Time significance of acute thrombotic reactant markers in patients with and without silent myocardial ischemia and overt unstable angina pectoris

High-molecular-weight kininogen and the intrinsic coagulation pathway in patients with de novo acute myocardial infarction

After an acute ischaemic event serum proteins may change reflecting the ischaemic damage. Proteomic studies could provide new insights into potential biomarkers in the evolution of ischaemic syndromes. In this study we have investigated the coordinated changes in coagulation-related proteins in the evolution after an acute myocardial infarction (AMI). Serum proteome (2D-electrophoresis and MALDI-TOF/ TOF) of AMI-patients within the first 6 hours after event onset (admission-time) and 3 days after were compared to controls. Systems biology and bioinformatic analysis were performed to identify the differentially expressed canonical pathways. In silico analysis of differential proteins revealed changes in the intrinsic coagulation pathway in the early phase post-AMI. The two identified high-molecular weight kininogen (HMWK) clusters were inversely correlated in AMI patients at admission, being the intensity of the low-molecular-weight form inversely related to myocardial necrosis (p<0.05). Factor XI (FXI) levels were decreased in AMI patients at admission and normalised 3 days after (p<0.05). There was an early increase in fibrinogen gamma and D-dimer at admission, followed by a decrease in fibrinogen turnover 3 days after (p<0.05). The influence of elapsed time of ischaemia on fibrinogen distribution changes was validated in coronary thrombi retrieved by thromboaspiration. In conclusion, our results demonstrate an active exchange between HMWK forms and a decrease in FXI indicative of intrinsic pathway activation, together with an increase in fibrinogen gamma turnover and D-dimer formation in the early phase post-AMI. Moreover, coronary thrombi showed a dynamic evolution in fibrinogen composition depending on the duration of ischaemia influencing serum fibrinogen-related products content.

The role of serum D-dimer level in the diagnosis of patients admitted to the emergency department complaining of chest pain

This study investigated D-dimer levels in 241 patients admitted to the emergency department with sudden-onset chest pain. The patient group included those diagnosed with acute coronary syndrome (ACS; i.e., unstable angina pectoris [USAP], non-ST elevated myocardial infarction [NSTEMI], ST-elevated myocardial infarction [STEMI]); the control group included those diagnosed with non-cardiac chest pain. Mean serum levels of D-dimer, creatine kinase-MB (CK-MB) and troponin I (TPI) were compared between the groups. Levels of D-dimer, CK-MB and TPI in the patient group were significantly higher than in the control group. There were also significantly higher D-dimer, CK-MB and TPI levels in the STEMI and NSTEMI patient subgroups compared with the control group. Only the D-dimer level was significantly higher in the USAP subgroup versus the control group. The sensitivity and specificity of D-dimer for ACS were 83.7% and 95.4%, respectively, suggesting that evaluating D-dimer levels might be useful in the emergency room for diagnosing ACS and predicting mortality in patients presenting with acute chest pain.

Protective effect of L-arginine in experimentally induced myocardial ischemia: comparison with aspirin

OBJECTIVE

Coronary artery diseases including myocardial ischemia (MI) remain one of the leading causes of death worldwide. This study was designed to compare the protective effect of L-arginine versus aspirin from the biochemical changes associated with MI injury.

EXPERIMENTAL DESIGN

Four groups of male New Zealand white rabbits were investigated. Normal group (n = 8) rabbits were fed standard chow pellets, untreated MI group (n = 16), where hypercholesterolemia was induced by feeding the animals with a diet containing 2% cholesterol for 28 days, L-arginine group (n = 12) rabbits were fed a 2% cholesterol-enriched diet in conjunction with L-arginine (2.25 g %) in drinking water for 28 days, and aspirin group (n = 12) rabbits were fed 2% cholesterol-enriched diet in conjunction with aspirin administered orally (0.7 mg/kg per d) for 28 days. After 28 days, MI was induced in all groups, except the normal group, by a single subcutaneous (sc) injection of isoproterenol hydrochloride (0.2 mg/kg body weight [bw]). Animals were sacrificed 6 hours later.

