Aspirin as a therapeutic agent in cardiovascular disease. Special Writing Group

Effect of clopidogrel on tissue-plasminogen activator-induced in vitro thrombolysis of feline whole blood thrombi

OBJECTIVE

To determine if clopidogrel enhanced the thrombolytic rate of tissue-plasminogen activator (t-PA) on an in vitro feline whole blood thrombosis model.

ANIMALS

9 purpose-bred cats.

PROCEDURE

Blood obtained from cats before (baseline) and after treatment with clopidogrel (75 mg, p.o., q 24 h for 3 days) was anticoagulated with sodium citrate (9:1 volume-to-volume ratio) to which 1 microCi of I125-fibrinogen was added. Thrombi were formed by the addition of calcium chloride and bovine thrombin. Thrombi were placed into autologous plasma to which 0.1 mg of t-PA was added. Plasma samples were collected at different time points to determine the amount of released I125-fibrin split products. Thrombolytic rates were calculated by determining the time to 25%, 50%, and 75% thrombolysis (t25, t50, and t75, respectively). Confidence intervals for t25, t50, and t75 at baseline were compared with those after treatment.

RESULTS

There were no significant differences in thrombolytic rates between values obtained at baseline and after clopidogrel treatment (t25, 18.0 vs 18.5 minutes; t50, 63.3 vs 65.6 minutes; and t75, 163.0 vs 170.1 minutes, respectively).

CONCLUSIONS AND CLINICAL RELEVANCE

Clopidogrel did not have an effect on the rate of thrombolysis of feline whole blood thrombi induced by t-PA in this in vitro model.

Role of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitors, angiotensin-converting enzyme inhibitors, cyclooxygenase-2 inhibitors, and aspirin in anti-inflammatory and immunomodulatory treatment of cardiovascular diseases

The immunologic response in atherosclerosis involves not only intrinsic cells of the artery wall, but also circulating leukocytes, lymphocytes, and macrophages. Interaction of various arms of the immune response modulates plaque development and stability, and it is conceivable that immunologic effects of some cardiovascular therapies may contribute to their mechanism of benefit. The preponderance of data has accrued with the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins). Statin effects, such as inhibition of T cell activation, tissue factor expression, or reduction of platelet hyperreactivity, may elicit beneficial effects in vitro and in vivo in patients with coronary artery disease. Moreover, aspirin may limit oxidation of lipoproteins and fibrinogen, and it may inhibit cytokine-induced nitric oxide synthase II expression. The hypothesis that selective inhibition of cyclooxygenase-2 (COX-2) may increase risk of myocardial infarction is controversial and may also be of questionable clinical significance. Finally, angiotensin-converting enzyme (ACE) inhibitors not only reduce proinflammatory mediators, such as interleukin-6, but also enhance the concentration of anti-inflammatory cytokines, such as interleukin-10. Because ACE is expressed at the shoulder region of atherosclerotic plaques, and ACE activity is enhanced in unstable plaques, ACE inhibition may also contribute to plaque stability. This article reviews the potential immunomodulatory potencies of aspirin, COX-2 inhibitors, statins, and ACE inhibitors as established pharmacotherapy in patients with coronary artery disease.

Maintaining the endothelium: preventive strategies for vessel integrity

The endothelium is a diaphanous membrane, only one cell layer thick, that lines all of our blood vessels. Despite its apparent fragility, it exerts profound control over vascular tone, structure, and intersection with circulating blood elements. One of the factors that the endothelium synthesizes is nitric oxide, which is the most potent endogenous vasodilator known. In addition to its blood flow regulating effects, nitric oxide also inhibits key processes in atherosclerosis, including monocyte adherence, platelet aggregation, and proliferation of vascular smooth muscle cells. Nitric oxide synthesis is impaired, and its degradation is accelerated, in many of the conditions associated with atherosclerosis, including hypercholesterolemia. Restoration of nitric oxide synthesis and activity in these disorders can improve blood flow, relieve symptoms, and perhaps reduce the progression of atherosclerosis.(c) 2001 by CHF, Inc.

Differences in endothelial function and morphologic modulation between canine autogenous venous and arterial grafts: endothelium and intimal thickening

BACKGROUND

Late graft failure is still a problem for vascular surgeons. A previous study showed superior patency of arterial grafts compared with venous grafts. In this review we discuss the differences in functional and morphologic modulation of experimental autogenous venous and arterial grafts.

RESULTS

In canine venous grafts, the endothelium of the graft was denuded and recovered within 3 or 4 weeks. In contrast, in arterial grafts, denudation of the endothelium was minimal, and no platelet adherence was observed. Instead, nearly normal intact endothelial cell surface had covered the intima within 3 days after grafting. The histologic findings for arterial grafts thus were quite different from those for venous grafts. Different responses to flow changes between venous and arterial grafts were observed. In the venous grafts, pronounced intimal thickening was associated with impairment of endothelial responses, whereas in the arterial grafts, intact endothelial function and no intimal thickening were observed.

CONCLUSIONS

The intact endothelial function and absence of intimal thickening under the arterial grafts may explain the superior patency of autogenous arterial grafts in comparison with venous grafts.

Microembolic signal counts increase during hyperbaric exposure in patients with prosthetic heart valves

BACKGROUND

Patients with prosthetic heart valves have an increased risk of thromboembolic events, and transcranial Doppler sonography reveals microembolic signals. Whereas microembolic signals were initially assumed to be of particulate matter, recent studies suggest that they are partially gaseous in origin. If this is true, alteration of environmental pressure should change microembolic signal counts. We undertook this study to evaluate the influence of hyperbaric exposure on microembolic signal counts in persons with prosthetic heart valves.

METHODS AND RESULTS

Microembolic signal counts were monitored by transcranial Doppler sonography of both middle cerebral arteries under normobaria (normobaria 1), 2 subsequent periods of hyperbaria (2.5 and 1.75 bar), and a second period of normobaria (normobaria 2) in 15 patients with prosthetic heart valves. Each monitoring period lasted 30 minutes. Compression and decompression rates were 0.1 bar/min. Microembolic signal counts increased from 20 (12-78) at normobaria 1 to 79 (30-165) at 2.5 bar (P <.01 vs normobaria 1 and 2), decreased to 44 (18-128) at 1.75 bar (P <.01 vs normobaria 1 and 2.5 bar; P <.001 vs normobaria 2), and returned to 20 (8-96) at normobaria 2 (values are medians and 95% confidence intervals).

CONCLUSIONS

Our results strongly suggest that gaseous bubbles are underlying material for part of the microembolic signals detected in patients with prosthetic heart valves.

Pharmacological control of platelet function

Advancement in the understanding of the mechanisms of platelet activation, as well as the development of new techniques for studying platelet function, have led to the availability of new classes of platelet inhibiting drugs. Initially, characterization of arachidonic acid metabolism in platelets furthered an understanding of the utility of cyclooxygenase inhibitors, most notably aspirin. The discovery and characterization of platelet receptors such as the adenosine diphosphate (ADP) receptor and glycoprotein IIb/IIIa has been associated with the development of novel classes of anti-platelet drug, such as thienopyridine derivatives and glycoprotein IIb/IIIa receptor antagonists, respectively. Future development in receptor pathway inhibitors also includes glycoprotein Ib/IX as well as the potential use of platelet signaling pathway inhibitors.

Role of Helicobacter pylori infection in gastroduodenal injury and gastric prostaglandin synthesis during long term/low dose aspirin therapy: a prospective placebo-controlled, double-blind randomized trial

OBJECTIVES

Whether gastric infection with Helicobacter pylori increases the risk of gastric mucosal injury during long term/low dose aspirin therapy is unknown. We examined whether H. pylori infection enhances upper GI mucosal damage, assessed endoscopically, in volunteers given low dose aspirin. We studied 61 healthy men and women, 29 with and 32 without active H. pylori infection.

