Aspirin in the prevention of coronary disease

Improvement of cardiovascular risk prediction using coronary imaging: subclinical atherosclerosis: the memory of lifetime risk factor exposure

Deaths from diseases of the heart are decreasing. Cardiovascular diseases (CVD) will be the main cause of morbidity and mortality in 2015 according to a WHO report. The main problem is related to the long-time delay between the start of the development of atherosclerosis in young adults and the manifestation many decades later. Despite a recent decline in a CVD mortality rate in men and women, the main problem is related to the acute manifestation as the acute coronary syndrome, which leads 30-50% of subjects to sudden and fatal outcomes. In addition, about 20% of first and recurrent acute myocardial infarctions are silent. The lifetime risk of coronary artery disease after 40 years is 49% for men and 32% for women. That means, we are confronted with a major health care problem. This is even more obvious, when the rate of coronary heart disease deaths out of the hospital are taken into account which amount to 70% in 2007. These data are confirmed for Europe despite a strong decline of hospital deaths. Another problem is related to the fact that the number of sudden cardiac death amounts to >300 000 in the general US population. It is about 10 times higher than in those patients who are defined as prone to sudden death due to low ejection fraction, ventricular arrhythmias, and acute myocardial infarction. For cardiologists, this general topic becomes even more obvious, because even well-known cardiologists experienced early (≤65 years) sudden cardiac deaths such as RW Campbell, JM Isner, PA Poole-Wilson, H Drexler, and recently the paediatric cardiologist from Hannover, A Wessels. These events underline again what has been emphasized 15 years ago by the MONICA study that two-thirds of patients die outside the hospital and that we have to concentrate on primary and secondary prevention, also in memory of these colleagues. This review will demonstrate the potential value of coronary artery calcification screening which can be used as a sign of subclinical coronary arteriosclerosis for improved risk prediction, the first step to prevention. Subclinical atherosclerosis represents the vessel memory of risk factor exposure.

Low-dose aspirin in the primary prevention of rheumatoid arthritis: the Women's Health Study

OBJECTIVE

Low-dose aspirin may reduce the risk of developing rheumatoid arthritis (RA) through its effect on cyclooxygenase activity and its antioxidant pathways. Previous randomized trial data have demonstrated a beneficial effect of low-dose aspirin in reducing other inflammatory diseases, such as asthma and colorectal adenomas, but no trial has evaluated the role of aspirin in RA prevention.

METHODS

The Women's Health Study is a randomized, double-blind, placebo-controlled trial conducted between 1992 and 2004 designed to evaluate the risks and benefits of low-dose aspirin (100 mg every other day) and vitamin E in the primary prevention of cardiovascular disease and cancer among 39,876 female health care professionals age > or =45 years throughout the US. After excluding women with RA at baseline, 39,144 women were evaluated for the present study. A definite diagnosis of RA was assessed during followup by self-report and confirmed using a connective tissue disease screening questionnaire, followed by a medical record review by a rheumatologist for American College of Rheumatology criteria.

RESULTS

During an average followup of 10 years, 106 women developed definite RA (48 women in the aspirin group and 58 in the placebo group). There was a nonsignificant risk for RA (relative risk [RR] 0.83, 95% confidence interval [95% CI] 0.56-1.21; P = 0.33) associated with aspirin. There were 64 seropositive RA cases (60%) and 42 seronegative RA cases (40%). Aspirin also had no significant effect on either seropositive RA (RR 1.0, 95% CI 0.61-1.63) or seronegative RA (RR 0.62, 95% CI 0.33-1.15).

CONCLUSION

One hundred milligrams of aspirin taken every other day was not associated with a significant reduction in the risk of developing RA among women in a randomized, double-blind, placebo-controlled trial.

Aspirin decreases vascular endothelial growth factor release during myocardial ischemia

BACKGROUND

Vascular Endothelial Growth Factor (VEGF) is an important angiogenesis factor involved in pathophysiology of cardiovascular diseases. Controlling this factor's level in the serum might have significant prognostic outcomes.

