Impaired thrombolytic status predicts adverse cardiac events in patients undergoing primary percutaneous coronary intervention

Assessment of endogenous fibrinolysis in clinical practice using novel tests: ready for clinical roll-out?

The occurrence of thrombotic complications, which can result in excess mortality and morbidity, represent an imbalance between the pro-thrombotic and fibrinolytic equilibrium. The mainstay treatment of these complications involves the use of antithrombotic agents but despite advances in pharmacotherapy, there remains a significant proportion of patients who continue to remain at risk. Endogenous fibrinolysis is a physiological counter-measure against lasting thrombosis and may be measured using several techniques to identify higher risk patients who may benefit from more aggressive pharmacotherapy. However, the assessment of the fibrinolytic system is not yet accepted into routine clinical practice. In this review, we will revisit the different methods of assessing endogenous fibrinolysis (factorial assays, turbidimetric lysis assays, viscoelastic and the global thrombosis tests), including the strengths, limitations, correlation to clinical outcomes of each method and how we might integrate the assessment of endogenous fibrinolysis into clinical practice in the future.

Fibrinolysis in Acute and Chronic Cardiovascular Disease

The formation of an obstructive thrombus within an artery remains a major cause of mortality and morbidity worldwide. Despite effective inhibition of platelet function by modern antiplatelet therapies, these agents fail to fully eliminate atherothrombotic risk. This may well be related to extensive vascular disease, beyond the protective abilities of the treatment agents used. However, recent evidence suggests that residual vascular risk in those treated with modern antiplatelet therapies is related, at least in part, to impaired fibrin clot lysis. In this review, we attempt to shed more light on the role of hypofibrinolysis in predisposition to arterial vascular events. We provide a brief overview of the coagulation system followed by addressing the role of impaired fibrin clot lysis in acute and chronic vascular conditions, including coronary artery, cerebrovascular, and peripheral vascular disease. We also discuss the role of combined anticoagulant and antiplatelet therapies to reduce the risk of arterial thrombotic events, addressing both efficacy and safety of such an approach. We conclude that impaired fibrin clot lysis appears to contribute to residual thrombosis risk in individuals with arterial disease on antiplatelet therapy, and targeting proteins in the fibrinolytic system represents a viable strategy to improve outcome in this population. Future work is required to refine the antithrombotic approach by modulating pathological abnormalities in the fibrinolytic system and tailoring therapy according to the need of each individual.

Frequency of Thrombolysis in Myocardial Infarction III Flow in Patients With Primary Percutaneous Coronary Intervention: Not All Culprit Vessels Are Completely Occluded in ST Elevation Myocardial Infarction

Background

ST elevation myocardial infarction (STEMI) is classically characterized by total occlusion of the culprit coronary artery. However during primary percutaneous coronary intervention (PCI) thrombolysis in myocardial infarction (TIMI) 0 flow is not observed in all patients' culprit arteries in angiographic views. This study was conducted to find out the frequency of TIMI flow in acute STEMI patients in view of the above concept. The aim of this study was to evaluate the frequency of pre-procedural TIMI III flow in those patients who underwent primary PCI for acute STEMI in a public sector hospital in Karachi, Pakistan.

Methodology

This study is an audit of already saved data in the catheterization laboratory of the National Institute of Cardiovascular Diseases (NICVD), Karachi, that was collected prospectively from January 2016 to December 2018. These data were collected after taking consent from those patients who presented to hospital within 12 hours of symptoms and underwent primary PCI. Data were entered and analyzed on Statistical Package for the Social Sciences (SPSS) version 19 (IBM Corp., Armonk, NY, USA).

Results

A total of 8018 patients were included in this study who presented with STEMI and underwent primary PCI. Out of them 80.9% were males. Hypertension was the leading risk factor in 54.1% (4340) of patients. TIMI III flow was present in 11.4% of patients before primary PCI, while TIMI 0, I and II flow were present in 57.1%, 15.1%, and 16.3% of patients respectively (p<0.001). Fourteen percent of patients with TIMI III flow were of age group 51 to 60 years. Among those who had TIMI III flow, 11.2% were those with door to balloon time of <90 minutes. In 11% of cases, left anterior descending (LAD) artery had TIMI III flow as compared to other vessels (p<0.001). The length of the lesion was significantly smaller in patients who had TIMI III flow compared to those who had TIMI 0-II flow.