METHODS

We treated volunteers for 45 days with a placebo or aspirin (either 81 mg every day or 325 mg every 3 days). Gastroduodenal mucosal damage was then assessed by endoscopy, as was gastric histology and ex vivo gastric mucosal prostaglandin E2 and F2alpha synthesis rates.

RESULTS

Erosive disease from low dose aspirin (erosions and/or ulcers) occurred in 50% of H. pylori-infected volunteers and in 16% of their noninfected counterparts (p = 0.02). Aspirin caused a significantly higher average mucosal injury score in the gastric antrum in H. pylori-infected participants than in noninfected subjects (p = 0.03), and two H. pylori-infected subjects developed antral gastric ulcers. Subjects with H. pylori gastritis treated with the placebo had nearly 50% higher gastric mucosal prostaglandin (E2 plus F2alpha) synthesis rates than their noninfected counterparts (108 +/- 6 ng/g/min versus 75 +/- 6 ng/g/min, p < 0.001). Aspirin reduced mucosal prostaglandin synthesis to similar levels in infected and noninfected participants.

CONCLUSIONS

Long term/low dose aspirin therapy led to more gastric mucosal damage when H. pylori gastritis was present than when it was absent, despite similar degrees of gastric mucosal prostaglandin depletion.

A comparison of every-third-day versus daily low-dose aspirin therapy on serum thromboxane concentrations in healthy men and women

Aspirin's antithrombotic effect is mediated predominately by inhibition of platelet cyclooxygenase-1, leading to a decline in serum thromboxane A2 concentrations. We performed a placebo-controlled, randomized, double-blind trial to determine whether aspirin could be given at 3-day intervals and still achieve potent serum thromboxane inhibition. One hundred nine healthy men and women with no recent exposure to aspirin and no contraindications to its use participated. Subjects received 325 mg, 81 mg, or 40 mg of plain aspirin every third day, with placebo on other days; 81 mg of aspirin every day; or placebo every day. Serum concentrations of thromboxane B2 (the metabolite of thromboxane A2) were measured at 3-day intervals during a 31-day treatment period, as well as 4, 7, and 14 days after treatment ended. Serum thromboxane B2 concentrations were nearly identical during treatment with 325 mg of aspirin every third day or 81 mg of aspirin per day (86% inhibition [84%, 89%] and 85% inhibition [73%, 96%], respectively). An aspirin dose of 81 mg every third day was nearly as potent (74% inhibition [70%, 79%]), whereas 40 mg of aspirin every third day achieved only 50% inhibition (40%, 60%). Every-third-day low-dose aspirin regimens (325 and 81 mg) deserve comparison with daily low-dose aspirin regimens in controlled clinical trials because the former regimens could prove to have equal efficacy with reduced toxicity.

Temporal trends in the treatment of over 1.5 million patients with myocardial infarction in the US from 1990 through 1999: the National Registry of Myocardial Infarction 1, 2 and 3

OBJECTIVES

We sought to determine trends in the treatment of myocardial infarction from 1990 through 1999 in the U.S. and to relate these trends to current guidelines.

BACKGROUND

Limited data are available to show how recent clinical trials and clinical guidelines have impacted treatment of myocardial infarction.

METHODS

Temporal trends in myocardial infarction treatment and outcome were assessed by using data from 1,514,292 patients in the National Registry of Myocardial Infarction (NRMI) 1, 2 and 3 from 1990 through 1999.

RESULTS

During this interval, the use of intravenous thrombolytic therapy declined from 34.3% to 20.8%, but the use of primary angioplasty increased from 2.4% to 7.3% (both p = 0.0001). The median "door-to-drug" time among thrombolytic therapy recipients fell from 61.8 to 37.8 min (p = 0.0001), primarily owing to shorter "door-to-data" and "data-to-decision" times. The prevalence of non-Q wave infarctions increased from 45% in 1994 to 63% in 1999 (p = 0.0001). From 1994 through 1999, there was increased usage of beta-blockers, aspirin and angiotensin-converting inhibitors, both during the first 24 h after admission and on hospital discharge (all p = 0.0001). Between 1990 and 1999, the median duration of hospital stay fell from 8.3 to 4.3 days, and hospital mortality declined from 11.2% to 9.4% (both p = 0.0001).

CONCLUSIONS

The NRMI data from 1990 through 1999 demonstrate that the recommendations of recent clinical trials and published guidelines are being implemented, resulting in more rapid administration of intravenous thrombolytic therapy, increasing use of primary angioplasty and more frequent use of adjunctive therapies known to reduce mortality, and may be contributing to the higher prevalence of non-Q wave infarctions, shorter hospital stays and lower hospital mortality.

Time course inhibition of gastric and platelet COX activity by acetylsalicylic acid in humans

Aspirin causes peptic ulcers predominately by reducing gastric mucosal cyclooxygenase (COX) activity and prostaglandin synthesis. Because aspirin circulates for only a few hours, we hypothesized that aspirin's inhibitory effect on gastric COX activity must be prolonged. We performed a placebo-controlled experiment in healthy humans to determine the duration of inhibition of aspirin on gastric mucosal COX activity (PGE(2) and PGF(2alpha) synthesis rates). Recovery of gastric COX activity after stopping aspirin was slow and linear. Seventy-two hours after 325-mg aspirin, gastric COX activity was still reduced by 57% (P < 0.001). Duration of inhibition of gastric COX activity was estimated to be 7-8 days after 325-mg aspirin and 5 days after 81-mg aspirin. Recovery of gastric prostaglandin synthesis after 325-mg but not after 81-mg aspirin occurred at slower rates in subjects with Helicobacter pylori-associated gastritis than in those with normal histology. In conclusion, aspirin inhibits gastric COX activity for much longer than predicted from its pharmacokinetic profile, explaining why aspirin at widely spaced intervals is ulcerogenic.

Influencing care in acute myocardial infarction: a randomized trial comparing 2 types of intervention

The purpose of this study was to evaluate performance feedback delivered by on-site presentations compared to mailed feedback on improving acute myocardial infarction (AMI) care. We used a randomized trial including 18 hospitals nested within the Cooperative Cardiovascular Project. Patients comprised AMI Medicare patients admitted before (n = 929, 1994 and 1995) and after intervention (n = 438, 1996). Control hospitals received written feedback by mail. The experimental intervention group received a presentation led by a cardiologist and a quality improvement specialist. We assessed the proportion of patients receiving appropriate AMI care before and after the intervention. Both univariate and multivariate analyses demonstrated no effect of the intervention in increasing the proportion of patients who received reperfusion, aspirin, beta-blockers, or angiotensin-converting enzyme inhibitors. On-site feedback presentations were not associated with a larger improvement in AMI care compared to the mailed feedback. Other interventions, such as opinion leaders and patient-directed interventions, may be necessary in order to improve the care of AMI patients.