METHODS

Twenty-four patients undergoing coronary artery bypass grafting were prospectively categorized into two groups according to aspirin administration before surgery. Vascular Endothelial Growth Factor levels were compared and correlated and adjusted with platelets count between two groups in the serum, before and after the surgery. Serum creatine kinase (CK) levels were determined before and after the operation in parallel to other clinical data.

RESULTS

Vascular Endothelial Growth Factor levels were significantly lower in patients of the aspirin group compared to those of the non-aspirin group; 94+/-61 vs. 241+/-118 pg/ml, p=0.0003, respectively, this-despite an absence of difference in the platelet count between the groups. These titers decreased postoperatively in both groups, 94+/-61 to 10+/-9 pg/ml, p=0.001 in aspirin group and from 241+/-118 to 84+/-54 pg/ml, p=0.001 in control group. Serum creatine kinase levels were higher in the non-aspirin group, 214+/-83 u/l compared to 70+/-32 u/l in the aspirin group. Creatine kinase levels increased significantly postoperatively in both groups; however, the aspirin group had a significantly lower creatine kinase levels compared to non-aspirin group, 107+/-51 vs. 401+/-127 u/l, respectively, p=<0.0001. A significant correlation was seen between VEGF levels and platelets count in both groups, r=0.5.

CONCLUSIONS

Aspirin treated patients have lower Vascular Endothelial Growth Factor titer levels in the perioperative course. This difference between the aspirin and the non-aspirin group is not accounted for by the platelets count.

Effect of preoperative aspirin use in off-pump coronary artery bypass operations

BACKGROUND

The effect of preoperative aspirin use until the day of operation on mortality rate and bleeding risks in patients who had on-pump coronary artery bypass operation has been well documented. However, the effect of aspirin use in patients undergoing off-pump coronary artery bypass operation (OPCAB) with regard to postoperative blood loss and morbidity has not been studied. We aimed to determine the effects of continuing aspirin therapy preoperatively.

METHODS

We performed a retrospective study of 340 patients who had first-time OPCAB between January 1998 and September 2001. A propensity score for receiving aspirin until the day of operation was constructed from core patient characteristics. All aspirin users (n = 170) were matched with unique 170 nonaspirin users by identical propensity score. The primary outcome measures were in-hospital mortality rate and hemorrhage-related outcomes (postoperative blood loss in the intensive care unit, reexploration for bleeding, and blood product requirements). Secondary outcome measures were stroke, myocardial infarction, gastrointestinal bleeding, and sternal wound infections.

RESULTS

There were no differences in patient characteristics between aspirin users and nonaspirin users. The average postoperative blood loss (845 mL versus 775 mL; p = 0.157) and the rate of reexploration for bleeding (3.5% versus 3.5%; p > 0.99) were similar in aspirin users and nonaspirin users. We found no significant difference between blood product requirements for the two groups. Similarly, we found no significant difference in the incidence of the secondary outcomes.

CONCLUSIONS

Preoperative aspirin did not increase bleeding-related complications, mortality rate, or other morbidities in patients who had off-pump coronary artery operation.

Effect of preoperative aspirin use on mortality in coronary artery bypass grafting patients

BACKGROUND

Discontinuing aspirin use in patients before coronary artery bypass grafting (CABG) has focused on bleeding risks. The effect of aspirin use on overall mortality with this procedure has not been studied.

METHODS

We performed a case patient-control patient study of the 8,641 consecutive isolated CABG procedures performed between July 1987 and May 1991 in Maine, New Hampshire, and Vermont. Patients included all 368 deaths. Each case patient was paired with approximately two matched survivors (control patients). Aspirin use was defined by identification of ingestion within 7 days before the operation.