Conclusions

This study revealed that not all patients with acute STEMI had totally occluded culprit coronary artery but some of them had angiographic TIMI I-III flow in the infarct-related artery. Further studies are needed to find the reason for re-establishment of flow in the culprit vessel in STEMI patients before PCI.

Serum apelin predicts spontaneous reperfusion of infarct-related artery in patients with ST-segment elevation myocardial infarction

BACKGROUND

Spontaneous reperfusion (SR) was associated with significant myocardial salvage, decreased mortality rates, better clinical outcomes, and lower incidences of major adverse cardiovascular events. It was found that apelin inhibited thrombin-induced and collagen-induced platelet activation and aggregation. This study was carried out to assess whether serum apelin correlates with SR of the infarct-related coronary artery in ST-elevation myocardial infarction (STEMI) patients.

PATIENTS AND METHODS

Blood samples were obtained on admission in 280 consecutive patients with STEMI before primary percutaneous coronary intervention. Blood chemistry and apelin levels were tested. Coronary arteriography and echocardiography were performed after admission.

RESULTS

Frequencies of the patients with preinfarct angina, history of smoking, and pathoglycemia were higher in the non-SR group than in the SR group (P=0.03, 0.001, and 0.002, respectively). Peak values of plasma troponin-I and frequencies of the patients with Killip 2-3 were significantly higher in the non-SR group (P<0.05, respectively) compared with the SR group. Left ventricular systolic and diastolic functions improved markedly in the SR group compared with the non-SR group. Gensini scores were lower in the SR group than the non-SR group (P=0.02). Serum apelin was significantly higher in patients with SR compared with patients with non-SR (0.82±0.34 vs. 0.35±0.22 ng/ml, P=0.04). A cut-off value of 0.75 ng/ml had a predictive value of 77% to identify patients with SR. In the non-SR group, patients who died in the hospital had much lower apelin levels compared with those who survived (P<0.001). Apelin level in the high thrombus load group was much lower compared with the other group (P<0.001). Apelin level in the group undergoing successful reperfusion was much higher than that in the group without successful reperfusion (P<0.001).

CONCLUSION

Patients with SR have better cardiac systolic function and improved diastolic function. An increased serum apelin level is an independent and novel predictor of SR for STEMI patients.

High-throughput targeted proteomics discovery approach and spontaneous reperfusion in ST-segment elevation myocardial infarction

BACKGROUND

Although spontaneous reperfusion (SR) prior to primary percutaneous coronary intervention (pPCI) is associated with improved outcomes, its pathophysiology remains unclear. The objective of the study was to explore associations between SR in ST-segment elevation myocardial infarction (STEMI) using a multimarker cardiovascular proteins strategy METHODS: We evaluated STEMI patients from the Assessment of Pexelizumab in Acute Myocardial Infarction trial treated with pPCI within 6 hours from symptom onset. SR was core laboratory-defined as pre-PCI Thrombolysis in Myocardial Infarction flow 2 or 3. Ninety-one cardiovascular disease-related serum biomarkers drawn prior to PCI were analyzed using a high-throughput "targeted discovery" panel. Expression levels for individual biomarkers were compared between patients with/without SR. A hierarchical clustering method of biomarkers identified clusters of biomarkers that differentiated the 2 groups. Associations between individual biomarkers and clusters with SR were further evaluated by multivariable logistic regression.

RESULTS

Of 683 patients studied, 290 had spontaneous reperfusion; those with compared to without SR were more likely noninferior STEMI and had lower clinical acuity and lower baseline levels of troponin and creatine kinase. SR was associated with a lower occurrence of 90-day composite of death, heart failure, or cardiogenic shock. Fifty-two of 91 individual biomarkers were significantly univariably associated with SR. Forty-five remained significant with adjustment for false discovery rate. Using cluster analysis, 26 biomarkers clusters were identified, explaining 72% of total covariance, and 13 biomarker clusters were significantly associated with SR after multivariable adjustment. SR was associated with higher mean expression levels of proteins in all 13 clusters. The cluster most strongly associated with SR consisted of novel proteins across various distinct, yet interlinked, pathobiological processes (kallikrein-6, matrix extracellular phosphoglycoprotein, matrix mettaloproteinaise-3, and elafin).

CONCLUSIONS

Spontaneous reperfusion prior to pPCI in STEMI was associated with a lower risk of adverse clinical events. These exploratory data from a targeted discovery proteomics platform identifies novel proteins across diverse, yet complementary, pathobiological axes that show promise in providing mechanistic insights into spontaneous reperfusion in STEMI.