RESULTS

Our results showed that L-arginine was more effective than aspirin in reducing platelet aggregation, reducing low-density lipoprotein (LDL) oxidizability, preventing aortic intimal thickening, and maintaining histological architecture of the myocardium. Both drugs, however, had similar positive effects on plasma fibrinogen levels and on the prevention of myocardial release of cardiac troponin I and creatine kinase-MB. The effect on hypercholesterolemia was insignificant for both drugs. Aspirin was more effective than L-arginine in prolonging prothrombin time.

CONCLUSION

L-arginine supplementation represents a potentially novel nutritional strategy for preventing and treating coronary artery diseases especially in cases of aspirin resistance and/or hypersensitivity.

[Secondary prevention of coronary artery disease. Flu vaccinations and new evidence of the role of infection in acute coronary syndromes]

Recent reports have detected an increase in the number of patients with acute coronary syndromes during the flu season. More recently, case-control studies of patients with prior infarction have shown that flu vaccination significantly reduces the risk of myocardial necrosis and strokes. The World Health Organization recommended flu vaccination for the Southern Hemisphere in the winter of 2001. We evaluated the preventive impact of flu vaccination on subsequent ischemic events in myocardial infarction patients and in subjects undergoing scheduled percutaneous coronary angioplasty. In the first study we included 200 myocardial infarction patients admitted in the first 72 hours and 100 patients scheduled for angioplasty/stent (PCI) without unstable coronary artery disease, prior bypass surgery, angioplasty or tissue necrosis, were included in a prospective, multicenter registry, during the winter season. Infarction patients received standard therapy, and then were randomly allocated in a single-blind manner as a unique intramuscular Influenza vaccination or as controls. Similarly, PCI patients were allocated to either vaccination or control. The first primary outcome -cardiovascular death- occurred within 6 months in 2% of the patients in the vaccinnated group vs 8% of controls (RR: 0.25; 95% CI, 0.07-0.86; p = 0.01). The triple composite end point occurred in 11% of the patients in the vaccinnated group vs 23% of controls (p = 0.009) at 6 months. Although our study is the first to demonstrate lower rates of cardiovascular ischemic events in patients vaccinated against Influenza during the flu season, the modification of flu vaccination recommendations in patients admitted for cardiovascular events merits further study before being considered.

Occlusive vascular diseases in oral contraceptive users. Epidemiology, pathology and mechanisms

Despite being an unprecedented departure from normal physiology, the combined oral contraceptive is not only highly effective, but it also has a remarkably good safety record. Concerns over safety persist, though, particularly with regard to venous thromboembolism (VTE), stroke and myocardial infarction (MI). Epidemiological studies consistently show an increase in risk of VTE, but the results are more contentious with regard to arterial diseases. Despite 40 years of research, the mechanisms behind these adverse effects are not understood. In this review, we integrate information from published studies of the epidemiology and pathology of the occlusive vascular diseases and their risk factors to identify likely explanations for pathogenesis in oral contraceptive users. Oral contraceptives induce both prothrombotic and fibrinolytic changes in haemostatic factors and an imbalance in haemostasis is likely to be important in oral contraceptive-induced VTE. The complexity of the changes involved and the difficulty of ascribing clinical significance has meant that uncertainty persists. A seriously under-researched area concerns vascular changes in oral contraceptive users. Histologically, endothelial and intimal proliferation have been identified in women exposed to high plasma estrogen concentrations and these lesions are associated with thrombotic occlusion. Other structural changes may result in increased vascular permeability, loss of vascular tone and venous stasis. With regard to arterial disease risk, epidemiological information relating to dose effects and joint effects with other risk factors, and studies of pathology and changes in risk factors, suggests that oral contraceptive use per se does not cause arterial disease. It can, nevertheless, synergise very powerfully with subclinical endothelial damage to promote arterial occlusion. Accordingly, the prothrombotic effects of the oral contraceptive estrogen intervene in a cycle of endothelial damage and repair which would otherwise remain clinically silent or would ultimately progress - in, for example, the presence of cigarette smoking or hypertension - to atherosclerosis. Future work in this area should focus on modification of the effects of established risk factors by oral contraceptive use rather than modification of the supposed risk of oral contraceptive use by established risk factors. Attempts to understand vascular occlusion in oral contraceptive users in terms of the general features of VTE or with reference to atherosclerosis may be limiting, and future work needs to acknowledge that such occlusions may have unique features. Unequivocal identification of the mechanisms involved would contribute considerably to the alleviation of fears over vascular disease and to the development of even safer formulations.

