Surface 12-Lead Electrocardiographic Findings and Plasma Markers of Thrombin Activity and Generation in Patients with Myocardial Ischemia at Rest

ImpaCt of aspirin regimen on THrombin generation in diabEtic patients with acute coronary syndrome: CARTHaGE-ACS trial

BACKGROUND

Diabetes is associated with a high rate of events after acute coronary syndrome. It was recently reported that once-daily aspirin might not provide stable biological efficacy in patients with diabetes.

AIMS

We sought to compare the biological efficacy of aspirin given once a day versus aspirin divided twice per day in a population of diabetic patients with non-ST elevation acute coronary syndrome (NSTE-ACS) as assessed by the thrombin generation test.

METHODS

We performed an open-label single-blind randomized study including 59 consecutive diabetic patients admitted for NSTE-ACS. Patients were randomly treated with aspirin 100 mg once a day (GA100; n = 20), aspirin 160 mg once a day (GA160; n = 19) or aspirin 100 mg twice a day (G2A100; n = 20). The primary endpoint was endogenous thrombin potential (ETP) at discharge and after 6 months.

RESULTS

The mean age of our patients was 61.5 ± 9 years, and 73% were male. The baseline characteristics were comparable between the three groups. In the GA100 group, there was no significant effect on ETP variation at 6 months (1150.46 ± 504.84 vs. 1087.63 ± 454.18; p = 0.794). An increase in aspirin dose with a second daily administration of 100 mg was associated with a significant reduction in ETP at 6 months (1004.87 ± 196.2 vs. 1233.63 ± 333.5; p = 0.003). A nonsignificant decrease in ETP was seen in the GA160 group (from 1173.8 ± 388.07 to 1053.64 ± 269.93 at 6 months, p = 0.117).

CONCLUSION

Only the twice-daily aspirin regimen led to better control of hypercoagulability in NSTE-ACS diabetic patients. However, no thrombin generation normalization was reported.

Comparative effects of unfractionated heparin and low molecular weight heparin on vascular endothelial cell tissue factor pathway inhibitor release: a model for assessing intrinsic thromboresistance

OBJECTIVES

The purpose of our study was to characterize tissue factor pathway inhibitor (TFPI) release from human vascular endothelial cells following daily exposure to varying concentrations of unfractionated heparin (UFH) and low molecular weight heparin (LMWH).

BACKGROUND

A "rebound" increase in ischemic/thrombotic events, including myocardial infarction and cardiovascular death, has been observed after the abrupt cessation of UFH. In a single center pilot study of patients with acute coronary syndromes (ACS) we reported that thrombin generation was evident within one (1) hour of UFH cessation, increased progressively over the subsequent 24 hours, correlated directly with factor VII activity and inversely with TFPI (concentration and activity).

METHODS

Human umbilical vein endothelial cells were grown to confluence and incubated with varying concentrations of UFH or dalteparin, a low molecular weight haparin, for up to 144 hours. Daily samples of the cells supernatant were obtained and assayed for TFPI. Cellular reserve and responsiveness to recombinant endothelial cell growth factor (rEGF) stimulation were determined at 168 hours.

RESULTS

In low concentrations (0.5 U/mL) UFH caused a progressive rise in TFPI concentration with a peak level of 6.36 +/- 0.5 ng/10(5) cells at 24 hours. By 72 hours of daily exposure, the levels declined to below control values and TFPI release following rEGF stimulation was reduced by approximately 60% compared to control (1.93 +/- 0.42 vs 4.3 +/- 0.78 ng/10(5) cells; p = 0.001). Initial endothelial cell release and rate of decline were more robust with high concentrations of UFH (5.0 U/ml). TFPI levels were above control values at each sampling time point up to 120 hours and cellular responsiveness to stimulation was preserved with dalteparin (compared to UFH) (p < 0.001).

CONCLUSIONS

Thrombin generation and clinical events that occur during treatment with UFH and following its abrupt cessation may represent an acquired state of transiently impaired thromboresistance to the tissue factor-VIIa complex. The differing effects of UFH and LMWH on vascular endothelial cell TFPI synthesis, release and reserve with prolonged administration require further investigation.

Plasma Markers of Procoagulant Activity Among Individuals with Coronary Artery Disease

Background: There is compelling evidence that coronary atherosclerosis represents a chronic active process characterized by inflammation, impaired fibrinolysis, intermittent plaque rupture, and luminal thrombosis. Identifying readily measurable plasma markers of procoagulant activity may have an important role in both tracking and understanding the natural history, as well as in defining the ideal treatment, of patients with coronary artery disease. Methods/Results: A total of 30 men and women with suspected coronary artery disease who underwent outpatient cardiac catheterization were sampled for evidence of thrombin generation and fibrin formation in plasma. Compared with healthy controls, patients had significantly increased concentrations of fibrinopeptide A (18.8 +/- 10.8 ng/ml vs. 2.5 +/- 2.3, p < 0.001), thrombin-antithrombin complexes (8.13 +/- 4.56 ng/ml vs. 3.4 +/- 3.0, p < 0.001), and prothrombin activation fragment 1.2 (0.15 +/- 0.09 ng/ml vs. 0.12 +/- 0.19, p = 0.01). There was a statistically insignificant trend toward increased thrombin-antithrombin complex concentrations in patients with hypercholesterolemia (p = 0.10). Patients with angiographically defined coronary artery disease involving two or more vessels were found to have heightened thrombin generation and fibrin formation compared with those with single vessel disease. Conclusions: Patients with atherosclerotic coronary artery disease exhibit evidence of heightened procoagulant activity, including thrombin generation and fibrin formation. This observation, coupled with those derived from other recent studies, support the hypothesis that coronary atherosclerosis represents a chronic active process typified by vessel wall inflammation and recurrent thrombosis. Future efforts in disease prevention and treatment must consider these fundamental pathobiologic properties.

Thrombin: Structure, Biochemistry, Measurement, and Status in Clinical Medicine

Thrombin remains a molecule of great interest to scientists and clinicians alike because of its important role in hemostasis, thrombosis, inflammation and vascular remodeling. Yet one of the great challenges has been the inhibition of thrombin generation to a degree that minimizes intravascular thrombosis while preserving physiologic hemostasis. It has become increasingly clear that high levels of anticoagulation with either direct or indirect thrombin antagonists are not beneficial and, in fact, are quite detrimental. Despite the overwhelming shift of interest toward the platelet in clinical trials of acute coronary syndromes, much can be gained through further investigation of coagulation processes responsible for thrombin generation and activity.