Effect of aspirin in large doses on attacks of variant angina

Recurrent syncope driven by unique-variant angina pectoris

The patient's vasospastic variant angina manifested as syncope with asymptomatic ischemic episodes, and repeated 24-h dynamic electrocardiogram and coronary angiography examinations combined with coronary provocation spasm tests were necessary for its diagnosis and management.

Vasospastic angina: a review on diagnostic approach and management

Vasospastic angina (VSA) refers to chest pain experienced as a consequence of myocardial ischaemia caused by epicardial coronary spasm, a sudden narrowing of the vessels responsible for an inadequate supply of blood and oxygen. Coronary artery spasm is a heterogeneous phenomenon that can occur in patients with non-obstructive coronary arteries and obstructive coronary artery disease, with transient spasm causing chest pain and persistent spasm potentially leading to acute myocardial infarction (MI). VSA was originally described as Prinzmetal angina or variant angina, classically presenting at rest, unlike most cases of angina (though in some patients, vasospasm may be triggered by exertion, emotional, mental or physical stress), and associated with transient electrocardiographic changes (transient ST-segment elevation, depression and/or T-wave changes). Ischaemia with non-obstructive coronary arteries (INOCA) is not a benign condition, as patients are at elevated risk of cardiovascular events including acute coronary syndrome, hospitalization due to heart failure, stroke and repeat cardiovascular procedures. INOCA patients also experience impaired quality of life and associated increased healthcare costs. VSA, an endotype of INOCA, is associated with major adverse events, including sudden cardiac death, acute MI and syncope, necessitating the study of the most effective treatment options currently available. The present literature review aims to summarize current data relating to the diagnosis and management of VSA and provide details on the sequence that treatment should follow.

Pharmacotherapy in patients with vasomotor disorders

Background

Anginal symptoms in patients with non-obstructive coronary artery disease are frequently related to vasomotor disorders of the coronary circulation. Although frequently overlooked, a distinct diagnosis of different vasomotor disorders can be made by intracoronary function testing. Early detection and treatment seems beneficial, but little evidence is available for the medical treatment of these disorders. Nevertheless, there are several pharmacotherapeutic options available to treat these patients and improve quality of life.

Methods & findings

We performed an extensive yet non-systematic literature search to explore available pharmacotherapeutic strategies for addressing vasomotor disorders in individuals experiencing angina and non-obstructive coronary artery disease. This article presents a comprehensive overview of therapeutic possibilities for patients exhibiting abnormal vasoconstriction (such as spasm) and abnormal vasodilation (like coronary microvascular dysfunction).

Conclusion

Treatment of vasomotor disorders can be very challenging, but a general treatment algorithm based on the existing evidence and the best available current practice is feasible.

MINOCA: One Size Fits All? Probably Not—A Review of Etiology, Investigation, and Treatment

Myocardial infarction with non-obstructive coronary arteries (MINOCA) is a heterogeneous group of conditions that include both atherosclerotic (coronary plaque disruption) and non-atherosclerotic (spontaneous coronary artery dissection, coronary artery spasm, coronary artery embolism, coronary microvascular dysfunction, and supply–demand mismatch) causes resulting in myocardial damage that is not due to obstructive coronary artery disease. Failure to identify the underlying cause may result in inadequate and inappropriate therapy in these patients. The cornerstone of managing MINOCA patients is to identify the underlying mechanism to achieve the target treatment. Intravascular imaging is able to identify different morphologic features of coronary plaques, while cardiac magnetic resonance is the gold standard for detection of myocardial infarction in the setting of MINOCA. In this review, we summarize the relevant clinical issues, contemporary diagnosis, and treatment options of MINOCA.