Estudo experimental do uso de um antagonista do receptor da glicoproteína IIb/IIIa das placentas na prevenção de tromboses em microanastomoses vasculares

O autor comparou, experimentalmente, a eficácia da droga abciximab, um antagonista do receptor da glicoproteína IIb/IIIa das plaquetas, na prevenção da trombose nas microanastomoses arteriais em ratos Wistar. Utilizou 20 animais, dos quais 10, do grupo controle, receberam solução salina e 10 receberam abciximab, na concentração de 0,8mg/kg, injetados na veia femoral. Trinta minutos após a administração da solução salina ou abciximab, todos os animais foram submetidos ao mecanismo provocador de trombose vascular da artéria femoral do lado oposto ao utilizado para administração da droga, por meio de um trauma externo promovido por aparelho IMPACTOR, desenvolvido pela New York University para padronização de lesão da medula nervosa, o que padronizou a lesão arterial. Todos os animais foram submetidos à microanastomose vascular com mononáilon 10-0, em pontos separados, no local do trauma externo. Foram realizados testes para analisar a perviabilidade vascular da artéria femoral no período de 10, 20 e 30 minutos após o término da anastomose. Após este período, todas as artérias femorais submetidas às microanastomoses foram ressecadas e analisadas em microscopia óptica para avaliar a presença de formação de trombos. Após a análise estatística dos dados, o autor concluiu que o uso do antagonista do receptor da glicoproteína IIb/IIIa das plaquetas diminuiu a incidência de tromboses nas microanastomoses vasculares.

Interaction between the LMWH reviparin and aspirin in healthy volunteers

AIMS

To investigate potential interactions between reviparin and acetylsalicylic acid (ASA 300 mg o.d. from day 1-5).

METHODS

In an open, randomized, three-way-cross over study nine healthy volunteers received reviparin (s.c. injection of 6300 anti-Xa units) or placebo from days 3 to 5 and acetylsalicylic acid (ASA 300 mg) or placebo from days 1 to 5. Assessments included bleeding time (BT), collagen (1 microg ml-1) induced platelet aggregation (CAG), heptest, plasma antifactor Xa-activity and activated partial thromboplastin time (aPTT).

RESULTS

Median bleeding time at day 5 was 5.5 min after reverparin alone and after ASA alone and was 9.6 min after the combination of reviparin and ASA. ASA treatment reduced CAG from 84% to 40 to 50% of Amax; values after combined treatment of reviparin with ASA were not different from those after ASA alone. aPTT was prolonged to 32 s after reviparin; this effect was not modified if subjects received ASA. Combined treatment with ASA and reviparin had no effect on plasma anti-Xa-activity and heptest compared with reviparin alone.

CONCLUSIONS

We could not entirely exclude a small interaction between reviparin and ASA on bleeding time, but the effect is probably without clinical significance.

The mechanisms of coronary restenosis: insights from experimental models

Since its introduction into clinical practice, more than 20 years ago, percutaneous transluminal coronary angioplasty (PTCA) has proven to be an effective, minimally invasive alternative to coronary artery bypass grafting (CABG). During this time there have been great improvements in the design of balloon catheters, operative procedures and adjuvant drug therapy, and this has resulted in low rates of primary failure and short-term complications. However, the potential benefits of angioplasty are diminished by the high rate of recurrent disease. Up to 40% of patients undergoing angioplasty develop clinically significant restenosis within a year of the procedure. Although the deployment of endovascular stents at the time of angioplasty improves the short-term outcome, 'in-stent' stenosis remains an enduring problem. In order to gain an insight into the mechanisms of restenosis, several experimental models of angioplasty have been developed. These have been used together with the tools provided by recent advances in molecular biology and catheter design to investigate restenosis in detail. It is now possible to deliver highly specific molecular antagonists, such as antisense gene sequences, to the site of injury. The knowledge provided by these studies may ultimately lead to novel forms of intervention. The present review is a synopsis of our current understanding of the pathological mechanisms of restenosis.

The salicylate metabolite gentisic acid, but not the parent drug, inhibits glucose autoxidation-mediated atherogenic modification of low density lipoprotein

Oxidation of low density lipoprotein (LDL) by glucose-derived radicals may play a role in the aetiology of atherosclerosis in diabetes. Salicylate was shown to scavenge certain radicals. In the present study, aspirin, salicylate and its metabolites 2,5- and 2, 3-dihydroxybenzoic acid (DHBA) were tested for their ability to impair LDL oxidation by glucose. Only the DHBA derivatives, when present during LDL modification, inhibited LDL oxidation and the increase in endothelial tissue factor synthesis induced by glucose oxidised LDL. The LDL glycation reaction was not affected by DHBA. The antioxidative action of DHBA may be attributed to free radical scavenging and/or chelation of transition metal ions catalysing glucose autoxidation.

Coumadin Aspirin Reinfarction Study: Rationale and Design of the CARS Study

Acute myocardial infarction remains the leading cause of death in the United States. Following increased recognition of the role of thrombosis in the pathogenesis of myocardial infarction, both antiplatelet and anticoagulant therapy have been proven effective in preventing recurrent infarction. However, the optimal antithrombotic regimen remains undetermined. In particular, the role of combination antithrombotic therapy has not been studied. The Coumadin Aspirin Reinfarction Study (CARS) will compare the safety and efficacy of fixed-dose combination Coumadin plus aspirin versus aspirin alone among 8000 survivors of acute myocardial infarction. Patients will be followed for up to 4 years. CARS will provide important information regarding the optimal antithrombotic regimen for myocardial infarct survivors.

A comparative bioavailability study of different aspirin formulations using on-line multidimensional chromatography

A multi-dimensional column chromatographic method employing UV spectrometric detection was optimised and successfully used in a comparative bio-availability study of aspirin obtained from different commercially available oral dosage forms. Sample clean-up was achieved by on-line solid-phase extraction. In this study, the bioavailability of aspirin was compared in plain aspirin tablets, chewed tablets, effervescent tablets and Enteric-coated aspirin tablets. Blood samples were taken at frequent intervals after single dosing in ten healthy volunteers, the plasma samples were first treated with physostigmine sulphate to minimise enzymatic hydrolysis of aspirin to salicylate. The results showed the measured Tmax, Cmax, and AUC was significantly higher for soluble aspirin than for the other formulations and the t1/2 was shorter. This indicates the rapid absorption of aspirin from a soluble formulation compared with that from the other formulations. These differences suggest that the soluble formulation could be the aspirin of choice to treat patients suspected to be at high risk of myocardial infarction. The method performs, in a single step, an efficient extraction and clean-up of aspirin from human plasma. The calibration graph was linear over the calibration range 0.2-12 microg ml(-1) plasma with a limit of detection of 0.1 microg ml(-1). The intra- and inter-assay coefficients of variation were less than 6% and the recoveries ranged from 86 to 98%. The proposed method combines the advantages of being simple and selective in the presence of other potential interfering drugs and is suitable for routine analyses to obtain valuable information about the clinical effects of the drug and its use in prevention treatments of acute myocardial infarction. The whole procedure takes 7 min and is in agreement with other conventional methods.

[Endothelial dysfunction in patients with acute coronary syndrome]

Increased vasoconstriction, activation of platelet vessel wall interaction and invasion of monocytes into the subintima as well as vascular smooth muscle cell proliferation play a fundamental role in the pathogenesis of coronary artery disease. Acute coronary syndromes such as myocardial infarction and unstable angina pectoris are characterized by plaque rupture or erosion, activation of platelets and the coagulation system and vasoconstriction. Endothelial dysfunction may be one of the underlying mechanisms linking coronary artery disease and acute coronary syndromes. Both of these are often temporarily limited. Therefore, "non-invasive examination" of endothelial function by venous occlusion plethysmography or high resolution ultrasound might be useful for monitoring high-risk patients.

