Serum lipoprotein(a) level is related to thrombin generation and spontaneous intermittent coronary occlusion in patients with acute myocardial infarction

Very low lipoprotein(a) and increased mortality risk after myocardial infarction

BACKGROUND

Inconclusive data exist on risk associated with Lp(a) in patients after myocardial infarction (MI). Aims of the present study were to evaluate the association of Lp(a) level with total mortality and recurrent cardiovascular events.

DESIGN AND METHODS

Single center prospective registry of consecutive patients hospitalized for acute myocardial infarction between June 2017 and June 2020 at a large tertiary cardiac center with available blood samples drawn <24h of admission.

RESULTS

Data from 851 consecutive patients hospitalized for MI were evaluated. During the median follow-up of 19 months (interquartile range 10-27), 58 (6.8%) patients died. Nonlinear modelling revealed a U-shaped association between Lp(a) and total mortality risk. Compared to patients with Lp(a) ranging between 10-30 nmol/L and after multivariate adjustment, total mortality risk was increased both in patients with Lp(a)<7 nmol/L (hazard ratio (HR) 4.08, 95% confidence interval (CI) 1.72-9.68) and Lp(a) ≥125 nmol/L (HR 2.92, 95% CI 1.16-7.37), respectively. Similarly, the risk of combined endpoint of acute coronary syndrome recurrence or cardiovascular mortality was increased both in patients with low (sub-HR 2.60, 95% CI 1.33-5.08) and high (sub-HR 2.10, 95% CI 1.00-4.39) Lp(a). Adjustment for heart failure signs at the time of hospitalization weakened the association with total mortality and recurrent cardiovascular events.

CONCLUSIONS

In the present analysis, both high and low concentrations of Lp(a) were associated with an increased risk of total mortality and recurrent cardiovascular events after MI. The excess of mortality associated with Lp(a) was partially attributable to more prevalent heart failure.

Thrombin: A Pivotal Player in Hemostasis and Beyond

The serine protease thrombin, a naturally derived enzyme, plays a key role in hemostasis by converting fibrinogen to fibrin and activating coagulation factor XIII whereby the fibrin clot is stabilized. Furthermore, thrombin activates platelets through protease-activated receptors on the platelet surface. Conversely, thrombin also exerts anticoagulant effects, enhancing the protein C activity while complexed with thrombomodulin. During recent years, it has become evident that thrombin has significant effects beyond hemostasis, as it contributes also to modulation of the endothelium, promotes inflammation and angiogenesis, and plays a role in tumor progression. Yet, due to the very short half-life and almost immediate inhibition in fluid phase by antithrombin, thrombin itself remains elusive, and only indirect measurement of thrombin generation is possible. This review provides a description of structure and mechanisms of action of thrombin both in physiological and pathological processes. Furthermore, it summarizes laboratory tests that measure in vivo or ex vivo thrombin generation, and presents knowledge on the value of these biomarkers in bleeding disorders, cardiopulmonary bypass surgery, and thromboembolic risk assessment in different patient populations. Finally, this review outlines further perspectives on using thrombin generation biomarkers for research purposes and in clinical practice.

Transient ST-elevation myocardial infarction versus persistent ST-elevation myocardial infarction. An appraisal of patient characteristics and functional outcome

BACKGROUND

Up to 24% of patients presenting with ST-elevation myocardial infarction (STEMI) show resolution of ST-elevation and symptoms before revascularization. The mechanisms of spontaneous reperfusion are unclear. Given the more favorable outcome of transient STEMI, it is important to obtain further insights in differential aspects.

METHODS

We compared 251 patients who presented with transient STEMI (n = 141) or persistent STEMI (n = 110). Clinical angiographic and laboratory data were collected at admission and in subset of patients additional index hemostatic data and at steady-state follow-up. Cardiac magnetic resonance imaging (CMR) was performed at 2-8 days to assess myocardial injury.

RESULTS

Transient STEMI patients had more cardiovascular risk factors than STEMI patients, including more arterial disease and higher cholesterol values. Transient STEMI patients showed angiographically more often no intracoronary thrombus (41.1% vs. 2.7%, P < 0.001) and less often a high thrombus burden (9.2% vs. 40.0%, P < 0.001). CMR revealed microvascular obstruction less frequently (4.2% vs. 34.6%, P < 0.001) and smaller infarct size [1.4%; interquartile range (IQR), 0.0-3.7% vs. 8.8%; IQR, 3.9-17.1% of the left ventricle, P < 0.001] with a better preserved left ventricular ejection fraction (57.8 ± 6.7% vs. 52.5 ± 7.6%, P < 0.001). At steady state, fibrinolysis was higher in transient STEMI, as demonstrated with a reduced clot lysis time (89 ± 20% vs. 99 ± 25%, P = 0.03).