RESULTS

CABG patients using preoperative aspirin were less likely to experience in-hospital mortality in univariate (odds ratio [OR] = 0.73, 95% confidence interval [0.54, 0.97]) and multivariate [OR = 0.55, (0.31, 0.98)] analysis compared to nonusers. No significant difference was seen in the amount of chest tube drainage, transfusion of blood products, or need for reexploration for hemorrhage between patients who did and did not receive aspirin.

CONCLUSIONS

Preoperative aspirin use appears to be associated with a decreased risk of mortality in CABG patients without significant increase in hemorrhage, blood product requirements, or related morbidities.

Glycoprotein IIIa Pl(A1/A2) polymorphism and sudden cardiac death

OBJECTIVES

We studied the association of the Pl(A1/A2) polymorphism with coronary thrombosis, myocardial infarction (MI) and sudden cardiac death (SCD) in autopsied victims of sudden death.

BACKGROUND

Sudden cardiac death is one of the leading symptoms of coronary heart disease in early middle age. Platelet glycoprotein (GP)IIb/IIIa fibrinogen receptors play a key role in coronary thrombosis and MI. Pl(A1/A2) polymorphism of the gene for GPIIIa has been previously studied in hospital MI patients. Significance of the Pl(A1/A2) polymorphism in victims of SCD is not known.

METHODS

The Pl(A1/A2) polymorphism was studied in the Helsinki Sudden Death Study comprising 700 autopsied middle-aged white Finnish men (33 to 70 years, mean 53 years) who suffered sudden or violent out-of-hospital death.

RESULTS

Prevalence of the A2 allele decreased with age in the series. This decrease was observed among victims of SCD (n = 281) but not in men who died violently (n = 258) or of other diseases (n = 127). Of SCD victims below 50 years, 39.7% were carriers of the A2 allele compared with 28.3% among men under 50 who died of other causes (odds ratio [OR] 2.5, p = 0.01). Men with acute fatal coronary thrombosis (n = 39) were more often (OR 3.4, p < 0.01) carriers of the A2 allele than were men (n = 242) with SCD in the absence of acute coronary thrombosis (48.7% vs. 24.4%, respectively). In addition, men with MI and recent or old thrombosis (n = 67) were more often (OR 3.6, p = 0.005) carriers of the A2 allele than were men (n = 123) with MI in the absence of thrombosis (44.8% vs. 20.3%, respectively). These associations were especially strong in men under 60.

CONCLUSIONS

Our results suggest that the A2 allele of the Pl(A1/A2) polymorphism of GPIIIa is a major risk factor of coronary thrombosis and may be one important predictor of SCD in early middle age.

The French paradox and wine drinking

Despite a high level of risk factors such as cholesterol, diabetes, hypertension and a high intake of saturated fat, French males display the lowest mortality rate from ischaemic heart disease and cardiovascular diseases in Western industrialized nations (36% lower than the USA and 39% lower than the UK). By contrast, mortality from all causes is only 8% lower than in the USA and 6% than in the UK, owing to a high level of cancer and violent deaths. In a recent study of 34,000 middle-aged men from Eastern France with a follow-up of 12 years we have observed that for 48 g of alcohol (mostly wine) per day as the mean intake, mortality from cardiovascular diseases was lower by 30%, all-cause mortality was reduced by 20%, but mortality by cancer and violent death was increased compared with abstainers. Thus the so-called 'French Paradox' (a low mortality rate specifically from cardiovascular diseases) may be due mainly to the regular consumption of wine.

Dietary management of cardiovascular diseases

Since cholesterol was discovered in atherosclerotic plaques and was able, when given in diet, to induce the same type of lesions in animals, the aim of previous dietary changes was to reduce serum cholesterol as much as possible. For this purpose, the intake of saturated fats was decreased and replaced by linoleic acid, the main fatty acid lowering cholesterol. Nevertheless, this type of diet in primary or secondary prevention did not succeed in reducing satisfactorily cardiovascular and total mortality unless the intake of fish (DART and Hjermann trials) i.e. of n-3 fatty acids, was increased. On the other hand, the diet with the greatest life expectancy in the western world is that of Crete, largely vegetarian with a high intake of alpha-linolenic acid. Such a diet, compared to the usual prudent diet in 600 patients after a first myocardial infarction, reduced within a few months all cause mortality and cardiovascular events by more than 70%. Thus a highly palatable diet adapted from Crete seems to be much more efficient to prevent recurrences and death after a first myocardial infarction than the hypocholesterolemic diet presently advised.