Aspirin absorption rates and platelet inhibition times with 325-mg buffered aspirin tablets (chewed or swallowed intact) and with buffered aspirin solution

Large clinical trials such as the second International Study of Infarct Survival routinely gave patients with myocardial infarction a chewed aspirin, yet there are no data to show whether chewing of aspirin is better, or worse, than swallowing a whole tablet. We performed a randomized, placebo-controlled study to determine whether chewing aspirin or administering it in solution accelerates its absorption and antiplatelet activity. On separate days, 12 fasting volunteers ingested 325 mg of buffered aspirin, either by chewing a tablet for 30 seconds before swallowing it with 4 ounces of water, swallowing a whole tablet with 4 ounces of water, or drinking 4 ounces of Alka Seltzer. Frequent blood samples were obtained for serum aspirin, salicylate, and thromboxane B2 (TxB2) concentrations. With all formulations of aspirin, serum TxB2 decreased 50% when the plasma aspirin concentration reached approximately 1,000 ng/ml. A 50% and 90% decrease in serum TxB2 occurred more quickly after chewing a tablet than after a tablet was swallowed whole. For example, the t 50% for serum TxB2 inhibition was 5.0 +/- 0.6 minutes with the chewed tablet versus 12.0 +/- 2.3 minutes when the tablet was swallowed (p = 0.01). A 50% decrease in serum TxB2 occurred 7.6 +/- 1.2 minutes after Alka Seltzer solution (p = 0.04 vs chewing a tablet; p = 0.13 vs swallowing a whole tablet). Chewing an aspirin tablet is the most effective way of accelerating absorption of aspirin into the blood and shortening the time required for an antiplatelet effect.

[Drug therapy for prognostic improvement after acute myocardial infarct]

This review article summarizes the long-term standard therapy for patients with myocardial infarction. The chronic therapy is able to significantly improve quality of life and survival of affected patients. Previous studies showed that in most western countries, the established standard therapy is not given to all patients who would benefit from chronic treatment. The essential parts of today's myocardial infarction treatment consists of effective beta-blockade, inhibition of the angiotensin-conversion enzyme, inhibition of platelet aggregation and lipid lowering agents. This article reviews the clinical benefits which may be expected from each of these therapeutic approaches. Newer, but not yet proven strategies, like blockade of the angiotensin receptor subtype 1 and treatment with antioxidative agents will be discussed.

Effects of tetrandrine and fangchinoline on human platelet aggregation and thromboxane B2 formation

Tetrandrine (TET) and fangchinoline (FAN) are two major components of the radix of Stephania tetrandra. The effects of TET and FAN on human platelet aggregation and formation of thromboxane (TX) B2, a stable metabolite of TXA2, were examined in the aspect of platelet aggregation. TET and FAN inhibited platelet-activating factor (PAF)-induced human platelet aggregation. IC50 values for TET and FAN were 28.6+/-3.24 microM and 21.7+/-2.61 microM, respectively. In the PAF-receptor binding assay, neither TET nor FAN showed any inhibitory effects on the specific bindings of PAF to its receptor. TET and FAN also inhibited PAF-, thrombin- and arachidonic acid-induced thromboxane B2 formation in human washed platelet. These results indicate that TET and FAN inhibit the platelet aggregation by interfering with the intracellular messengers system, but not by inhibiting the binding of PAF to PAF-receptor on the platelet membrane directly, and the suppression of TXA2 formation by TET and FAN may be responsible for their inhibitory activities on the platelet aggregation and further on the thrombosis.

Treatment of stable angina

Severe atherosclerotic narrowing of one or more coronary arteries is responsible for myocardial ischemia and angina pectoris in most patients with stable angina pectoris. The coronary arteries of patients with stable angina also contain many nonobstructive plaques, which are prone to fissures or rupture resulting in presentation of acute coronary syndromes (unstable angina, myocardial infarction, sudden ischemic death). In addition to symptomatic relief of symptoms and an increase in angina-free walking time with antianginal drugs or revascularization procedures, the recent emphasis of treatment has been to reduce adverse clinical outcomes (coronary death and myocardial infarction). The role of smoking cessation, aspirin, treatment of elevated lipids, and treatment of high blood pressure in all patients and of beta-blockers and angiotensin-converting enzyme inhibitors in patients with diminished systolic left ventricular systolic function in reducing adverse outcomes has been well established. What is unknown, however, is whether any anti-anginal drugs (beta-blockers, long-acting nitrates, calcium channel blockers) effect adverse outcomes in patients with stable angina pectoris. Recent trials evaluated the usefulness of suppression of ambulatory ischemia in patients with stable angina pectoris, but it remains to be established whether suppression of ambulatory myocardial ischemia with antianginal agents or revascularization therapy is superior to pharmacologic therapy targeting symptom relief. Patients who have refractory angina despite optimal medical treatment and are not candidates for revascularization procedures may be candidates for newer techniques of transmyocardial revascularization, enhanced external counterpulsation, spinal cord stimulation, or sympathectomy. The usefulness of these techniques, however, needs to be confirmed in large randomized clinical trials.

Low-dose aspirin treatment improves ovarian responsiveness, uterine and ovarian blood flow velocity, implantation, and pregnancy rates in patients undergoing in vitro fertilization: a prospective, randomized, double-blind placebo-controlled assay

OBJECTIVE

To determine the effects of low-dose aspirin on ovarian response, uterine and ovarian blood flow velocity, and implantation and pregnancy rates in patients undergoing IVF.

DESIGN

Prospective, randomized, double-blind placebo-controlled assay.

SETTING

Department of Reproductive Medicine, CER Medical Institute, Buenos Aires, Argentina.

PATIENT(S)

Two hundred ninety-eight infertile patients (mean [+/- SDI age, 35.6+/-4.09 years) undergoing IVF cycles.

INTERVENTION(S)

In the treatment group, 149 patients underwent controlled ovarian hyperstimulation and received a daily dose of 100 mg of aspirin. In the control group, 149 patients underwent controlled ovarian hyperstimulation in association with placebo.

MAIN OUTCOME MEASURE(S)

Number of follicles, number of oocytes retrieved, serum E2 levels, uterine and ovarian pulsatility index, cancellation rate, number of embryos transferred, and implantation and pregnancy rates.

RESULT(S)

There were statistically significant differences between the treatment group and the control group, respectively, in the number of follicles (19.8+/-7.2 versus 10.2+/-5.3), number of oocytes retrieved (16.2+/-6.7 versus 8.6+/-4.6), serum E2 levels (2,923.8+/-1,023.4 versus 1,614.3+/-791.7 pg/mL), uterine pulsatility index (1.22+/-0.34 versus 1.96+/-0.58), ovarian pulsatility index (1.18+/-0.31 versus 1.99+/-0.56), pregnancy rate (45% versus 28%), and implantation rate (17.8% versus 9.2%).

CONCLUSION(S)

Low-dose aspirin treatment significantly improves ovarian responsiveness, uterine and ovarian blood flow velocity, and implantation and pregnancy rates in IVF patients.

Impaired antiplatelet effects of aspirin associated with hypoxia and ATP release from erythrocytes. Studies in a system with flowing human blood

BACKGROUND

We have explored how hypoxic conditions may affect the antiplatelet effects of aspirin.

MATERIALS AND METHODS

For this purpose, a perfusion system containing a damaged vessel segment was modified in order to induce hypoxia (low Po2) in flowing blood. Blood samples were incubated with 50 mumol L-1 aspirin and divided into two aliquots, one being perfused under standard conditions (normoxic) and the other under hypoxic conditions. The interaction of platelets with the subendothelium was morphometrically evaluated.

RESULTS

In studies with untreated blood under normoxic conditions, platelet interaction with the subendothelium was 0.3 +/- 0.1% of contact, 5.3 +/- 1.6% of adhesion, 24.3 +/- 3.3% of thrombus and 29.9 +/- 2.7% of total covered surface. Aspirin-treated blood perfused under normoxic conditions showed a marked decrease in thrombus with a concomitant increase in both platelet adhesion and covered surface percentages. However, when aspirin-treated blood was perfused under hypoxic conditions, platelet interaction was not significantly different from that observed in untreated blood. Hypoxia induced a 10-fold increase in ATP release from erythrocytes in the perfusates. If apyrase was added to the perfusates, ATP release was prevented and aspirin effects were evident again.