D-Dimer is an early diagnostic marker of coronary ischemia in patients with chest pain

BACKGROUND

Chest pain is a frequent symptom in the emergency department and often presents a diagnostic challenge. Because coronary thrombosis is a hallmark of acute ischemic syndromes, the substrates of the coagulation and fibrinolysis cascades may be markers of coronary ischemia. The objective of this study was to determine the diagnostic value of several hemostatic markers in patients presenting to the emergency department (ED) with chest pain syndromes.

METHODS

Two hundred fifty-seven consecutive patients with acute chest pain were studied in this prospective study conducted in an urban ED. D-Dimer levels were measured at admission to the ED in all patients. We also measured thrombin-antithrombin complexes, prothrombin fragment 1+2, activated factor VII, and fibrinogen. We used regression analysis to estimate the likelihood of myocardial infarction and the diagnostic value of D-dimer.

RESULTS

D-Dimer and fibrinogen levels were significantly higher in patients with acute ischemic events (myocardial infarction and unstable angina) than in nonischemic patients (P <.01 and P =.02, respectively). The other hemostatic markers were not significantly elevated in patients with ischemic events. D-Dimer level >500 microg/L had an independent diagnostic value for myocardial infarction and increased the diagnostic sensitivity of the electrocardiogram and history from 73% to 92%.

CONCLUSION

D-Dimer, an expression of ongoing thrombus formation and lysis, is a marker of substantial incremental value for the early diagnosis of acute coronary syndromes presenting with chest pain. It adds independent information to the traditional assessment for myocardial infarction. D-Dimer can be incorporated into clinical decision models in the ED.

Chlamydia pneumoniae: inflammation and instability of the atherosclerotic plaque

Coronary heart disease remains the most common cause of death in industrialized countries. Although atherosclerosis is generally asymptomatic in the early stages, progressive plaque development leads to arterial stenosis which is characterized by angina and may eventually lead to unstable angina, myocardial infarction and cardiac death. Evidence that the coagulation cascade is activated during acute coronary events has justified the use of antithrombotic agents such as aspirin, heparin and low molecular weight heparin (LMWH) in the standard management of acute coronary syndromes. The inflammatory process is also known to play a significant role in the pathogenesis of atherosclerosis, resulting in a cycle of continued inflammatory cell activation and ongoing cell recruitment. As the human leukocyte-associated antigen (HLA) system plays a key role in the regulation of the inflammatory process, the expression of HLA antigens in patients with symptomatic coronary heart disease has been investigated. These studies have demonstrated a relationship between the major histocompatibility complex (MHC) class II expression and the most severe pattern of angina refractory to conventional therapy, within the framework of a chronic infectious disease. A number of studies have documented an association between coronary heart disease and the presence of high titres of antibodies to Chlamydia pneumoniae, and this organism has been implicated in plaque instability. Such findings have stimulated interest in the role of C. pneumoniae in the pathogenesis of coronary heart disease, with a view to developing novel and effective treatment approaches. The ROXIS study showed a lower incidence of acute ischaemic events in patients with unstable angina treated with an antichlamydial antibiotic, roxithromycin.