CONCLUSIONS

Transient STEMI is a syndrome with less angiographic thrombus burden and spontaneous infarct artery reperfusion, resulting in less myocardial injury than STEMI. The presence of a more effective fibrinolysis in transient STEMI patients may explain these differences and might provide clues for future treatment of STEMI.

Lipoprotein (a): truly a direct prothrombotic factor in cardiovascular disease?

Elevated plasma concentrations of lipoprotein (a) [Lp(a)] have been determined to be a causal risk factor for coronary heart disease, and may similarly play a role in other atherothrombotic disorders. Lp(a) consists of a lipoprotein moiety indistinguishable from LDL, as well as the plasminogen-related glycoprotein, apo(a). Therefore, the pathogenic role for Lp(a) has traditionally been considered to reflect a dual function of its similarity to LDL, causing atherosclerosis, and its similarity to plasminogen, causing thrombosis through inhibition of fibrinolysis. This postulate remains highly speculative, however, because it has been difficult to separate the prothrombotic/antifibrinolytic functions of Lp(a) from its proatherosclerotic functions. This review surveys the current landscape surrounding these issues: the biochemical basis for procoagulant and antifibrinolytic effects of Lp(a) is summarized and the evidence addressing the role of Lp(a) in both arterial and venous thrombosis is discussed. While elevated Lp(a) appears to be primarily predisposing to thrombotic events in the arterial tree, the fact that most of these are precipitated by underlying atherosclerosis continues to confound our understanding of the true pathogenic roles of Lp(a) and, therefore, the most appropriate therapeutic target through which to mitigate the harmful effects of this lipoprotein.

Relationship between lipoprotein(a) and spontaneous recanalization of infarct-related arteries in the early phase of acute myocardial infarction

BACKGROUND

Lipoprotein(a) (Lp[a]) is known to inhibit the fibrinolysis system and promote thrombus formation.

HYPOTHESIS

We retrospectively investigated the influences of Lp(a) on infarct-related artery patency in the early phase of acute myocardial infarction (AMI).

METHODS

In 144 patients with ST-segment elevation, myocardial, coronary angiography (CAG) was performed within 12 h of the onset of symptoms. Subjects were divided into 2 groups according to the thrombolysis in myocardial infarction (TIMI) grade, Group I (TIMI 0-1, n = 94) versus Group II (TIMI 2-3, n = 50). The Gensini score and 0- to 3-vessel disease score estimated the severity and extent of coronary artery disease (CAD), respectively. Lp(a), lipid profile and c-reactive protein (CRP) were measured before any medications including thrombolytics were given.

RESULTS

The Lp(a) level was higher in Group I than in Group II. There was a weak correlation between Lp(a) level and Gensini score. By multivariate logistic regression analysis, a Lp(a) level was a predictor of infarct-related artery patency in the early phase of AMI. There were no significant differences in the location of the infarct-related arteries, extent of CAD, time from pain to CAG, number of risk factors, and hs-CRP values between the 2 groups.

CONCLUSION

The Lp(a) level was significantly higher in patients with persistent occlusion compared with those with spontaneous recanalization of infarct-related arteries in the early phase of AMI.

Extracts of monascusus purpureus beyond statins —Profile of efficacy and safety of the use of extracts of monascus purpureus

Extracts of Monascus purpureus have always been considered a natural source of lovastatin, the precursor of the world's largest selling class of drugs. In actual fact, the fungus contains many other substances (flavonoids, polyunsaturated fats, pyrrolinic compounds etc.) with a wide variety of other actions. The most recent studies have shown that it has an action on the glycemic metabolism, and on the mechanisms of adipogenesis, also an effects on the endothelium and on postprandial vasodilation. These effects are more extensive and complex than those of statins alone. And new strains of Monascus purpureus have recently been patented where the presence of statins is only one of the therapeutic components of the fungus. In particular, the increase in secondary components, such as flavonoids, which coincides with a more complex therapeutic action, probably making the new extracts of Monascus purpureus, the ideal candidate for the treatment of the metabolic syndrome.

Relation between serum lipoprotein (a) and residual lesion stenosis of coronary artery after myocardial Infarction without reperfusion therapy

Lipoprotein (a) (Lp(a)) is an independent risk factor for myocardial infarction (MI). It may also inhibit the fibrinolysis system, and Lp (a) affects the natural course of MI and the results of thrombolytic therapy. The purpose of this study was to investigate the influence of Lp (a) on the residual lesion stenosis of the infarction-related arteries (residual stenosis) in acute MI patients in whom reperfusion therapy was not performed. We studied 129 MI patients not given reperfusion therapy who underwent coronary angiography in the chronic stage. Morning fasting blood was collected and Lp (a), blood sugar, total cholesterol (TC), triglycerides (TG), and hemoglobin A1c (HbA1c) were measured. Residual stenosis was compared between the low Lp(a) group (< 30 mg/dL) and the high Lp(a) group (> or = 30 mg/dL). It was severe in the high Lp(a) group (85.0 +/- 24.9% vs 94.5 +/- 15.5%, P = 0.0044). We also compared residual stenosis and TIMI classification between younger and older, non-DM and DM, non-HT and HT, low-TC (< 220 mg/dL) and high-TC (> or = 220 mg/dL), low-TG (< 150 mg/dL) and high-TG (> or = 150 mg/dL), and low-Lp (a) and high-Lp (a) patients. Only the serum Lp (a) level affected the residual stenosis and TIMI classification (P < 0.05).