CONCLUSION

Our results suggest that, under hypoxic conditions, the presence of aspirin would not help to inhibit further platelet activation.

Effects of aspirin and trapidil on cardiovascular events after acute myocardial infarction. Japanese Antiplatelets Myocardial Infarction Study (JAMIS) Investigators

Aspirin therapy confers conclusive net benefits in the acute phase of evolving myocardial infarction, but no clear evidence of benefit from the long-term use of aspirin after acute myocardial infarction (AMI) has been shown in any single study. This multicenter study, the Japanese Antiplatelets Myocardial Infarction Study, was performed to find out whether aspirin or trapidil would improve clinical outcome compared with no antiplatelets in postinfarction patients. The study was a multicenter, open-label, randomized controlled trial of aspirin 81 mg/day, trapidil 300 mg/day, and no antiplatelets in patients with AMI admitted within 1 month from the onset of symptoms. Seven hundred twenty-three patients were enrolled at 70 hospitals in 18 prefectures of Japan; 250 were randomly assigned to treatment with 81 mg aspirin (aspirin group), 243 to that with trapidil (trapidil group), and 230 were not given antiplatelet agents. The mean follow-up period was 475 days. This study demonstrated that long-term use of aspirin at the dose of 81 mg/day reduced the incidence of recurrent AMI compared with the group receiving no antiplatelets after AMI (p = 0.0045) and that trapidil also reduced the occurrence of reinfarction compared with the group receiving no antiplatelets, but the difference was not significant (p = 0.0810). The incidence of cardiovascular events including cardiovascular death, reinfarction, uncontrolled unstable angina requiring admission to hospital, and nonfatal ischemic stroke was reduced in the group receiving 300 mg trapidil daily compared with the group receiving no antiplatelets (p = 0.0039). The use of aspirin 81 mg/day provided almost no benefit over no antiplatelets therapy in the incidence of cardiovascular events. In conclusion, low-dose aspirin (81 mg) effectively prevented recurrent AMI in postinfarction patients after thrombolysis or coronary angioplasty when used over a long term. Furthermore, the long-term use of trapidil resulted in a significant reduction in the incidence of cardiovascular events.

Salicylate promotes myeloperoxidase-initiated LDL oxidation: antagonization by its metabolite gentisic acid

The oxidative modification of low density lipoprotein (LDL) may play a significant role in atherogenesis. Tyrosyl radicals generated by myeloperoxidase (MPO) can act as prooxidants of LDL oxidation. Taking into consideration, that monophenolic compounds are able to form phenoxyl radicals in presence of peroxidases, we have tested salicylate, in its ability to act as a prooxidant in the MPO system. Measurement of conjugated dienes and lipid hydroperoxides were taken as indicators of lipid oxidation. Exposure of LDL preparations to MPO in presence of salicylate revealed that the drug could act as a catalyst of lipid oxidation in LDL. The radical scavenger ascorbic acid as well as heme poisons (cyanide, azide) and catalase were inhibitory. The main metabolite of salicylic acid, gentisic acid, showed inhibitory action in the MPO system. Even when lipid oxidation was maximally stimulated by salicylate the LDL oxidation was efficaciously counteracted in presence of gentisic acid at salicylate/gentisic acid ratios that could be reached in plasma of patients receiving aspirin medication. Gentisic acid was also able to impair the tyrosyl radical catalyzed LDL peroxidation. The results suggest that salicylate could act like tyrosine via a phenoxyl radical as a catalyst of LDL oxidative modification by MPO. But the prooxidant activity of this radical species is effectively counteracted by the salicylate metabolite gentisic acid.

Production of prostanoids and nitric oxide by infarcted heart in situ and the effect of aspirin

The production of prostacyclin (PGI2) and thromboxane A2 (TXA2) in infarcted and noninfarcted portions of the rabbit heart was studied prior to and following administration of acetylsalicylic acid (aspirin). Aspirin was administered intravenously (iv) as water-soluble Aspisol, d-lysinmono (acetylsalicylate) (Bayer, Leverkusen, Germany) into an ear vein. A branch of the left circumflex coronary artery was ligated. The animals were divided into three groups. The first group received 150 mg/kg/day of aspirin (75 mg/kg of aspirin every 12 h, n = 10). The first administration of aspirin was 1 h after ligation of the coronary artery and the last injection was 1 h before euthanasia. The second group received 5 mg/kg/day of aspirin (every 24 h, n = 10). A separate group of rabbits not receiving aspirin served as controls (n = 12). Two days following onset of ischemia, inducible form of nitric oxide synthase (iNOS) was measured in heart muscle and the oxidation products of nitric oxide (nitrite, NO-2 plus nitrate, NO-3: their sum referred to as NOx) were determined in arterial and coronary venous blood. Concentrations of both PGI2 and TXA2 were elevated in the infarcted portions of the heart compared to the noninfarcted regions. Formation of prostanoids was accompanied by increased activation of iNOS. Both doses of aspirin diminished the concentrations of PGI2 and TXA2 in infarcted heart muscle; in contrast, small doses of aspirin failed to influence myocardial iNOS activity. Apparently small doses of aspirin changed the relationship of iNOS to cyclooxygenase (COX). Coronary arterial-venous difference of NOx and myocardial iNOS activity showed parallel increases. Diminution of prostacyclin by aspirin can damage gastric mucosa and interfere with vasodilatation. Since NO counters these deficiencies, a combination of aspirin with a nitric oxide donor may be advantageous.

Update on aspirin in the treatment and prevention of cardiovascular disease

The effects of low-dose aspirin on cardiovascular disease have been tested in randomized trials in 3 types of populations: (1) patients with a history of cardiovascular disease; (2) patients with evolving acute myocardial infarction (MI), and (3) apparently healthy subjects. In a very wide range of patients with prior occlusive cardiovascular disease, aspirin reduces the risks of nonfatal MI, nonfatal stroke, and vascular death. Initiating aspirin therapy within 24 hours after the onset of symptoms of an acute MI also confers conclusive reductions in the risk of nonfatal reinfarction, nonfatal stroke, and total cardiovascular death. In primary prevention trials, aspirin has been shown to reduce the risk of a first MI in men, but the data on stroke and total cardiovascular death are not sufficient to allow firm conclusions to be drawn; randomized data from studies in women are not yet available. The Women's Health Study, an ongoing large-scale trial in female health care professionals, will provide the data necessary to assess the balance of benefits and risks of aspirin in primary prevention. Until then, the decision to use aspirin in primary prevention should be based on the clinical judgment of the physician and considered as an adjunct in the management of other cardiovascular disease risk factors.

Antiplatelet therapy for secondary stroke prevention

The precise role of antiplatelet therapy in secondary stroke prevention remains a matter of some debate. Although specific antiplatelet agents (notably aspirin, ticlopidine, dipyridamole, and clopidogrel) have been shown to be active in the prevention of secondary stroke, questions remain about the effective dose of these agents and their potential efficacy in combined therapeutic regimens. In addition, haematological and gastrointestinal side-effects of antiplatelet agents remain a significant clinical concern for patients and prescribing physicians. This review article examines research on both monotherapy and combination antiplatelet therapy for secondary stroke prevention, with an emphasis on lessons learned about dosage schedules, treatment protocols, and side-effect profiles.