Effects of alcohol on platelet functions

Recent epidemiologic studies have consistently shown that moderate intake of alcoholic beverages protect against morbidity and mortality from coronary heart disease and ischemic stroke. By contrast, alcohol drinking may also predispose to cerebral hemorrhage. These observations suggest an effect of alcohol similar to that of aspirin. Several studies in humans and animals have shown that the immediate effect of alcohol, either added in vitro to platelets or 10 to 20 min after ingestion, is to decrease platelet aggregation in response to most agonists (thrombin, ADP, epinephrine, collagen). Several hours later, as, in free-living populations deprived of drinking since the previous day it is mostly secondary aggregation to ADP and epinephrine and aggregation to collagen that are still inhibited in alcohol drinkers. By contrast, in binge drinkers or in alcoholics after alcohol withdrawal, response to aggregation, especially that induced by thrombin, is markedly increased. This rebound phenomenon, easily reproduced in rats, may explain ischemic strokes or sudden death known to occur after episodes of drunkenness. The platelet rebound effect of alcohol drinking was not observed with moderate red wine consumption in man. The protection afforded by wine has been recently duplicated in rats by grape tannins added to alcohol. This protection was associated with a decrease in the level of conjugated dienes, the first step in lipid peroxidation. In other words, wine drinking does not seem to be associated with the increased peroxidation usually observed with spirit drinking. Although further studies are required, the platelet rebound effect of alcohol drinking could be associated with an excess of lipid peroxides known to increase platelet reactivity, especially to thrombin.

Investigation of the influence of acetylsalicylic acid on the steady state of long-term therapy with theophylline in elderly male patients with normal renal function

The risk inherent in the clinical control of patients with theophylline is widely recognized. Elderly patients may present an additional risk because of altered pharmacokinetics and the use of concomitant medication. Acetylsalicylic acid has been proposed for primary and secondary prevention of myocardial infarction and possible strokes. This investigation was undertaken to determine if concomitant administration of acetylsalicylic acid in elderly patients would alter steady-state levels of theophylline. A population of smoking male patients older than 60 years of age under long-term control of chronic obstructive pulmonary disease (COPD) with theophylline were evaluated for a baseline period of 3 days. Serum levels were measured at 6:00 AM and 6:00 PM. An enteric-coated acetylsalicylic acid preparation, 650 mg by mouth, was added to the daily slow-release theophylline, 6:00 AM hour dose regimen for 4 weeks. The serum levels of theophylline and salicylates were measured at 6:00 PM after dosing and at 6:00 AM the following day, at weekly intervals for 4 weeks. Urine specimens collected before administration of medication at 6:00 AM were analyzed for salicylates to further confirm dosage compliance. All volunteers continued to be clinically controlled throughout the treatment period and no symptoms of either overdose or underdose of either medication occurred. Plateau or trough theophylline serum levels did not change significantly during the salicylate treatment period. Salicylate serum levels did show during treatment self-induced metabolism. It is concluded that in elderly male patients, a daily concomitant therapeutic salicylate regimen does not alter steady-state serum theophylline levels and therefore does not per se necessitate the assay of theophylline blood levels in elderly patients.