CONDENSED ABSTRACT

Spontaneous reperfusion has been established with improved STEMI outcomes, yet its pathobiology is unclear and appears to involve diverse physiological processes. Using a 91-biomarker high-throughput proteomics platform, we studied 683 STEMI patients in the APEX AMI trial (290 had core laboratory-adjudicated pre-PCI TIMI 2/3 flow) and identified 52 proteins that univariably associate with spontaneous reperfusion. Cluster analysis identified 26 biomarker clusters (explaining 72% of total variance), 13 of which, after multivariable adjustment, were significantly associated with spontaneous reperfusion. Four proteins (kallikrein-6, matrix extracellular phosphoglycoprotein, matrix mettaloproteinaise-3, and elafin) across diverse, yet complementary, pathways appear to be associated most strongly with spontaneous reperfusion.

Fibrin clot properties independently predict adverse clinical outcome following acute coronary syndrome: a PLATO substudy

Aims

To determine whether fibrin clot properties are associated with clinical outcomes following acute coronary syndrome (ACS).

Methods and results

Plasma samples were collected at hospital discharge from 4354 ACS patients randomized to clopidogrel or ticagrelor in the PLATelet inhibition and patient Outcomes (PLATO) trial. A validated turbidimetric assay was employed to study plasma clot lysis time and maximum turbidity (a measure of clot density). One-year rates of cardiovascular (CV) death, spontaneous myocardial infarction (MI) and PLATO-defined major bleeding events were assessed after sample collection. Hazard ratios (HRs) were estimated using Cox proportional hazards models. After adjusting for CV risk factors, each 50% increase in lysis time was associated with CV death/spontaneous MI [HR 1.17, 95% confidence interval (CI) 1.05-1.31; P < 0.01] and CV death alone (HR 1.36, 95% CI 1.17-1.59; P < 0.001). Similarly, each 50% increase in maximum turbidity was associated with increased risk of CV death (HR 1.24, 95% CI 1.03-1.50; P = 0.024). After adjustment for other prognostic biomarkers (leukocyte count, high-sensitivity C-reactive protein, high-sensitivity troponin T, cystatin C, N-terminal pro B-type natriuretic peptide, and growth differentiation factor-15), the association with CV death remained significant for lysis time (HR 1.2, 95% CI 1.01-1.42; P = 0.042) but not for maximum turbidity. These associations were consistent regardless of randomized antiplatelet treatment (all interaction P > 0.05). Neither lysis time nor maximum turbidity was associated with major bleeding events.

Conclusion

Fibrin clots that are resistant to lysis independently predict adverse outcome in ACS patients. Novel therapies targeting fibrin clot properties might be a new avenue for improving prognosis in patients with ACS.

Impaired endogenous fibrinolysis at high shear using a point-of-care test in STEMI is associated with alterations in clot architecture

Impaired endogenous fibrinolysis is an adverse prognostic biomarker in acute coronary syndrome (ACS). Abnormally dense in vitro fibrin thrombi have been demonstrated in ACS patients and related to hypofibrinolysis using cumbersome, laboratory-based methods. We aimed to assess endogenous fibrinolysis using a point-of-care technique and relate this to clot architecture. From patients with ST-segment elevation myocardial infarction (STEMI), venous blood was drawn immediately on arrival to assess thrombotic status. Blood was assessed using the point-of-care Global Thrombosis Test which measures occlusive thrombus formation under high shear and subsequently endogenous fibrinolysis (lysis time, LT). Two samples per patient were run in parallel. In one channel, the measurement was allowed to proceed as normal. In the other, after occlusion, thrombus was extracted, washed, fixed in glutaraldehyde, dried, sputter-coated, and assessed using scanning electron microscope. Endogenous fibrinolysis was strongly associated fibrin fibre thickness (p = 0.0001). As LT increased (less efficient fibrinolysis), the fibrin network of the thrombus was significantly more compact and dense, with thinner fibrin fibres and smaller gaps. Fibrin fibre thickness correlated inversely with LT (r = − 0.89, p = 0.001). Adverse clot architecture in vitro is directly related to impaired endogenous fibrinolysis using a relatively new point-of-care technique in patients with STEMI. This may transform the relevance of fibrin clot architecture from an off-line laboratory association to being directly relevant to endogenous fibrinolysis at the patient bedside, which could be used as a near-patient test to guide prognosis and assess the effect of treatment.