Salicylate inhibits LDL oxidation initiated by superoxide/nitric oxide radicals

Simultaneously produced superoxide/nitric oxide radicals (O2*-/NO*) could form peroxynitrite (OONO-) which has been found to cause atherogenic, i.e. oxidative modification of LDL. Aromatic hydroxylation and nitration of the aspirin metabolite salicylate by OONO- has been reported. Therefore we tested if salicylate may be able to protect LDL from oxidation by O2*-/NO* by scavenging the OONO reactive decomposition products. When LDL was exposed to simultaneously produced O2*-/NO* using the sydnonimine SIN-1, salicylate exerted an inhibitory effect on LDL oxidation as measured by TBARS and lipid hydroperoxide formation and alteration in electrophoretic mobility of LDL. The cytotoxic effect of SIN-1 pre-oxidised LDL to endothelial cells was also diminished when salicylate was present during SIN-1 treatment of LDL. Spectrophotometric analysis revealed that salicylate was converted to dihydroxybenzoic acid (DHBA) derivatives in the presence of SIN-1. 2,3- and 2,5-DHBA were even more effective to protect LDL from oxidation by O2*-/NO*. Because O2*-/NO* can occur in vivo, the results may indicate that salicylate could act as an efficacious inhibitor of O2*-/NO* initiated atherogenic LDL modification, thus further supporting the rationale of aspirin medication regarding cardiovascular diseases.

Rationale and design of the Arterial Disease Multiple Intervention Trial (ADMIT) pilot study

The primary objectives of the pilot study were to: (1) evaluate the feasibility of recruiting patients with peripheral arterial disease (PAD); (2) measure the efficacy and safety of high-density lipoprotein (HDL)-raising treatment, low-density lipoprotein (LDL)-lowering therapy, antioxidant therapy, antithrombotic therapy, and their combinations; and (3) assess adherence to a complex multiple drug regimen. Secondary objectives included measurement of the effect of the interventions on prespecified biochemical markers, maintenance of therapy masking (in particular with niacin), and measurement of the intervention's impact on functional status and on quality of life. To date, no secondary prevention trial has been conducted specifically among patients with PAD. Intermittent claudication affects about 0.5% to 1.0% of persons aged >35 years. There is a striking increase in incidence of PAD with age, particularly among those aged >50 years in both sexes, although men are twice as likely as women to develop PAD. The Arterial Disease Multiple Intervention Trial was a double-blind randomized pilot trial of 468 participants with documented PAD. A 2 x 2 x 2 factorial design was used to evaluate the effect of 3 interventions. The pilot incorporated several major novel design features: first, the use of a simple noninvasive method (measurement of ankle brachial index) to identify a population with either symptomatic or asymptomatic PAD; and second, a lipid modifying strategy to increase HDL with nicotinic acid in the intervention group while lowering LDL levels equally with an hydroxymethylglutaryl-coenzyme A reductase inhibitor as needed in the intervention and control group. Two other arms, the antioxidant arm (consisting of beta-carotene and vitamins E and C) and the antithrombotic arm (using warfarin) were also added. Adherence to therapy was measured by pill count, and success in treatment was measured by the proportion of values in target range for HDL, LDL, and the international normalized ratio.

Aspirin for primary prevention of cardiovascular events

OBJECTIVE

The use of aspirin for primary prevention of cardiovascular events in the general population is controversial. The purpose of this study was to create a versatile model to evaluate the effects of aspirin in the primary prevention of cardiovascular events in patients with different risk profiles.

DESIGN

A Markov decision-analytic model evaluated the expected length and quality of life for the cohort's next 10 years as measured by quality-adjusted survival for the options of taking or not taking aspirin.

SETTING

Hypothetical model of patients in a primary care setting.

PATIENTS

Several cohorts of patients with a range of risk profiles typically seen in a primary care setting were considered. Risk factors considered included gender, age, cholesterol levels, systolic blood pressure, smoking status, diabetes, and presence of left ventricular hypertrophy. The cohorts were followed for 10 years. Outcomes were myocardial infarction, stroke, gastrointestinal bleed, ulcer, and death.

MAIN RESULTS

For the cases considered, the effects of aspirin varied according to the cohort's risk profile. By taking aspirin, the lowest-risk cohort would be the most harmed with a loss of 1.8 quality-adjusted life days by taking aspirin; the highest risk cohort would achieve the most benefit with a gain of 11.3 quality-adjusted life days. Results without quality adjustment favored taking aspirin in all the cohorts, with a gain of 0.73 to 8.04 days. The decision was extremely sensitive to variations in the utility of taking aspirin and to aspirin's effects on cardiovascular mortality. The model was robust to other probability and utility changes within reasonable parameters.

CONCLUSIONS

The decision of whether to take aspirin as primary prevention for cardiovascular events depends on patient risk. It is a harmful intervention for patients with no risk factors, and it is beneficial in moderate and high-risk patients. The benefits of aspirin in this population are comparable to those of other widely accepted preventive strategies. It is especially dependent on the patient's risk profile, patient preferences for the adverse effects of aspirin, and on the level of beneficial effects of aspirin on cardiovascular-related mortality.

Recent antiplatelet drug trials in the acute coronary syndromes. Clinical interpretation of PRISM, PRISM-PLUS, PARAGON A and PURSUIT

This paper reviews the results of 4 recent clinical trials, Platelet Receptor inhibition for Ischaemic Syndrome Management (PRISM), Platelet Receptor inhibition for Ischaemic Syndrome Management in Patients Limited to very Unstable Signs and symptoms (PRISM-PLUS), Platelet IIb/IIIa Antagonist for the Reduction of Acute coronary syndrome events in a Global Organisation Network (PARAGON A), and Platelet IIb/IIIa in Unstable angina Receptor Suppression Using Integrilin Therapy (PURSUIT), that have investigated the use of glycoprotein (GP) IIb/IIIa inhibitors in with non-ST-segment elevation acute coronary syndromes. The PRISM trial randomised 3232 patients with non-ST-elevation acute coronary syndromes to either tirofiban or heparin. Patients receiving tirofiban had a 32% reduction in the likelihood of death, myocardial infarction (MI) or refractory ischaemia at 48 hours and a 36% reduction in death at 30 days (2.3 vs 3.6%, p = 0.02). The PRISM-PLUS trial randomised 1915 patients with severe non-ST-elevation acute coronary syndromes to either tirofiban alone, heparin alone or the combination of tirofiban and heparin. Patients treated with the combination of tirofiban and heparin had a 27% reduction in death or nonfatal MI at 30 days (8.7 vs 11.9%, p = 0.027). The PARAGON A trial randomised 2282 patients with non-ST-elevation acute coronary syndromes to either high or low dose lamifiban, with or without heparin, or heparin alone. There was no reduction in the rate of death at day 30 or nonfatal MI in patients who received lamifiban; however, at 6 months a significant treatment effect was seen in patients who received low dose lamifiban (13.7%, p = 0.02) but not high dose lamifiban (16.4%, p = 0.38) compared with those who received heparin alone (18.1%). The PURSUIT trial randomised 10,948 patients with non-ST-elevation acute coronary syndromes to either eptifibatide or placebo. Patients receiving eptifibatide had a 9.6% relative, and 1.5% absolute, reduction in death or MI at 30 days (15.7 vs 14.2%, p = 0.04). GP IIb/IIIa inhibitors are revolutionising the way we treat patients with atherosclerotic coronary artery disease. The results of these trials demonstrate that the GP IIb/IIIa inhibitors tirofiban, lamifiban, and eptifibatide are beneficial in the non-ST-elevation acute coronary syndrome population. In the future, acute therapy with an intravenous GP IIb/IIIa inhibitor followed by long term administration of an oral GP IIb/IIIa inhibitor may be the cornerstone of the management of patients with acute coronary syndromes.

