Adenosine diphosphate-induced platelet aggregation of hospitalized men

Evaluation of platelet reactivity in diabetes mellitus

Seventeen patients with insulin-dependent diabetes mellitus, all below the age of 45 years, were studied. Five of them had retinopathy but no other micro- or macrovascular diabetic complications. None of them had any other concurrent disorder or were on any medication but insulin. The results were compared to those of 17 healthy volunteers of comparable age. There was no difference between the two groups in venous platelet counts, serum production of thromboxane B2 (TXB2), ADP-induced platelet aggregation or bleeding times. As compared to the controls, the diabetics had significantly elevated blood glucose and glycosylated hemoglobin values. The mean plasma values of beta-thromboglobulin, platelet factor 4 and TXB2 were significantly lower in the patients than in the controls. Thus, our results do not lend support to the current concept that platelet reactivity is enhanced in diabetes mellitus.

Effect of glucose on plasma concentrations of individual non-esterified fatty acids of non-diabetic and insulin-independent diabetic men

The composition of plasma non-esterified fatty acids was investigated during glucose tolerance tests to determine changes in individual fatty acid concentrations after glucose administration and to determine whether differences existed between the individual fatty acid concentrations of maturity-onset diabetic and non-diabetic men. The mean fasting total non-esterified fatty acid concentration of the 9 diabetics was greater than that of the 12 non-diabetics studied. After glucose ingestion, the mean total non-esterified fatty acid concentrations of both groups decreased. Gas chromatographic analysis of the plasma non-esterified fatty acids of 6 diabetic and 6 non-diabetic men revealed that the concentrations of palmitic, stearic and oleic acids were significantly higher in the diabetic men in the fasting state. With the sole exception of stearic acid in the non-diabetic patients, the mean concentration of each of the 6 plasma non-esterified fatty acids determined decreased in both groups after glucose ingestion. At 1, 2 and 3 hr after glucose ingestion, there were no longer any significant differences between the mean concentrations of individual plasma non-esterified fatty acids of the non-diabetic and diabetic men.

The hypercoagulability states

Although interest in coagulation has usually centered about the various hemorraghic disorders, it is hyperactivity of the hemostatic system with its thrombotic complications which has a far greater clinical impact. The hypercoagulability states are a vague group of disorders not well defined by the laboratory. They fall into two distinct groups: (1) conditions promoting venous thrombosis by activating the coagulation mechanism and (2) conditions promoting arterial thrombosis by platelet plug formation. Dealing with both of these groups separately the various disorders associated with a hypercoagulable state are discussed as well as their pathophysiologic basis; Special emphasis is placed on the laboratory evaluation of these disorders.

Peripheral venous platelet aggregates in patients with unstable angina pectoris and acute myocardial infarction

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.