Thrombin generation in patients with a first acute myocardial infarction.

BACKGROUND: Despite improved treatment options, myocardial infarction is still an important cause of morbidity and mortality. One of the contributing mechanisms in the acute myocardial infarction (AMI) is plasma hypercoagulability. METHODS: We investigated hypercoagulability in 135 (first) patients with AMI using thrombin generation (TG) testing. TG testing was performed in plasmas, drawn upon admission and before medication administration, and subsequently after 4 days, 3 and 6 months. Further, we evaluated determinants of thrombin generation using multiple regression analysis of major coagulation proteins and inhibitors. Admission TG results were also related to 1-year outcome: cardiovascular death, recurrent myocardial infarction, a second coronary intervention [percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG)] and ischemic stroke. RESULTS: At day 0, the TG parameters peak height, endogenous thrombin potential (ETP) and lag time were increased compared with a reference population. Peak height and lag time stayed persistently increased in patients. The lowest half of the ETP values was statistically not significantly associated with an occurrence of endpoints. The lowest half of the ETP values combined with the upper half of the D-dimer values were associated with endpoints; odds ratio 5.8 (1.1-30.7). Tissue factor pathway inhibitor (TFPI) seems to be an important determinant of TG in AMI and healthy persons. CONCLUSIONS: TG reflects acute hypercoagulability during AMI and partly also in the 6-month period after the acute event. TG shows a trend of an inverse association with risk of recurrent ischemic cardiovascular complications. Unraveling mechanisms in TG might improve our understanding of the pathophysiology of AMI and direct future improvements in medical care.

Coagulation factors and the protein C system as determinants of thrombin generation in a normal population.

BACKGROUND: Thrombin generation is a powerful tool to probe overall plasma coagulability. OBJECTIVE: To determine which plasma factors influence the various parameters of the thrombin generation curve, for example lag time, peak height and endogenous thrombin potential (ETP), under different experimental conditions. PATIENTS AND METHODS: Plasma levels of coagulation factors and inhibitors, as well as thrombin generation at 1 pm tissue factor (TF) +/- thrombomodulin (TM) and at 13.6 pm TF +/- activated protein C (APC), were determined in plasma from 140 healthy individuals. Data were analysed by multiple regression models. RESULTS: Thrombin generation increased with age and was higher in females than in males. Under all conditions, the lag time was mainly dependent on the levels of free tissue factor pathway inhibitor (TFPI), free protein S (PS), factor VII (FVII), FIX and fibrinogen. The major determinants of thrombin generation (ETP and peak height) at 1 pm TF were fibrinogen, FXII (despite inhibition of contact activation), free TFPI and antithrombin (AT), both in the absence and in the presence of TM. Thrombin generation in the presence of TM was also dependent on protein C levels. At 13.6 pm TF, thrombin generation was determined by prothrombin, AT, fibrinogen, free TFPI and FV levels in the absence of APC, and by free TFPI, free PS and FX levels in the presence of APC. CONCLUSIONS: The lag time, ETP and peak height of thrombin generation depend on the levels of multiple coagulation factors and inhibitors. The specific assay determinants vary with the experimental conditions.

Changes in fibrinolytic activity after angiotensin II receptor blockade in therapy-resistant hypertensive patients.

BACKGROUND: In hypertensive patients, the activated renin-angiotensin system induces a prothrombotic state resulting from imbalance between coagulation and fibrinolysis. Although blood pressure cannot be regulated in therapy-resistant hypertensive patients, they may still be responsive to medication that attenuates the renin-angiotensin system. OBJECTIVE: our objective was to study possible attenuating properties of angiotensin II type 1 receptor blockers (AT1RBs) on the prothrombotic state in therapy-resistant hypertensive patients, focusing on parameters of fibrinolysis and coagulation. METHODS: Fourteen therapy-resistant hypertensive patients received AT1RB eprosartan infusion (45 and 150 microg kg(-1)) (study group), and 33 therapy-resistant hypertensive patients received saline (0.9%) infusion (control group) prior to renal angiography. Baseline values of parameters of coagulation and fibrinolysis were set at 1.00, and relative changes were calculated. RESULTS: Plasminogen activator inhibitor type 1 (PAI-1) antigen showed non-significant decreases in both the study group (arterial 1.00-0.45, venous 1.00-0.42) and control group (arterial 1.00-0.84, venous 1.00-0.88). PAI-1 activity significantly decreased in the study group (arterial 1.00-0.72, venous 1.00-0.71) and control group (arterial 1.00-0.83, venous 1.00-0.94). In the study group, tissue-type plasminogen activator (t-PA) antigen decreased significantly (arterial 1.00-0.62, venous 1.00-0.67), whereas t-PA activity significantly increased (arterial 1.00-6.15, venous 1.00-2.66). In the control group, t-PA antigen remained unchanged. No changes were observed in blood pressure during and after infusion of eprosartan. CONCLUSION: Therapy-resistant hypertensive patients show beneficial changes in fibrinolytic activity after infusion of a non-pressor dose of AT1RB.