Cooperative Cardiovascular Project (CCP) quality improvement in Maine, New Hampshire, and Vermont

The Cooperative Cardiovascular Project (CCP) is a nationwide quality improvement project (quality indicator measurement, feedback, remeasurement) in Medicare acute myocardial infarction (AMI) patients sponsored by the Health Care Financing Administration (HCFA). In Maine, New Hampshire, and Vermont, 3,472 baseline records were abstracted from 76 hospitals from January 1994 to February 1995. After feedback, 2,270 remeasurements were collected from October 1996 to May 1997. At remeasurement, performance improved significantly for "ideal" candidates (defined by the CCP) on five quality indicators--aspirin during hospitalization 88% to 93% (p < .001), thrombolytic timing 60% to 69% (p < .01), discharge aspirin 83% to 90% (p < .001), discharge beta-blockers 69% to 82% (p < .01), and calcium channel blocker avoidance 83% to 93% (p < .05). Reperfusion, angiotensin converting enzyme inhibitors, and smoking cessation advice did not improve significantly. This study demonstrates that evidence-based indicators, nationally designed data collection, and locally based interventions can significantly improve AMI care.

Acute interventions for myocardial reperfusion

The primary goal of treatment in acute myocardial infarction is reperfusion of the infarct-related artery in as short a time as possible. Present strategies for acute reperfusion include the use of thrombolytic agents and a variety of catheter-based interventions. This article presents a brief review of these strategies and discusses the patient subsets better served by a particular type of intervention.

Effective long-term inhibition of thromboxane production but not of serotonin release in patients with coronary heart disease by 30 mg/d acetylsalicylic acid dosage

Efficacy of aspirin (Acetylsalicylic acid, ASA) antiaggregatory prevention was demonstrated in a series of clinical trials. The recommended ASA doses decreased gradually and doses 50-30 mg ASA/d are intensively studied at the present time. A group of 42 patients with coronary heart disease was evaluated: (1) Basal TXB2 production during spontaneous blood clotting was 360 +/- 37.6 ng/ml; (2) Two initial doses were tested: while 200 mg ASA inhibited, during spontaneous blood clotting, median TXB2 production by 99.9% (serum TXB2 concentration 1.35 ng/ml), 30 mg ASA median inhibition was just 42.0% (serum TXB2 151 ng/ml); (3) 30 mg ASA/d maintenance dose was evaluated for 3 months. The median TXB2 production inhibition was 98.5% (serum TXB2 3.75 ng/ml, first month) and 94.0% (serum TXB2 14.2 ng/ml, third month); (4) Four patients did not respond sufficiently, because of noncompliance verified by the determination of salicyluric acid urinary excretion, the lower limit of excretion being <3 micromol/2 h; (5) Both initial and maintenance ASA dose decreased metabolic TXA2 endproducts in urine; (6) 5HT platelet release did not decrease; (7) Potential changes of 5HT metabolic elimination were excluded by the simultaneous determination of 5-hydroxyindoleacetic acid (5HIAA). In conclusion, 200 mg initial dose and 30 mg ASA/d maintenance dose are suggested to be maximally inhibitory for TXB2 production without influence on 5HT release.

Antiplatelet therapy in atherosclerotic cardiovascular disease

Arterial thrombosis frequently leads to death or disability from stroke, peripheral arterial disease, or myocardial infarction (MI). Treating the underlying causes of these diseases is the key to producing significant reduction in morbidity, mortality, and health care costs. Prevention of arterial thrombosis is the primary indication for antiplatelet therapy, and intense research has been conducted in the past decade to develop novel antiplatelet agents with favorable safety profiles. The results of the Antiplatelet Trialists' Collaboration, which definitively established the rationale for antiplatelet agents in the prevention of death, MI, and stroke, were an important stimulus for this research. This large meta-analysis combined data from 145 randomized trials and showed that antiplatelet therapy (most commonly aspirin, 75 to 325 mg/d) reduced the risk of vascular events, including nonfatal MI, nonfatal stroke, and vascular death, by 25% in patients at high risk for occlusive vascular disease. The limitations and adverse effects associated with traditional antiplatelet agents such as aspirin have prompted the search for newer antiplatelet agents. Clinical trials such as the Clopidogrel versus Aspirin in Patients at Risk of Ischemic Events (CAPRIE) study, which was the first study to evaluate aspirin and clopidogrel in patients with cerebrovascular, cardiac, and peripheral arterial disease, have established the importance of newer antiplatelet effects in the management of patients with diseases associated with atherosclerosis. The pathophysiology of atherosclerosis, the mechanisms of action of antiplatelet agents, and the results of these and other clinical trials that document the value of antiplatelet agents in atherosclerosis are reviewed in this paper.

Thrombolytic Therapy in Acute Myocardial Infarction Part II: 1997 Update

Thrombolytic therapy has become an established treatment for acute myocardial infarction. Streptokinase was first demonstrated in 1988 to reduce mortality rates. In 1993, tissue plasminogen activator was shown to have a slight superiority over streptokinase in reducing mortality rates (approximately 1%). Reteplase is a second generation thrombolytic agent that is given in two bolus injections intravenously over 30 minutes. Studies demonstrated slightly better and more rapid improvement in myocardial perfusion with reteplase compared to tissue plasminogen activator. However, recent studies showed 30-day mortality rates in patients treated with reteplase were similar as those treated with tissue plasminogen activator. The use of angioplasty, aspirin, beta blockers, angiotensin converting enzyme inhibitors, and lipid lowering agents also contribute to the reduction of mortality from acute myocardial infarction.

Aspirin protects endothelial cells from oxidative stress--possible synergism with vitamin E

A 24-h incubation with hydrogen peroxide (0.65 mM) markedly reduced viability of cultured endothelial cells. Preincubation with aspirin (3-30 microM) protected endothelial cells from hydrogen peroxide-induced toxicity and increased viability in a concentration-dependent fashion by up to 64% of control. A similar protection was observed with D-alpha-tocopherol acetate (vitamin E, 3-30 microM). The cytoprotective effects of aspirin and vitamin E against hydrogen peroxide were overadditive suggesting different mechanisms of antioxidant action. In agreement with this, cytotoxicity induced by iron, the main catalyst of oxygen radical formation, was substantially reduced by aspirin but not vitamin E. These results show that aspirin protects endothelial cells from oxidative stress possibly via binding or chelation of free cytosolic iron. Moreover, a combination of aspirin and vitamin E might be useful for the prevention of endothelial injury in cardiovascular disease, e.g. during atherogenesis.

