Peripheral Venous Platelet Aggregates in Patients With Unstable Angina Pectoris and Acute Myocardial Infarction

Abstract

In vivo peripheral venous platelet aggregates (PVPA) have been demon strated in patients with myocardial infarction (MI), transient cerebral ischemic attacks (TIAs), and acute arterial insufficiency by the platelet count ratio (PCR) method. But PVPA determinations have not been reported in patients with unstable angina pectoris (UA), controls have not been specified as acutely ill in earlier studies using this technique, and variability of the method has not been presented in detail. Because platelet aggregation has been mentioned as a possible mechanism for perpetuating myocardial ischemia, we studied 21 acutely ill noncardiac control (NC) patients, 17 UA patients, and 13 MI patients for PVPA.

PCR represents ratio of platelet counts obtained when identical aliquots of blood were drawn into two syringes containing formalin-EDTA and EDTA respectively. Free flow was demonstrated before blood was drawn. Mean PCR was 0.90 ± 0.01 (SE) in NC, 0.85 ± 0.02 in UA, and 0.85 ± 0.02 in MI. In the subset of 7 patients with acute transmural MI, PCR was 0.83 ± 0.02. Only this subset was significantly different from NC (P < 0.001). PCR did not vary significantly with age or sex. Aspirin history was positive in 25-30% of the patients in each group and raised PCR by an average of 0.04 units. When PCR was repeated after 45 minutes in 6 patients, moderate variability with a mean absolute change in PCR of 0.08 was noted.

Our data fail to support an etiologic role for circulating platelet aggre gates in initiating UA. Clinical trials of platelet inhibitors and experimen tal models of arterial insufficiency probably offer the greatest chance of further defining the potential etiologic role of platelet aggregation in initiating or perpetuating myocardial ischemic phenomena.

References

Frishman, W.H. , Weksler, B. , Christodoulou, J.P. , et al.: Reversal of abnormal platelet aggregability and change in exercise tolerance in patients with angina pectoris following oral propranolol. Circulation, 50: 887, 1974.

Steele, P.P. , Weily, H.S. , Davies, H. , et al.: Platelet function studies in coronary artery disease. Circulation, 48: 1194, 1973 .

Ritchie, J.L. , Harker, L.A. : Platelet, fibrinogen, and plasminogen survival in patients with coronary artery disease. Circulation, 50: 285, 1974 (abstr., suppl. 3).

Salky, N. , Dugdale, M. : Platelet abnormalities in ischemic heart disease. Am. J. Cardiol. , 32: 612, 1973.

Fleisehman, A.I. , Bierenbaum, M.L. , Justice, D. , et al.: In vivo platelet function in acute myocardial infarction, acute cerebrovascular accidents and following surgery . Thrombosis Res., 6: 205, 1975.

Wu, K.K. , Hoak, J.C. : A new method for the quantitative detection of platelet aggregates in patients with arterial insufficiency. Lancet, 2: 924, 1974.

Gordon, J.L. , Bowyer, D.E. , Evans, D.W. , et al.: Human platelet reactivity during stressful diagnostic procedures. J. Clin. Pathol., 26: 958, 1973.

Haft, J.I. , Arkel, Y.S. : Effect of emotional stress on platelet aggregation in humans. Clin. Res., 23: 186A, 1975 (abstr.).

Davis, J.W. , Yue, K.T.N. , Phillips, P.E. , et al.: Adenosine diphosphate-induced platelet aggregation of hospitalized men. Scand. J. Haematol., 13: 17, 1974.

10.

Hampton, J.R. , Harrison, M.T.G. , Honour, A.J. , et al.: Platelet behaviour and drugs used in cardiovascular disease. Cardiovasc. Res., 1: 101, 1967.

11.

Wu, K.K. , Hoak, J.C. : Increased platelet aggregates in patients with transient ischemic attacks. Stroke, 6: 521, 1975.

12.

Mustard, J.F. , Packham, M.A. : The role of blood and platelets in atherosclerosis and the complications of atherosclerosis. Thromb. Diath. Haemorrh. , 33: 444, 1975.

13.

Stein, P.D. , Sabbah, H.N. : Turbulent blood flow and thrombosis. Circulation, 50: 295, 1974 (abstr., suppl. 3).

14.

Haft, J.I. , Gershengorn, K. , Kranz, P. , et al.: Protection against epinephrine-induced myocardial necrosis by drugs that inhibit platelet aggregation. Am. J. Cardiol. , 30: 838, 1972.

15.

Jorgenson, L. , Rowsell, H.C. , Hovig, T. , et al.: Adenosine diphosphate-induced platelet aggregation and myocardial infarction in swine. Lab. Invest. , 17: 616, 1967.

16.

Frishman, W. , Christodoulou, J. , Weksler, B. , et al.: Aspirin therapy in angina pectoris: Effects on exercise tolerance, pain threshold, and platelet aggregability . Am. J. Cardiol., 35: 137, 1975 (abstr.).

17.

Donsky, M.S. , Curry, G.C. , Parkey, R.W. , et al.: Unstable angina pectoris: Clinical, angiographic, and myocardial scintigraphic observations. Br. Heart J., 38: 257, 1976.

18.

Folts, J.D. , Crowell, E.B. , Rowe, G.G. : Platelet aggregation in partially obstructed vessels and its elimination with aspirin. Circulation, 54: 365, 1976.