Outpatient Management of Patients With Angina With No Obstructive Coronary Arteries: How to Come to a Proper Diagnosis and Therapy

Two-thirds of women and one-third of men who undergo a clinically indicated coronary angiography for stable angina, have no obstructive coronary artery disease (CAD). Coronary vascular dysfunction is a highly prevalent underlying cause of angina in these so called “Angina with No Obstructive Coronary Arteries (ANOCA)” patients, foremost in middle aged women. Coronary vascular dysfunction encompasses various endotypes, namely epicardial and microvascular coronary spasms, impaired vasodilatation, and increased microvascular resistance. ANOCA patients, especially those with underlying coronary vascular dysfunction, have an adverse cardiovascular prognosis, poor physical functioning, and a reduced quality of life. Since standard ischemia detection tests and coronary angiograms are not designed to diagnose coronary vascular dysfunction, this ischemic heart disease is often overlooked and hence undertreated. But adequate diagnosis is vital, so that treatment can be started to reduce symptoms, reduce healthcare costs and improve quality of life and cardiovascular prognosis. The purpose of this review is to give a contemporary overview of ANOCA with focus on coronary vascular dysfunction. We will provide a possible work-up of patients suspected of coronary vascular dysfunction in the outpatient clinical setting, based on the latest scientific insights and international consensus documents. We will discuss the value of ischemia detection testing, and non-invasive and invasive methods to diagnose coronary vascular dysfunction. Furthermore, we will go into pharmacological and non-pharmacological therapeutic options including anti-anginal regimens and lifestyle interventions.

Angina due to coronary artery spasm (variant angina): diagnosis and intervention strategies

INTRODUCTION

Since Prinzmetal first described a 'variant' form of angina pectoris, with predominantly resting episodes of pain and cyclic severity variations, it has gradually become apparent that this clinical presentation is caused by episodes of coronary artery spasm (CAS) involving focal or diffuse changes in large and/or small coronary arteries in the presence or absence of 'fixed' coronary artery stenoses. However, most clinicians have only limited understanding of this group of disorders.

AREAS COVERED

We examine the clinical presentation of CAS, associated pathologies outside the coronary vasculature, impediments to making the diagnosis, provocative diagnostic tests, available and emerging treatments, and the current understanding of pathogenesis.

EXPERT OPINION

CAS is often debilitating and substantially under-diagnosed and occur mainly in women. Many patients presenting with CAS crises have non-diagnostic ECGs and normal serum troponin concentrations, but CAS can be suspected on the basis of history and association with migraine, Raynaud's phenomenon and Kounis syndrome. Definitive diagnosis requires provocative testing at coronary angiography. Treatment still centers around the use of calcium antagonists, but with greater understanding of pathogenesis, new management options are emerging.

Impact of aspirin use on clinical outcomes in patients with vasospastic angina: a systematic review and meta-analysis

OBJECTIVES

The use of aspirin to prevent cardiovascular disease in vasospastic angina (VSA) patients without significant stenosis has yet to be investigated. This study aimed to investigate the efficacy of aspirin use among VSA patients.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, Web of Science and Cochrane Central Register of Controlled Trials were searched for relevant information prior to October 2020.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Aspirin use versus no aspirin use (placebo or no treatment) among VSA patients without significant stenosis.

DATA EXTRACTION AND SYNTHESIS

Two investigators extracted the study data. ORs and 95% CIs were calculated and graphed as forest plots. The Newcastle-Ottawa Quality Assessment Scale tool and Begg's funnel plot were used to assess risk of bias.

RESULTS

Four propensity-matched cohorts, one retrospective analysis and one prospective multicentre cohort, in total comprising 3661 patients (aspirin use group, n=1695; no aspirin use group, n=1966) were included in this meta-analysis. Aspirin use and the incidence of major cardiovascular adverse events with follow-up of 1-5 years were not significantly correlated (combined OR=0.90, 95% CI: 0.55 to 1.68, p=0.829, I²=82.2%; subgroup analysis: OR=1.09, 95% CI: 0.81 to 1.47, I²=0%). No significant difference was found between aspirin use and the incidence of myocardial infarction (OR=0.62, 95% CI: 0.09 to 4.36, p=0.615, I²=73.8%) or cardiac death (OR=1.73, 95% CI: 0.61 to 4.94, p=0.444, I²=0%) during follow-up.

