Role of Thrombelastography (TEG) in Risk Assessment and Guidance of Antithrombotic Therapy in Patients with Coronary Artery Disease

Material strengths of shear-induced platelet aggregation clots and coagulation clots

Arterial occlusion by thrombosis is the immediate cause of some strokes, heart attacks, and peripheral artery disease. Most prior studies assume that coagulation creates the thrombus. However, a contradiction arises as whole blood (WB) clots from coagulation are too weak to stop arterial blood pressures (> 150 mmHg). We measure the material mechanical properties of elasticity and ultimate strength for Shear-Induced Platelet Aggregation (SIPA) type clots, that form under stenotic arterial hemodynamics in comparison with coagulation clots. The ultimate strength of SIPA clots averaged 4.6 ± 1.3 kPa, while WB coagulation clots had a strength of 0.63 ± 0.3 kPa (p < 0.05). The elastic modulus of SIPA clots was 3.8 ± 1.5 kPa at 1 Hz and 0.5 mm displacement, or 2.8 times higher than WB coagulation clots (1.3 ± 1.2 kPa, p < 0.0001). This study shows that the SIPA thrombi, formed quickly under high shear hemodynamics, is seven-fold stronger and three-fold stiffer compared to WB coagulation clots. A force balance calculation shows a SIPA clot has the strength to resist arterial pressure with a short length of less than 2 mm, consistent with coronary pathology.

Prevalence and impact of fibrinolytic dysregulation in patients with acute coronary syndromes

Objective

Dual antiplatelet therapy can reduce coronary thrombosis and improve the prognosis in patients with acute coronary syndrome (ACS). However, there was limited prognostic information about fibrinolytic dysregulation in patients with ACS. This study is aimed to evaluated the prevalence and impact of fibrinolytic dysregulation in patients with acute coronary syndrome (ACS).

Methods

We retrospectively analyzed coagulation and fibrinolysis related indexes of ACS in hospitalized adults with rapid thrombelastography between May 2016 and December 2018. All of the follow-up visits were ended by December 2019. The primary outcome was the occurrence of major adverse cardiovascular events (MACEs), which included unstable angina pectoris, non-fatal myocardial infarction, non-fatal cerebral infarction, heart failure and all-cause death.

Results

Three hundred thirty-eight patients were finally included with an average age of 62.5 ± 12.8 years old, 273 (80.5%) were males, 137(40.5%) patients were with ST-elevation myocardial infraction. Fibrinolysis shutdown (LY30<0.8%) and hyperfibrinolysis (LY30 >3.0%) were observed among 163 (48.2%) and 76(22.5%) patients, respectively. During a total of 603.2 person·years of follow-up period, 77 MACEs occurred (22.8%). Multivariate Cox regression analysis indicated that LY30 [HR: 1.101, 95% CI: 1.010–1.200, P = 0.028] was independently correlated with the occurrence of MACEs. The hazard ratios pertaining to MACEs in patients with fibrinolysis shutdown and hyperfibrinolysis compared with those in the physiologic range (LY30: 0.8–3.0%) were 1.196 [HR: 1.196, 95% CI: 0.679–2.109,P = 0.535] and 2.275 [HR: 2.275, 95% CI: 1.241–4.172, P = 0.003], respectively.

Conclusions

Fibrinolytic dysregulation is very common in selected patients with ACS, and hyperfibrinolysis (LY30 > 3%) is associated with poor outcomes in patients with ACS.

A Preclinical Porcine Model of Portal Vein Thrombosis in Liver Cirrhosis

Background

This study aimed at presenting a novel method of developing a porcine model of portal vein thrombosis (PVT) in cirrhosis by intravenous administration of thrombin and insertion of a fibered coil. We further investigated changes of biochemical parameters, coagulation, and proinflammatory cytokine expression in the cirrhosis-PVT group.

Methods

Twelve male pigs were randomized into the control group (n = 3) and cirrhosis group (n = 9). In cirrhotic pigs, three were randomly selected to establish PVT by ultrasound-guided percutaneous puncture of the main portal vein (MPV) followed by intravenous thrombin administration and fibered coil insertion. Thrombosis in the MPV was detected by abdominal enhanced computer tomography (CT). The changes of hepatic function, coagulation system, and inflammation cytokines were compared among normal, cirrhosis, and cirrhosis with PVT groups.

