuous registration for 60 min of the aggregation - disag
gregation - behaviour of platelet rich plasma (P.R.P.) has become practicable and
a number of parameters of the curves could then be defined and analysed. Specimens
from 24 male patients with acute myocardial infarction and 14 normal controls were
compared. P.R.P. of the controls exhibited a short phase of an initial rise in optical
density (O.D.) lasting 10-20 sec, a phase of decreasing O.D. (5 min), pointing to
platelet aggregation and a phase of disaggregation afterwards. The samples of the
myocardial patients differed clearly in several aspects : in most of them (18) the
initial rise in O.D. was absent and aggregation started immediately; it was though
slower but reached a greater extent. The time of maximum aggregation was significantly
greater in the patients and there was no overlap with the controls. Coarse aggregates
were clearly visible. Final disaggregation was either minimal or absent. At a concen
tration of A.D.P. 0.59 γ/ml, the aggregation curve was biphasic in most patients,
whereas it was monophasic in the controls. The curves obtained were mathematically
analysed including the definition of a parameter called “aggregation time”, τ, and
an attempt was made to clarify several of the properties of the curves in terms of
platelet behaviour.