CONCLUSION

Aspirin use may not reduce the risk of future cardiovascular events in VSA patients without significant stenosis.

PROSPERO REGISTRATION NUMBER

CRD42020214891.

Clopidogrel plus Aspirin Use is Associated with Worse Long-Term Outcomes, but Aspirin Use Alone is Safe in Patients with Vasospastic Angina: Results from the VA-Korea Registry, A Prospective Multi-Center Cohort

Anti-platelet agents are commonly used in vasospastic angina (VA) patients with comorbidity like coronary artery disease. However, long-term clinical outcomes in the use of aspirin, clopidogrel or the two agents together have rarely been investigated in VA patients. In a prospective study, we enrolled 2960 patients who received coronary angiography and ergonovine provocation test at 11 university hospitals in Korea. Among them, 1838 patients were diagnosed either with definite (n = 680) or intermediate (n = 1212) VA, using the criteria of chest pain, ECG changes and ergonovine provocation test results. They were analyzed according to their use of aspirin, clopidogrel or both, or no anti-platelet agent at all. The primary outcome was time to composite events of death from any cause, acute coronary syndrome (ACS) and symptomatic arrhythmia during a 3-year follow-up. A primary composite outcome was significantly more common in the aspirin plus clopidogrel group, at 10.8% (14/130), as compared with the non-antiplatelet group, at 4.4% (44/1011), (hazard ratio [HR] 2.41, 95% confidence interval [CI], 1.32–4.40, p = 0.004). With regard to the person-time event rate, similar results were shown, with the highest rate in the aspirin plus clopidogrel user at 4.72/1000 person months (95% CI, 2.79–7.96, log-rank test for primary outcome p = 0.016). The person-time event of the ACS rate was also highest in that group, at 2.81 (95% CI, 1.46–5.40, log-rank test for ACS p = 0.116). Kaplan-Meier survival analysis demonstrated poor prognosis in primary outcomes and ACS in aspirin plus clopidogrel users (log-rank test, p = 0.005 and p = 0.0392, respectively). Cox-proportional hazard regression analysis, adjusting for age, sex, history of coronary heart disease, hypertension, diabetes, presence or not of definite spasm, use of calcium channel blocker, demonstrated that the use of aspirin plus clopidogrel is an independent risk for the primary outcome (HR 2.01, CI: 1.07–3.81, p = 0.031). The aspirin-alone group had a similar primary and individual event rate compared to the no-antiplatelet agent group (HR 0.96, CI, 0.59–1.55, p = 0.872). Smokers using aspirin plus clopidogrel had poorer outcomes than non-smokers, with HR 6.36 (CI 2.31–17.54, p = 0.045 for interaction). In conclusion, among VA patients, aspirin plus clopidogrel use is associated with a poor clinical outcome at 3 years, especially in ACS. Aspirin alone appears to be safe for use in those patients.

Vasospastic angina: A literature review of current evidence

Vasospastic angina (VSA) is a variant form of angina pectoris, in which angina occurs at rest, with transient electrocardiogram modifications and preserved exercise capacity. VSA can be involved in many clinical scenarios, such as stable angina, sudden cardiac death, acute coronary syndrome, arrhythmia or syncope. Coronary vasospasm is a heterogeneous phenomenon that can occur in patients with or without coronary atherosclerosis, can be focal or diffuse, and can affect epicardial or microvasculature coronary arteries. This disease remains underdiagnosed, and provocative tests are rarely performed. VSA diagnosis involves three considerations: classical clinical manifestations of VSA; documentation of myocardial ischaemia during spontaneous episodes; and demonstration of coronary artery spasm. The gold standard diagnostic approach uses invasive coronary angiography to directly image coronary spasm using acetylcholine, ergonovine or methylergonovine as the provocative stimulus. Lifestyle changes, avoidance of vasospastic agents and pharmacotherapy, such as calcium channel blockers, nitrates, statins, aspirin, alpha1-adrenergic receptor antagonists, rho-kinase inhibitors or nicorandil, could be proposed to patients with VSA. This review discusses the pathophysiology, clinical spectrum and management of VSA for clinicians, as well as diagnostic criteria and the provocative tests available for use by interventional cardiologists.