Alleviation of experimental cyclosporin A nephrotoxicity by low dose aspirin in the rat

Groups of male Sprague-Dawley rats received either cyclosporin A (CsA; 25 mg/kg by gavage), low dose aspirin (ASP; 20 mg/kg by gavage), a combination of both, or the appropriate drug vehicles daily for 14 days. Renal structure and function were assessed on day 0 (pretreatment) and on days 7 and 14. Compared to pretreatment results, CsA nephrotoxicity was characterized by increased plasma urea and creatinine concentrations and by moderate to severe microcalcification (MC) at the corticomedullary junction by day 14. The development of nephrotoxicity was also associated with a 5-fold increase in urine thromboxane B2 (TxB2) excretion by day 10, while that of 6-ketoprostaglandin F1 alpha remained relatively constant. Although both ASP and saline (ASP vehicle) -cotreated animals demonstrated significantly lower plasma urea and creatinine concentrations compared to treatment with CsA alone, the severity of MC observed on day 14, was reduced only in the ASP cotreatment group. Though whole blood CsA concentrations were similar at around 2400 ng/mL in all experimental groups. In addition, although a 2-fold increase in urine TxB2 excretion was observed on days 7 and 10 following treatment with CsA/ASP, levels were significantly reduced compared to treatment with either CsA alone or CsA/saline (both P < 0.05).

Acute myocardial infarction in the diabetic patient: pathophysiology, clinical course and prognosis

Although there have been significant advances in the care of many of the extrapancreatic manifestations of diabetes, acute myocardial infarction continues to be a major cause of morbidity and mortality in diabetic patients. Factors unique to diabetes increase atherosclerotic plaque formation and thrombosis, thereby contributing to myocardial infarction. Autonomic neuropathy may predispose to infarction and result in atypical presenting symptoms in the diabetic patient, making diagnosis difficult and delaying treatment. The clinical course of myocardial infarction is frequently complicated and carries a higher mortality rate in the diabetic than in the nondiabetic patient. Although the course and pathophysiology of myocardial infarction differ to some degree in diabetic patients from those in patients without diabetes, much more remains to be known to formulate more effective treatment strategies in this high risk subgroup.

[Incidence of use of various myocardial infarct treatments in 2 Swiss regions]

Two regions in Switzerland (Vaud-Fribourg and Ticino) participate in the WHO MONICA project (MONItoring of trends and determinants in CArdiovascular disease). Within this context, all hospitalizations of men for ischemic heart disease will be recorded during a period of ten years. All cases are classified according to uniform criteria, in three categories: definite myocardial infarction, possible myocardial infarction or no myocardial infarction. In 1986, the records were completed with a summary of treatments. The treatment of 334 patients with definite myocardial infarction, aged between 25 and 64 years, surviving after 27 days are analyzed (VD-FR: 217; TI: 117). Results show that anticoagulants were administered in a routine fashion (in 97% of the cases), whilst thrombolysis, applied in 1986 by only one hospital in each area, concerned only 9% of the patients. As compared to Ticino, VD-FR distinguished itself by its significantly higher use of anti-arrhythmia drugs (69% versus 47%; p less than 0.005), nitrates (97% versus 86%; p less than 0.005) and beta-blockers (57% versus 43%; p less than 0.05). Furthermore, patients from VD-FR spent more time in the intensive care unit (6.4 versus 3.7 days; p less than 0.005) and participated more frequently in rehabilitation programmes (47% versus 12%; p less than 0.005). The discussion compares the observed therapy with results published in the literature.

The porcine model for the understanding of thrombogenesis and atherogenesis

The hypothesis originated by Carl Rokitansky a century ago that thrombosis contributes substantially to atherosclerosis has been rekindled by accumulating experimental and clinical evidence. On the basis of our experience with the experimental porcine model, several important biologic determinants of thrombosis have been identified. The degree of vascular injury seems to be the primary determinant of the thrombotic response. In addition, hemodynamic shear stress and the presence of the von Willebrand factor have important roles in the process of thrombosis. Although there is little evidence that thrombosis is a factor in the initiation of spontaneous, or naturally occurring, atherosclerosis, substantial evidence suggests that thrombosis has an essential role in the progression of spontaneous atherosclerosis and also in the early pathogenic process of the syndromes of accelerated atherosclerosis-namely, heart transplant atherosclerosis, vein graft disease, and coronary restenosis after angioplasty. Advances in the understanding of vascular injury and of the interactions of blood cells with the vascular wall have allowed development of new experimental antithrombotic strategies and subsequent clinical applications in the prevention of these vascular diseases.