Rationale for the management of coronary syndromes with low-molecular-weight heparins

The well-documented disadvantages of unfractionated heparin in the management of coronary syndromes, such as unpredictable bioavailability and maintenance of therapeutic range, has prompted several studies into the benefits of low-molecular-weight heparins (LMWHs). The favorable pharmacologic properties of LMWHs include a binding affinity for antithrombin III, anti-factor IIa activity, excellent bioavailability, minimal protein binding, predictable anticoagulant response, and clinical tolerance by patients. LMWHs are also characterized by having a specific anti-factor Xa effect and inducing only a small prolongation in general clotting tests-i.e., activated partial thromboplastin time, prothrombin time, and antithrombin activity-when used in high doses. Several studies have recently demonstrated that LMWHs are superior to placebo and are at least equal or superior to standard heparin when added to aspirin for the treatment of unstable angina and following non-Q-wave myocardial infarction. These studies, which include Thrombolysis in Myocardial Infarction (TIMI) 11A and Efficacy and Safety of Subcutaneous Enoxaparin versus intravenous unfractionated heparin in Non-Q-wave Coronary Events (ESSENCE), will be reviewed and discussed.

Evaluation of chest pain in the emergency department

The evaluation of chest pain in the emergency setting should be systematic, risk based, and goal driven. An effective program must be able to evaluate all patients with equal thoroughness under the assumption that any patient with chest pain could potentially be having an MI. The initial evaluation is based on the history, a focused physical examination, and the ECG. This information is sufficient to categorize patients into groups at high, moderate, and low risk. Table 14 is a template for a comprehensive chest-pain evaluation program. Patients at high risk need rapid initiation of appropriate therapy: thrombolytics or primary angioplasty for the patients with MIs or aspirin/heparin for the patients with unstable angina. Patients at moderate risk need to have an acute coronary syndrome ruled in or out expediently and additional comorbidities addressed before discharge. Patients at low risk also need to be evaluated, and once the likelihood of an unstable acute coronary syndrome is eliminated, they can be discharged with further evaluation performed as outpatients. Subsequent evaluation should attempt to assign a definitive diagnosis while also addressing issues specific to risk reduction, such as cholesterol lowering and smoking cessation. It is well documented that 4% to 5% of patients with MIs are inadvertently missed during the initial evaluation. This number is surprisingly consistent among many studies using various protocols and suggests that an initial evaluation limited to the history, physical examination, and ECG will fail to identify the small number of these patients who otherwise appear at low risk. The solution is to improve the sensitivity of the evaluation process to identify these patients. It appears that more than simple observation is required, and at the present time, no simple laboratory test can meet this need. However, success has been reported with a number of strategies including emergency imaging with either radionuclides such as sestamibi or echocardiography. Early provocative testing, either stress or pharmaceutic, may also be effective. The added value of these tests is only in their use as part of a systematic protocol for the evaluation of all patients with acute chest pain. The initial evaluation of the patient with chest pain should always consider cardiac ischemia as the cause, even in those with more atypical symptoms in whom a cardiac origin is considered less likely. The explicit goals for the evaluation of acute chest pain should be to reduce the time to treat MIs and to reduce the inadvertent discharge of patients with occult acute coronary syndromes. All physicians should become familiar with appropriate risk stratification of patients with acute chest pain. Systematic strategies must be in place to assure rapid and consistent identification of all patients and the expedient initiation of treatment for those patients with acute coronary syndromes. These strategies should include additional methods of identifying acute coronary syndromes in patients initially appearing as at moderate or low risk to assure that no unstable patients are discharged. All patients should be followed up closely until the cardiovascular evaluation is completed and, when possible, a definitive diagnosis is determined. Finally, this must be done efficiently, cost-effectively, and in a manner that will result in an overall improvement in patient care.