Pharmacotherapy of Vasospastic Angina

Vasospastic angina is a diagnosis of exclusion that manifests with signs and symptoms, which overlap with obstructive coronary artery disease, most often ST-segment elevation myocardial infarction. The pharmacotherapy that is available to treat vasospastic angina can help ameliorate angina symptoms. However, the etiology of vasospastic angina is ill-defined, making targeted pharmacotherapy difficult. Most patients receive pharmacotherapy that includes calcium channel blockers and/or long-acting nitrates. This article reviews the efficacy and safety of the pharmacotherapy used to treat vasospastic angina. High-dose calcium channel blockers possess the most evidence, with respect to decreasing angina incidence, frequency, and duration. However, not all patients respond to calcium channel blockers. Nitrates and/or alpha1-adrenergic receptor antagonists can be used in patients who respond poorly to calcium channel blockers. Albeit, evidence for use of nitrates and alpha1-adrenergic receptor antagonists in vasospastic angina is not as robust as calcium channel blockers and can exacerbate adverse effects when added to calcium channel blocker therapy. Despite having a clear benefit in patients with obstructive coronary artery disease, the benefit of beta-adrenergic receptor antagonists, statins, and aspirin remains unclear. More data are needed to elucidate whether or not these agents are beneficial or harmful to patients being treated for vasospastic angina. Overall, the use of pharmacotherapy for the treatment of vasospastic angina should be guided by patient-specific factors, such as tolerability, adverse effects, drug–drug, and drug–disease interactions.

Analytic Review: Treatment of Coronary Artery Spasm and Variant Angina

Coronary artery spasm is an abnormal constriction of the conductive arteries that produces myocardial ischemia in the absence of any marked increase in heart rate or blood pressure. Ischemia is a transient phenomenon and is promptly reversed spontaneously or by nitroglycerine. The so-called "hallmark of spasm"—ST segment elevation—is evidence for severe myocardial ischemia rather than conclusive evidence for coronary artery spasm. Any process that transiently or permanently restricts coronary blood flow (e.g., transient occlusion by thrombus) will produce similar electrocardiogram (EKG) abnormalities.

Most patients with symptoms and EKG changes related to coronary artery spasm respond to sublingual nitrates. Thus, their use for relief of the acute ischemic episode remains the initial treatment of choice. When symptoms are moderate in severity or unacceptably controlled in frequency using nitrates alone, other pharmacologic measures are needed.

When spasm is superimposed upon hemodynamically important atherosclerotic obstruction, the favorable response to calcium antagonist may not be as great as that seen when spasm occurs alone. One possible explanation is that spasm is not really occurring. The ST segment elevation may be related to transient total occlusion from platelet aggregation or thrombosis. Thus, aspirin may be the drug of choice. However, if spasm is the culprit, recommendations for surgery and angioplasty require proof that spasm is occurring in and around the area of fixed atherosclerotic obstruction and not in other vessels or over the entire course of the distal vessel.

Clinical implications of low-dose aspirin on vasospastic angina patients without significant coronary artery stenosis; a propensity score-matched analysis

BACKGROUND

High-dose aspirin has been reported to exacerbate coronary artery spasm in patients with vasospastic angina. We investigated clinical implications of low-dose aspirin on vasospastic angina patients without significant coronary artery stenosis.

METHODS

We included patients without significant coronary artery stenosis on coronary angiography (CAG) and with positive results on intracoronary ergonovine provocation test between January 2003 and December 2014. A total of 777 patients were divided into two groups according to prescription of low-dose aspirin at discharge: aspirin group (n=321) and non-aspirin group (n=456). The major adverse cardiovascular events (MACE), defined as composite outcomes of cardiac death, acute myocardial infarction, revascularization, or rehospitalization requiring CAG or medication change due to recurrent angina were compared.