Platelet fatty acids and function in two distinct regions of Belgium: relationship to age and dietary habits

We compared the dietary habits, fatty acid composition of plasma and platelet phospholipids, and platelet function in two groups of healthy Belgian male subjects, known to differ in their mortality rate from coronary heart disease (CHD). In the Walloon subjects, there was a larger intake of saturated and a lower intake of (n-6) polyunsaturated fats, confirmed by the fatty acid composition of plasma and platelet phospholipids. While plasma HDL and total cholesterol were similar in the present samples of the two communities, platelet aggregation to epinephrine was significantly higher in the Walloon subjects. When the two populations were divided into younger (28-54 years) and older (55-73 years) age groups, the older Walloon subjects exhibited platelet hyper-aggregability to most of the agonists, compared to the other three groups. In addition to dietary fats, alcohol and smoking habits, age was an important determinant of platelet phospholipid fatty acids and platelet reactivity. The present results reinforce those of previous studies, indicating that platelet behaviour is significantly affected by the main risk factors for CHD.

Oxidative status and oral contraceptive. Its relevance to platelet abnormalities and cardiovascular risk

Oral contraceptive (OC) use is a risk for thrombogenic events. This paper reviews effects of OC on oxidative status, coagulation, and platelet activity. Complicating effects of cardiovascular risk factors such as smoking, diabetes, hyperpidemia, and hypertension, are discussed. From these data we conclude that: 1. OC use modifies slightly but significantly the oxidative status in women and in animals by decreasing in plasma and blood cells the antioxidant defenses (vitamins and enzymes). 2. The changes in the oxidative status are related to an increase in plasma lipid peroxides apparently responsible for the hyperaggregability and possibly the imbalance in clotting factors associated with the OC-induced prethrombotic state. 3. These effects of OC appear to be increased by a high intake of polyunsaturated fat and counteracted by supplements of vitamin E. 4. The risk factors acting synergistically with OC, have all been shown to increase platelet reactivity. In addition, smoking, diabetes, and, to some extent, dyslipidemia are associated with an increased level of lipid peroxides and concomitant changes in the antioxidant defenses that can be additive to those induced by OC. Thus, free radicals and lipid peroxidation could be the underlying mechanism in the predisposition to thrombosis induced by most risk factors in OC users. 5. Results of epidemiologic and experimental studies in this field will be concordant only when diet and natural antioxidants will be systematically taken into consideration.

Platelet thromboxane A2/prostaglandin H2 receptors in human volunteers on low doses of aspirin

Administration of aspirin (81 mg/day for 2-3 weeks) in nine healthy volunteers (out of an initial ten subjects, only nine qualified) resulted in a greater than 95% decrease of thromboxane B2 production by thrombin-stimulated platelets. At the same time, ligand binding studies with a thromboxane A2 antagonist, 125I-PTA-OH, measurements of shape change, and aggregation of platelets stimulated with U46619, a prostaglandin H2 analogue, indicated that administration of aspirin to normal human subjects does not result in the up-regulation of platelet thromboxane A2/prostaglandin H2 receptors.

Pathogenesis of atherosclerosis: state of the art

The practical implementation of the results of large, well-controlled clinical and epidemiologic studies has led to substantial progress in the prevention of atherosclerosis. Now, daring and aggressive interventions, as well as a new understanding of cellular and molecular mechanisms of atherogenesis, also provide new possibilities of effective treatments at an advanced, symptomatic stage of the disease. An abundance of new information has come from an increasing number of seemingly unrelated scientific fields, ranging from laser optics to genetic engineering. This short study examines how some selected new findings and concepts fit into the traditional theories of atherogenesis: encrustation, infiltration, and response to injury. Endothelial and smooth muscle cells, platelets, and leukocytes are viewed in their dual capability of promoting as well as inhibiting the atherogenic process. Mechanisms of vascular healing and intimal hyperplasia after physical interventions are distinguished from those leading to complicated spontaneous atherosclerotic plaques, and the impact of some new ideas on potential pharmacologic interventions is brought to the reader's attention.