Results

As manifested by the presence of a filling defect in MPV on portal venous-phase CT angiography, fibrin thrombi were formed in the MPV in cirrhotic pigs within one week and persisted for four weeks. Five weeks after surgery, abnormal liver functions occurred in association with PVT formation in cirrhosis. Both coagulation and thromboelastography parameters showed that cirrhosis-PVT pigs exhibited a procoagulant state through hyperfunction of platelets and clotting factors. Interleukin 6 (IL-6) as a potential inflammatory marker stimulated PVT-mediated inflammation activation in cirrhosis.

Conclusions

Our study provides in vivo evidence that intravenous injection of a coil and thrombin into MPV under interventional guided devices enables a feasible method in thrombus creation. Further exploration and validation of large-sample cases are required to characterize utilities of this model.

Fibrin Clot Strength in Patients with Diabetes Mellitus Measured by Thrombelastography

BACKGROUND

Patients with diabetes mellitus (DM) exhibit increased risk of recurrent myocardial infarction. Maximal clot strength measured by thrombelastography (TEG) is a risk factor for recurrent ischemic events. We hypothesized that diabetic subjects exhibit increased fibrin clot strength in platelet-poor plasma and that glycemic control correlates with maximal fibrin clot strength.

METHODS

We collected plasma samples from subjects with known or suspected coronary artery disease undergoing cardiac catheterization (n = 354). We measured kaolin-activated TEG in platelet-poor citrate plasma. Time to fibrin formation (R), clot formation time (K), and maximal fibrin clot strength (MA) were recorded.

RESULTS

Plasma fibrin MA was increased among subjects with DM (n = 152) as compared to non-DM (n = 202) (37.0 ± 8 versus 34.1 ± 8 mm; p < 0.001). Hemoglobin A1c (HbA1c) (ρ = 0.22; p = 0.001) and fibrinogen (ρ = 0.29; p < 0.001) correlated with fibrin MA. In multivariable regression analysis, DM remained significantly associated with plasma MA after adjustment for fibrinogen level (p = 0.003).

CONCLUSIONS

Subjects with diabetes mellitus exhibit increased maximal fibrin clot strength measured by TEG in platelet-poor plasma.

Fibrin clot strength measured by thrombelastography and outcomes after percutaneous coronary intervention

Supplementary Material to this article is available online at www.thrombosis-online.com.

Platelet factor XIIIa release during platelet aggregation and plasma clot strength measured by thrombelastography in patients with coronary artery disease treated with clopidogrel

It has been estimated that up to half of circulating factor XIIIa (FXIIIa) is stored in platelets. The release of FXIIIa from platelets upon stimulation with adenosine diphosphate (ADP) in patients with coronary artery disease treated with dual antiplatelet therapy has not been previously examined. Samples from 96 patients with established coronary artery disease treated with aspirin and clopidogrel were examined. Platelet aggregation was performed by light transmittance aggregometry in platelet-rich plasma (PRP), with platelet-poor plasma (PPP) as reference, and ADP 5 µM as agonist. Kaolin-activated thrombelastography (TEG) was performed in citrate PPP. PRP after aggregation was centrifuged and plasma supernatant (PSN) collected. FXIIIa was measured in PPP and PSN. Platelet aggregation after stimulation with ADP 5 µM resulted in 24% additional FXIIIa release in PSN as compared to PPP (99.3 ± 27 vs. 80.3 ± 24%, p < 0.0001). FXIIIa concentration in PSN correlated with maximal plasma clot strength (TEG-G) (r = 0.48, p < 0.0001), but not in PPP (r = 0.15, p = 0.14). Increasing quartiles of platelet-derived FXIIIa were associated with incrementally higher TEG-G (p = 0.012). FXIIIa release was similar between clopidogrel responders and non-responders (p = 0.18). In summary, platelets treated with aspirin and clopidogrel release a significant amount of FXIIIa upon aggregation by ADP. Platelet-derived FXIIIa may contribute to differences in plasma TEG-G, and thus, in part, provide a mechanistic explanation for high clot strength observed as a consequence of platelet activation. Variability in clopidogrel response does not significantly influence FXIIIa release from platelets.