RESULTS

The aspirin group had significantly higher incidence of MACE (22.8% versus 12.1%; p=0.04) and had higher tendency for rehospitalization (20.6% versus 11.2%; p=0.08). All-cause mortality and cardiac death were similar between the two groups. After propensity score matching, the aspirin group had greater risk of MACE (hazard ratio [HR] 1.54; 95% confidence interval [CI], 1.04-2.28; p=0.037) and rehospitalization requiring CAG (HR, 1.33; 95% CI, 1.13-4.20; p=0.03), and a higher tendency for rehospitalization (HR, 1.40; 95% CI, 0.94-2.09; p=0.12).

CONCLUSION

In vasospastic angina without significant coronary artery stenosis, patients taking low-dose aspirin are at higher risk of MACE, driven primarily by tendency toward rehospitalization. Low-dose aspirin might be used with caution in vasospastic angina patients without significant coronary artery stenosis.

Coronary artery spasm: Current knowledge and residual uncertainties

Myocardial ischaemia results from a direct mismatch between oxygen supply and demand, commonly arising as a result of coronary atherosclerosis, microvascular dysfunction or acute thrombosis and luminal obstruction. However, transient ischaemia may also occur due to coronary spasm leading to acute and unexpected myocardial ischaemia without obvious visible coronary pathology. Aside from symptoms of chest pain, coronary spasm can cause infarction, LV impairment, promote life threatening arrhythmias and ultimately sudden cardiac death. While therapeutic options are available, controversies exist around diagnosis, pathology, management and prognosis. This review summarises some of the common questions in this area. In particular we explore and discuss the available evidence for the pharmacological treatment of coronary spasm, and strategies for identification and management of very high risk patients to try and reduce the incidence of sudden premature death.

•

Myocardial ischaemia results from a mismatch between oxygen supply and demand.

•

Spasm might lead to myocardial ischaemia without visible coronary pathology.

•

Coronary spasm can cause infarction, LV impairment and sudden cardiac death.

Some observations on and controversies about coronary arterial spasm

The pathogenesis, clinical features, diagnosis, and treatment of spasm of epicardial coronary arteries are reviewed briefly, especially with regard to some issues that remain controversial. For diagnosis, emphasis is placed on the need for objective observations during an attack, even if that requires an attempt at pharmacologic provocation during coronary arteriography, or during echocardiography when prior arteriography has demonstrated the absence of severe coronary stenosis.

Acute coronary syndrome in a patient with multifocal coronary vasospasm

Vasospastic angina results from temporary spasm of one or more coronary segments. Although prognosis of patients presenting with coronary vasospasm appears to be generally good, multivessel coronary vasospasm may increase the risk of life-threatening cardiac events. We present a case of a 51-year-old man admitted to the emergency room due to severe retrosternal pain, who was documented with multifocal coronary vasospasm. <Learning objective: The case described illustrates the importance of recognizing coronary vasospasm as a cause of reversible ischemia. Although vasospastic angina is associated with a favorable prognosis, multivessel involvement may increase the risk of life-threatening cardiac events.>.

Persistent angina pectoris, cardiac mortality and myocardial infarction during a 12 year follow-up in 273 variant angina patients without significant fixed coronary stenosis