Influence of aspirin usage on blood pressure: dose and administration-time dependencies

This study investigates the possible effects of acetylsalicylic acid (ASA; aspirin) on systolic (S) and diastolic (D) blood pressure (BP) in healthy and mildly hypertensive subjects receiving ASA at different times according to their rest-activity cycle. A double-blind, randomized, controlled trial was conducted in 73 healthy young adult volunteers and 18 previously untreated subjects with mild hypertension. The BP of each subject was automatically monitored every 30 minutes for 48h before the trial and at the end of a one-week course of placebo and a one-week course of ASA. Healthy volunteers were randomly assigned to one of six groups, defined according to the dose of ASA (either 500 mg/day, the usual commercial dose; or 100 mg/day) and timing of ASA and placebo (within 2h after awakening, Time 1; 7h to 9h after awakening, Time 2; or within 2h of bedtime, Time 3). Subjects with mild hypertension received the low dose of 100 mg/day ASA, as well as one week of placebo, and were randomly assigned to one of the same three groups defined above according to the time of treatment. A small (approximately 2 mmHg in the 24h mean of SBP), but statistically significant, BP reduction was found when 500 mg/day ASA was given to healthy volunteers at Time 2. With 100 mg/day, the effect of ASA in healthy subjects was comparable to the BP reduction found with the higher dose for Time 2; there was again no effect on BP at Time 1, but we found a statistically significant effect at Time 3 (2.3 mmHg reduction in the 24h mean of SBP), larger than for Time 2. For hypertensive patients, the BP reduction was again statistically significant for Time 2 and, to a greater extent, for Time 3 (approximately 4.5 mmHg for both SBP and DBP); all patients in these two groups showed a BP reduction after one week of ASA. The effect was about three times as large as the BP reduction obtained in healthy subjects treated with 100 mg/day ASA. Results indicate a statistically significant time- and dose-dependent effect of ASA on BP. In any meta-analysis of ASA effects, inquiries about the time when subjects took the drug are indicated and may account for discrepancies in the literature. Moreover, the influence of ASA on BP demonstrated here indicates the need to identify and control for ASA effects in patients using ASA before and during their participation in antihypertension medication trials.

Could salicylates in food have contributed to the decline in cardiovascular disease mortality? A new hypothesis

OBJECTIVES

The prophylactic effect of aspirin (at 80 mg/day) for the prevention of cardiovascular disease mortality has long been recognized. This study examined whether other salicylates are present in comparable quantities in the US food supply.

METHODS

To estimate the order of magnitude for salicylates in the food supply, annual production data for selected synthetic salicylates were analyzed.

RESULTS

Production figures for 1960 indicate exposure to salicylates of 250 mg/day per person, or 95 mg/day per person excluding aspirin. Trend data indicate a rise in the production of salicylates over time, reaching 341 mg/day per person, or 126 mg/day per person excluding aspirin, in 1970.

CONCLUSIONS

The US ingestion of salicylates with aspirinlike properties may have increased to the point that many susceptible individuals have received a beneficial effect that has contributed to the decline in cardiovascular disease mortality.

Atherosclerotic risk factors are less intensively treated in patients with peripheral arterial disease than in patients with coronary artery disease

OBJECTIVE

To compare rates of therapy for atherosclerotic risk factors between patients with lower extremity peripheral arterial disease (PAD) and patients with coronary artery disease (CAD).

DESIGN

Cross-sectional.

SETTING

Academic medical center.

PATIENTS/PARTICIPANTS

Three hundred forty-nine consecutive patients diagnosed with PAD or CAD identified from the blood flow and cardiac catheterization laboratories, respectively.

MEASUREMENTS AND MAIN RESULTS

Participants were interviewed by telephone for medical history as well as therapies prescribed and recommended by their physicians. Among patients with hypercholesterolemia, more CAD patients were taking cholesterol-lowering drugs (58% vs 46%, p = .08) and more CAD patients recalled a physician's instruction to follow a low-fat, low-cholesterol diet (94% vs 83%, p = .01). CAD patients were more likely to exercise regularly (71% vs 50%, p < .01). Among patients not exercising, more CAD patients recalled a physician's advice to exercise (74% vs 47%, p < .01). In logistic regression analysis, hypercholesterolemic patients with exclusive CAD were more likely to be treated with drug therapy (odds ratio [OR] 2.3, p = .05). CAD patients were more likely to recall advice to exercise (OR 4.0, p < .001), and more likely to be taking aspirin or warfarin (OR 4.8, p = .01).

CONCLUSIONS

Atherosclerotic risk factors are less intensively treated among PAD patients than CAD patients. A number of possible explanations could account for these disparities in therapeutic intensity.

Acetylsalicylate and salicylates in foods

Acetylsalicylic acid is effective in the prevention of cardiovascular disease. It was suggested that fruits and vegetables provide unknown amounts of acetylsalicylic acid. We could not find any acetylsalicylic acid in 30 foods using HPLC with fluorescence detection (detection limits: 0.02 mg/kg for fresh, and 0.2 mg/kg for dried products). We showed that urinary excretion of salicylates is a valid indicator for intake, and found a median salicylate excretion of 10 micromol (1.4 mg) in 24 h urine of 17 volunteers eating a variety of diets. Our data suggest that the content of (acetyl)salicylic acid of diets may be too low to affect disease risk.

Preventive medicine and screening in older adults

PURPOSE

To review important current issues, studies, recommendations and controversies relating to preventive medicine and screening in older people. STUDY SELECTION/DATA ABSTRACTION: MEDLINE searches for literature on prevention and screening with regard to older adults as well as each individual condition reviewed; bibliographical reviews of textbooks, journal articles, government and advocacy organization task force reports, and recommendations. Important information synthesized and discussed qualitatively.

DATA SYNTHESIS

Data and recommendations are presented for most common preventive services, including primary prevention and screening for cardiovascular diseases and risk factors, common malignancies, endocrine and infectious diseases, osteoporosis, sensory deficits, and dementia.

CONCLUSIONS

The goal of preventive medicine in older people should be not only reduction of premature morbidity and mortality but preservation of function and quality of life. Attempts to prevent diseases of old age should start in youth; the older the patient, the less likely the possibility or value of primary and secondary prevention, and the greater the stress must be on tertiary prevention. Age 85 is proposed as a general cutoff range beyond which conventional screening tests are unlikely to be of continued benefit; however, care must always be individualized. Emphasis should be on offering the best proven and most effective interventions to the individuals at highest risk of important problems such as cardiovascular diseases, malignancies, infectious and endocrine diseases, and other important threats to function in older people. Breast cancer screening, smoking cessation, hypertension treatment, and vaccination for infectious diseases are thus far among the most firmly proven and well accepted specific preventive measures, with physical exercise also being particularly promising. Although more research is needed, a current working approach is necessary and possible. A summary table of recommendations and information tools such as reminders or flowsheets may be valuable in helping the physician carry out prevention and screening programs.

Hypoxia induces cyclooxygenase-2 via the NF-kappaB p65 transcription factor in human vascular endothelial cells

The inducible cyclooxygenase, COX-2, has been associated with vascular inflammation and cellular proliferation. We have discovered that hypoxia increases expression of the COX-2 gene in human vascular endothelial cells in culture independent of other stimuli. Western analysis of human umbilical vein endothelial cells (HUVEC) revealed a greater than 4-fold induction of protein by hypoxia (1% O2). The steady-state level of COX-2 mRNA was correspondingly elevated by both Northern blot and reverse transcriptase-polymerase chain reaction analysis. Using electrophoretic mobility shift assays with antibody supershifting, we also found that hypoxia causes increased binding of NF-kappaB p65 (Rel A) to the one out of the two NF-kappaB consensus elements in the COX-2 promoter which is closest to the transcription start site of the COX-2 gene. Transfection of an immortalized human microvascular endothelial cell line (HMEC-1) with mutation reporter gene constructs and HUVEC with both mutation and deletion reporter gene constructs suggested that transcription of the COX-2 gene was enhanced by hypoxia. In transcription factor decoy experiments, hypoxic HUVEC were exposed in culture to 20 microM of the same NF-kappaB element found to bind NF-kappaB protein. The wild type transcription factor decoy prevented hypoxic induction of COX-2, presumably by binding with cytoplasmic p65; however, mutated or scrambled oligonucleotides did not prevent the increase in COX-2 protein expression by hypoxia. Thus, the intracellular signaling mechanism that leads to induction of COX-2 by hypoxia includes binding of p65 to the relatively 3' NF-kappaB consensus element in the COX-2 upstream promoter region in human vascular endothelial cells.