Recent advances in microfluidic platelet function assays: Moving microfluidics into clinical applications

The analysis of platelet aggregation and thrombosis kinetics has significantly advanced with progress in microfluidic technology. However, the results of platelet aggregation tests do not fully reflect the observed clinical outcomes. To address the present unmet clinical needs, the basic but essential biology of platelets should be reconsidered in relation to the characteristics of microfluidic systems employed for platelet tests. To this end, the present article provides an overview of commercially available point of care devices and focuses on recent microfluidic studies, describing their measurement principles. We critically discuss the characteristics of the microfluidics systems used to evaluate the complex processes underlying platelet aggregation, and that are specifically designed to mimic the pathophysiological environment of blood vessels, including hemodynamic factors as well as blood vessel injury. To this end, we summarize unsolved issues related to the application of platelet function tests based on microfluidics. Overall, we confirm that platelet function tests based on microfluidics provide a versatile platform that encompasses a variety of basic research, as well as clinical diagnostic applications.

Admission homocysteine is an independent predictor of spontaneous reperfusion and early infarct-related artery patency before primary percutaneous coronary intervention in ST-segment elevation myocardial infarction

Background

Spontaneous reperfusion (SR) and early infarct related artery (IRA) patency before primary percutaneous coronary intervention (PPCI) might bring extra benefit for patients with ST-segment elevation myocardial infarction (STEMI). This study premilinarily screened the independent predictors of SR, and assessed the relationship between SR and plasma homocysteine (HCY).

Methods

The medical records of 998 patients who were diagnosed as STEMI and underwent emergency coronary angiography were retrospectively studied, SR was defined as achievement of TIMI grade 3 flow in the IRA before PCI. The baseline characteristics, clinical manifestations and hematological variables were compared between SR and NSR group. Optimal cutoff point of HCY was calculated with receiving operating characteristics (ROC) analysis, multivariate logistic regression models were used to identify predictors of SR.

Results

229 (22.95%) patients showed angiographic SR. For HCY, the area under the curve was 0.70 (95% CI: 0.63–0.77, P = 0.034), the optimized cut off point was 17.55 μmol/L. Preinfarct angina (95% CI: 1.61–5.65, P = 0.0005), plasma C-reactive protein (CRP) level (95% CI: 0.87–0.99, P = 0.016) and HCY < 17.55 μmol/L (95% CI: 2.43–8.72, P < 0.0001) were found to be independent predictors for SR.

Conclusion

In patients with STEMI, HCY < 17.55 μmol/L, preinfarct angina and plasma CRP level were independent predictors of SR.

Prevention of thrombotic disorders by antithrombotic diet and exercise: evidence by using global thrombosis tests

Prevention of thrombotic disorders has priority over treatment. There are only two pathologically relevant tests which are suitable for measuring the overall thrombotic status both in experimental conditions and in humans. The Global Thrombosis Test (GTT) and the Global Parallel-Plate Thrombosis Test can detect the pathologically relevant global thrombotic status. These tests have been successfully used for monitoring the effect of antithrombotic drugs and for developing novel antithrombotic agents. By using GTT, varieties of fruits, vegetables, and regular physical exercise have been tested for the effect on global thrombotic status. This review discusses the published evidence for the benefit of diet of selected fruit and vegetable varieties and doing regular physical exercise on improving thrombotic status. Future clinical trials monitored by GTT or Global Parallel-Plate Thrombosis Test could decide on the effectiveness of an experimentally proven antithrombotic diet with regular physical exercise in the prevention of thrombotic diseases.

Importance of Endogenous Fibrinolysis in Platelet Thrombus Formation

The processes of thrombosis and coagulation are finely regulated by endogenous fibrinolysis maintaining healthy equilibrium. When the balance is altered in favour of platelet activation and/or coagulation, or if endogenous fibrinolysis becomes less efficient, pathological thrombosis can occur. Arterial thrombosis remains a major cause of morbidity and mortality in the world despite advances in medical therapies. The role endogenous fibrinolysis in the pathogenesis of arterial thrombosis has gained increasing attention in recent years as it presents novel ways to prevent and treat existing diseases. In this review article, we discuss the role of endogenous fibrinolysis in platelet thrombus formation, methods of measurement of fibrinolytic activity, its role in predicting cardiovascular diseases and clinical outcomes and future directions.