The incidence of cardiac events in patients with variant angina pectoris without significant coronary stenosis and ST-segment elevation was analyzed during a 12-year follow-up period in 273 consecutive patients (82% men) admitted from 1986 through 2010. Among the 252 patients who underwent electrocardiography during pain, 205 had ST-segment elevation (82%) and 45 had ST-segment depression (18%). During index hospitalization, angina occurred in 179 patients (66%), ventricular tachycardia or fibrillation in 28 (10%), and complete atrioventricular block in 3 (1%), but there were no deaths or myocardial infarctions (MIs). At 140 months, angina was still present in 129 patients (47%), but frequent angina (>10 episodes/year) occurred in only 6%. Total mortality, cardiac mortality, and MI rates were 24%, 7.0%, and 6%, respectively. Cardiac death or MI occurred in 28 patients (10%), associated with tobacco smoking (p = 0.004), antecedent "first-wind" angina (p = 0.020), and angina during hospitalization (p = 0.044) and with continued smoking (p = 0.056) and recurrent angina during follow-up (p <0.001). Multivariate analysis identified age (p = 0.001), antecedent infarction (p = 0.005), first-wind angina (p = 0.009), and smoking at index hospitalization (p = 0.027) as predictors of total mortality and treatment with calcium antagonists (p = 0.047) and smoking during follow-up (p = 0.110) for cardiac mortality and MI. In conclusion, during 12-year follow-up, patients with variant angina pectoris, mostly with ST-segment elevation during pain, had a reduced incidence of cardiac mortality and MI, associated with first-wind angina, persistent angina, and continued smoking.

[Up-date of the diagnosis and treatment of vasospastic angina]

Vasospastic or Prinzmetal's variant angina as it is also known is a special type of ischemic heart disease characterized by spontaneous episodes of chest pain accompanied by transitory ST segment elevations during the episodes. These alterations are essential for its diagnosis and it is difficult to diagnose it in their absence. If clinical suspicion is high, it should be confirmed by coronary vasospasm provocation tests, since, on the contrary, there may be cases that are not diagnosed or considered to be other types of diseases. Furthermore, progression of this type of angina to a myocardial infarction due to coronary stenosis is a relatively uncommon event.

The mystery of coronary artery spasm

Coronary artery spasm is an important cause of chest pain and myocardial ischaemia. It can be defined as an exaggerated contractile response of epicardial coronary artery smooth muscle to various stimuli but the underlying mechanism is not well understood. Recent studies have shown that the loss of endothelial vasodilatory function in conjunction with an increase in vascular smooth muscle constrictor sensitivity to calcium are the likely predisposing conditions for coronary spasm. This review highlights current understanding of the pathophysiology, predisposing factors, diagnostic and therapeutic approaches for coronary spasm.

Opioid and non-opioid analgesics

Opioids are the most potent analgesics. Toxicity results either from effects mediated by variation in affinity and intrinsic efficacy at specific opioid receptors or, rarely, from a direct toxic effect of the drugs. For some adverse effects, opioids exhibit a 'dual pharmacology' whereby these effects are usually observed only in pain-free individuals, and are not seen in patients in pain. Paracetamol, although generally very safe in therapeutic doses, displays potentially fatal toxicity in overdose requiring specific treatment. Non-steroidal anti-inflammatory drugs (NSAIDs) are known to act by inhibiting COX-1 and COX-2 isoenzymes to various degrees. Toxicity arises primarily from undesired inhibition at these enzyme sites. Knowledge of the mechanism of action of these drugs is fundamental to the understanding of their potential for toxicity, the details of which are still emerging.

Attenuation of reactive hyperemia caused by aspirin in canine coronary artery

Effects of intracoronary aspirin on coronary blood flow and reactive hyperemia were evaluated in closed-chest, anesthetized dogs. In 18 dogs the left circumflex coronary artery was cannulated and perfused by arterial blood at a constant pressure. Coronary blood flow was measured by an electromagnetic flowmeter. Intracoronary aspirin at doses of 5, 10, and 20 mg reduced coronary blood flow in a dose-dependent manner. Injection of aspirin at doses of 10 to 25 mg also inhibited reactive hyperemia following the coronary occlusion for fifteen seconds. The mean peak flow ratio was reduced from 2.13 +/- 0.42 to 1.75 +/- 0.35 (p less than 0.005). The increment of coronary blood flow provoked by intracoronary arachidonic acid at doses of 150 to 300 micrograms was almost entirely inhibited by the pretreatment of the coronary artery with aspirin. The authors conclude that aspirin increases coronary arterial resistance in a dose-dependent manner and also restricts the maximal dilating capacity, possibly by inhibition of prostacyclin synthesis.