CONCLUSION

These findings suggest that elevated Lp (a) levels inhibit fibrinolysis.

Effects of lipids on thrombotic mechanisms in atherosclerosis

Cholesterol lowering therapy markedly reduces the frequency of subsequent cardiovascular events and is associated with a modest degree of angiographic regression of atherosclerotic lesions. There is a strong association between lipids and fibrinogen, plasminogen activator-1, and activated factor VII levels. Low density lipoprotein may be thrombogenic whereas high density lipoprotein protects against thrombosis. Lipoprotein (a) may affect atherosclerosis and thrombosis mainly by binding to fibrin and attenuating the fibrin-enhanced plasminogen activation. Tissue factor-complex initiates coagulation by activating factor X and factor IX leading in the presence of calcium to the generation of thrombin. Lipid lowering treatment with statins stabilizes atheromatous plaque and has antithrombotic effects. Therefore there are links between lipids and the haemostatic mechanisms which affect atherosclerotic, vasomotor and thrombotic components of ischemic heart disease.

Estrogen/progesterone replacement versus pravastatin and their sequential association in hypercholesterolemic postmenopausal women

OBJECTIVES

The objectives of this study were to assess serum lipid changes in response to an oral estrogen combined with progesterone (Group A) as compared with pravastatin (Group B) and to evaluate the additive effects of the sequential addition of statin to hormonal replacement therapy (HRT) and of HRT to statin.

METHODS

Thirty-seven of 63 hypercholesterolemic menopausal women initially submitted to a 4-month diet were randomised to oral conjugated estrogens (0.625 mg)/micronised progesterone (200 mg) or to pravastatin (40 mg). After 6 months, each group received both medications for another 6 months.

RESULTS

Nineteen percent of women corrected their lipids below decision levels with diet alone. Low density lipoprotein-cholesterol (LDL-C) decreased by 8+/-5% with HRT and by 26+/-3% (P<0.001) with the statin. These single medications increased high density lipoprotein-cholesterol (HDL-C) by 13+/-5% (P<0.01) and 11+/-7%, respectively. Combined interventions produced cumulative LDL-C reductions of 40+/-2 and 42+/-3% (P<0.001) and additive HDL-C augmentations of 16+/-4 and 23+/-5% (P<0.01) with proportional changes in apolipoprotein (Apo)B-100 and ApoA-1. These combined effects brought the atherogenic index (C/HDL-C) for Groups A and B, respectively, from a moderate (5.18+/-0.25 and 5.87+/-0.18) to a reduced (3.35+/-0.20 and 3.52+/-0.19) risk category. Triglycerides (TG) which were increased by HRT and decreased by the statin returned to baseline during combined treatments. No changes in diet, physical activity or anthropomorphometric measurements explained the lipid modifications.

CONCLUSIONS

In menopausal patients with elevated C not responding to diet, pravastatin was most effective to decrease LDL-C, and oral estrogen-micronised progesterone most effective to increase HDL-C. Marked reduction of the atherogenic index is achieved by sequential combinations of medications resulting from beneficial cumulative effects on both C-LDL and C-HDL.

Relationship between serum lipoprotein(a) level and thrombin generation to the circadian variation in onset of acute myocardial infarction

A high incidence of acute myocardial infarction (AMI) has been reported between 06:00 and 12:00 h. This may be related to an abnormality in hemostasis. An association has been founded between the serum lipid level and coronary atherosclerosis, as well as the serum lipid level and a hemostatic abnormality. We investigated the association between the time of AMI, the level of serum lipid, and of hemostatic factor. Of the 42 subjects evaluated retrospectively, 20 had experienced an AMI between 06:00 and 12:00 h (group A), while 22 had developed an AMI during some other period (group B). All patients received emergency coronary angiography, which identified a total occlusion of coronary artery in the proximal portion of the left antecedent branch. The serum level of several lipid factors and of hemostatic factors were compared between the two groups. Characteristics of patients were similar in both groups. The serum levels of lipoprotein(a) (Lp(a)) and of thrombin-antithrombin III complex (TAT) were higher in group A than in group B, respectively. The level of other factors were similar in both groups. Group A showed a significant correlation between the level of Lp(a) and TAT, with a tendency (not statistically significant), toward a positive correlation between Lp(a) and PAI-1, and a negative correlation between Lp(a) and t-PA. In a subgroup that experienced AMI in the early morning, a higher level of Lp(a) was associated with an elevation of TAT, a marker for thrombin generation, and with the level of fibrinolytic factor. This suggests that Lp(a) is closely related to the increase in the early morning incidence of AMI via a change in the prothrombotic state.

