CHRONIC PLATELET ACTIVATION AND ACUTE CORONARY SYNDROMES IN 13 MIDDLE-AGED PATIENTS

We report on clinical, laboratory, and angiographic findings that appe ar to characterize a group of 13 middle-aged patients who suffered acu te coronary syndromes (ACS) despite little angiographic evidence of at herosclerotic heart disease (ASHD) or other risk factors, Nine of the 13 were less than or equal to 46 years of age and the rest ranged to 5 9 years. All had evidence of platelet disorders (PD): seven had chroni c immune thrombocytopenia (ITP), one had familial thrombocytopenia, an d five had other disorders affecting platelets, Evidence of long-stand ing chronic platelet activation was the common feature of the group, a s found by (i) elevated platelet microparticles (PMP), (ii) thrombocyt openia. and (iii) enhanced procoagulant activity of plasma. Data on th e 7 with ITP were compared to 20 ITP without ACS: the former had highe r PMP (p < 0.01) and platelet-associated IgM (p < 0.05) relative to th e ITP patient controls, Another set of patient controls consisted of 2 0 ACS with documented ASHD: although activation indicators were abnorm al also in this group relative to normal controls (p < 0.01), the PB g roup of 13 had more marked abnormalities in all tests (p < 0.03), part icularly in PMP and thrombocytopenia (p < 0.01). The seven youngest in the PD group appeared to respond to antiplatelet therapy since no rec urrence of coronary ischemia was seen in up tit 3 years of observation , It is suggested that chronic platelet activation by antibodies ol im mune complex may predispose those in the PD group to ACS (e.g., when t inder stress) despite the absence of ASHD and few other known risk fac tors, The true incidence of this syndrome is unknown but may be substa ntial.