Role of platelet inhibitor therapy in myocardial infarction

Atherosclerotic plaque disruption is the predominant pathogenetic mechanism underlying the acute coronary syndromes. Plaque rupture leads to the exposure of collagen and vessel media, resulting in platelet and clotting activation, and occlusive thrombus formation. While drugs that interfere with platelet activation and function have been available for years, more powerful agents with novel mechanisms of action are being developed. Of the available platelet inhibitor drugs, only aspirin, sulfinpyrazone, and dipyridamole have undergone extensive clinical testing in patients with cardiovascular disease. More recently ticlopidine, a new and potent platelet inhibitor, has been successfully tested in patients with coronary and vascular disease. In acute myocardial infarction, aspirin significantly reduces cardiovascular mortality and reinfarction. Furthermore, the combination of aspirin and a thrombolytic agent produces maximal benefit. A role for heparin in the prevention of early mortality and reinfarction is emerging. This drug is effective for the prevention of left ventricular thrombosis in patients with anterior myocardial infarction. In the secondary prevention of reinfarction and cardiovascular mortality, available data support the use of a platelet inhibitor. Trials have shown that aspirin is as effective alone as in combination with dipyridamole, and is probably more effective than sulfinpyrazone. Long-term anticoagulant therapy also appears to be beneficial, but is associated with a high cost, need for extensive monitoring, and potential for hemorrhagic side effects. The role of aspirin in primary prevention is controversial. It may be indicated for patients at high risk for coronary disease in whom the benefit of therapy may outweigh the potential risk of cerebral bleeding. Coronary atherosclerotic plaque rupture, associated with thrombus formation, is fundamental to the development of acute myocardial infarction. Based on this concept, the role of antithrombotic therapy for the prevention or treatment of ischemic events in patients with coronary artery disease has stimulated enormous interest among clinicians and basic investigators. In this review we will examine: a) the pathogenesis of coronary thrombosis, b) the pharmacology of platelet-inhibitor agents, and c) their role in the management of patients with acute myocardial infarction and in primary and secondary prevention of cardiovascular disease. Platelets interact with both the coagulation and fibrinolytic systems in the pathogenesis of thrombosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Platelet inhibitor agents in cardiovascular disease: an update

Platelets interact with the coagulation and fibrinolytic systems in the maintenance of hemostasis. However, these physiologic mechanisms may become pathologic, requiring prevention and treatment. In this review, the following clinical developments are analyzed: 1) the role of platelets in thrombogenesis; 2) the pharmacology of platelet inhibitory agents; and, most important, 3) the results of recent randomized trials of platelet inhibitor agents in different cardiovascular disorders. Aspirin reduces mortality and infarction rates in unstable angina and significantly decreases vascular mortality in acute myocardial infarction. Platelet inhibitors decrease mortality and recurrent cardiovascular events in the chronic phase after myocardial infarction. They also decrease vein graft occlusion rates after coronary bypass surgery. Although platelet inhibitors are beneficial in preventing acute vessel occlusion during coronary angioplasty, they are ineffective in preventing chronic restenosis. Antiplatelet agents, combined with warfarin, reduce thromboembolic events in patients with a mechanical prosthesis. Platelet inhibitors are also effective in secondary prevention of vascular events in patients with cerebrovascular disease. Finally, the use of aspirin for primary prevention of cardiovascular disease is still evolving, particularly in individuals at high risk. In conclusion, platelet inhibitors are effective in patients with a variety of cardiovascular disorders. The best studied, most inexpensive and least toxic agent is aspirin at a daily dose of 160 to 325 mg. Studies using new platelet inhibitor agents with different mechanisms of action are currently underway.