Novel risk factors for atherosclerosis

In the past several years, evidence has accumulated that factors other than conventional risk factors may contribute to the development of atherosclerosis. Conventional risk factors predict less than one half of future cardiovascular events. Furthermore, conventional risk factors may not have the same causal effect in different ethnic groups in whom novel risk factors may have a role. These newer risk factors for atherosclerosis include homocysteine, fibrinogen, impaired fibrinolysis, increased platelet reactivity, hypercoagulability, lipoprotein(a), small dense low-density lipoprotein cholesterol, and inflammatory-infectious markers. Identification of other markers associated with an increased risk of atherosclerotic vascular disease may allow better insight into the pathobiology of atherosclerosis and facilitate the development of preventive and therapeutic measures. In this review, we discuss the evidence associating these factors in the pathogenesis of atherosclerosis, the mechanism of risk, and the clinical implications of this knowledge.

Importance of endothelial function in mediating the benefits of lipid-lowering therapy

Trials of lipid lowering by various methods have clearly demonstrated the benefits, clinically and angiographically. Evidence of slowed arterial disease progression and even regression has been convincing but modest, at best. For example, among those treated intensively in the Familial Atherosclerosis Treatment Study (FATS), the mean improvement in proximal stenosis severity was <1% per patient, and only 12% of all lesions showed convincing regression. Despite these modest arterial benefits, the associated reductions in major cardiovascular events have been surprisingly great (24-35% in 3 recent large trials and > or =50% in angiographic trials using combination therapies). The process of plaque disruption helps explain this discrepancy. Disruption can be predicted by a large accumulation of core lipid in the plaque and a high density of lipid-laden macrophages in its thinned fibrous cap. Lesions with these characteristics comprise only 10-20% of the overall lesion population but account for 60-90% of the acute clinical events. Lipid-lowering therapy has beneficial effects on these "high-risk" features of plaque morphology. The composite of data presented here supports the hypothesis that lipid-lowering therapy selectively depletes lipids from this relatively small but dangerous subgroup of fatty lesions, effectively stabilizing them.

Usefulness of lipids, lipoprotein(a) and fibrinogen measurements in identifying subjects at risk of occlusive complications following vascular and endovascular surgery

The study was designed to establish the usefulness of measuring lipoprotein(a) [Lp(a)], total cholesterol, triglycerides, low-density lipoprotein [LDL]-cholesterol, high-density lipoprotein [HDL]-cholesterol, total-to-HDL-cholesterol ratio and fibrinogen in identifying subjects at risk of occlusive complications following vascular and endovascular surgery, including primary successful ileofemoral percutaneous transluminal angioplasty, infrainguinal and aortic bypass graft and carotid endarterectomy. A total of 68 volunteers subjected to vascular and endovascular surgery were recruited to the study. Six months after successful interventions, no occlusive complications verified by angiography were observed in 45 patients (66%; No-restenosis group), whereas significant restenosis or reocclusion occurred in 23 patients (34%; Restenosis group). Significant lower concentrations of Lp(a) (p=0.032), total cholesterol (p<0.0001), LDL-cholesterol (p=0.001) and total-to-HDL-cholesterol ratio (p<0.0001) and higher concentrations of HDL-cholesterol (p=0.048) were observed in the No-restenosis group compared to the Restenosis group. The concentrations of triglycerides (p=0.080) and fibrinogen (p=0.510) did not differ significantly between groups. In multivariate discriminant analysis, the best predictors of restenosis or reocclusion were in decreasing order: LDL-cholesterol, Lp(a), total-to-HDL-cholesterol ratio, HDL-cholesterol and total cholesterol. A statistical difference of particular interest was observed in the overall distribution of Lp(a) concentrations between groups (p<0.0001), occlusive complications being unlikely to occur in patients with Lp(a) concentrations below 50 mg L(-1). The potential interference from a concurrent acute phase response, the most common source of elevation of Lp(a) in humans, was less likely in view of the absence of differences in erythrocyte sedimentation rate between the No-restenosis and Restenosis groups (p=0.463). In conclusion, the results of the present investigation point to a definite role of the combined measurements LDL-cholesterol, Lp(a), total-to-HDL-cholesterol ratio, HDL-cholesterol and total cholesterol in the identification of subjects at risk of occlusive events following vascular and endovascular surgical procedures.

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.