Pathophysiology of myocardial ischemia: importance of platelet-vessel wall interactions

Clinical and experimental evidence for important interactions between platelets and vascular endothelium under conditions of myocardial ischemia is briefly summarized. The clinical evidence for a role of platelets in myocardial ischemia includes studies indicating alterations in platelet behavior and the therapeutic benefit of some antiplatelet drugs. Experimental evidence suggesting the importance of platelets in ischemia includes reductions in transmyocardial platelet number under these conditions, the cyclical reductions in coronary blood flow that result from intermittent intravascular platelet aggregation, and the relationship between induced platelet aggregation and cardiac arrhythmias. Evidence strongly suggesting the importance of platelet emboli and thromboxane generation as a major cause of reperfusion-induced ventricular arrhythmias is outlined.

Aspirin in cardiovascular disease

Although other mechanisms may be contributory, the antithrombotic properties of aspirin derive predominantly from its platelet-inhibitory effects. These are mediated via irreversible acetylation of platelet cyclo-oxygenase with subsequent blockade of platelet thromboxane synthesis. Long term administration of doses of aspirin as low as 20mg daily depresses platelet thromboxane formation by more than 90%; however, higher doses appear to be necessary to prevent thromboxane-dependent platelet activation in vivo. While there is evidence of biochemical selectivity with low doses of aspirin, significant reduction of the platelet-inhibitory eicosenoid, prostacyclin, occurs even at dosages ranging from 20 to 40mg daily. The ability of aspirin to prevent the occurrence or recurrence of vaso-occlusion has been extensively investigated. In the secondary prevention of myocardial infarction 7 placebo-controlled trials involving more than 15,000 patients have been completed. The dose of aspirin varied from 300 to 1500mg daily. Although none of the individual trials produced statistically significant reductions in total or coronary mortality, taken together the results are highly suggestive of a beneficial effect of aspirin. Similarly, 2 recent studies in patients with unstable angina demonstrated a protective effect of aspirin against acute myocardial infarction and death. While each study employed widely different doses of aspirin (324mg and 1250mg daily) similar reductions in mortality were reported. The effects of aspirin on the prevention of coronary artery bypass graft occlusion have been evaluated in 9 trials. Aspirin in doses of 100 to 975mg daily was shown to be of benefit in preventing early (less than 6 months) graft occlusion, particularly when therapy was started within 24 hours of operation. In patients with prosthetic vascular grafts of the lower limbs, aspirin has been shown to reduce platelet deposition, however further controlled trials will be required to establish the patient population most likely to benefit and, as in all these studies, the optimum dose of aspirin to employ. In patients with prosthetic heart valves it is clear that aspirin alone is insufficient to prevent thromboembolic complications and when administered as an adjunct to anticoagulant therapy it is associated with a high incidence of bleeding. In contrast, there is convincing evidence from several studies for the efficacy of aspirin in doses of 990 to 1300mg daily in the prevention of stroke and death in patients with transient ischaemic attacks.(ABSTRACT TRUNCATED AT 400 WORDS)

Platelets and antiplatelet therapy in ischemic heart disease

Blood platelets have been shown to play an important role not only in thrombosis, but also in the pathogenesis of coronary artery disease and its complications. Drugs that affect platelets have been shown to reduce mortality in survivors of acute myocardial infarction, to reduce the risk of myocardial infarction in patients with unstable angina, and to preserve the potency of saphenous venous grafts used to bypass obstructed coronary arteries. The drugs may also play a role in the primary prevention of arteriosclerosis and in preventing thrombotic complications following coronary angioplasty.

Is coronary arterial spasm part of the aspirin-induced asthma syndrome?

A 42-year-old man with aspirin-induced asthma also developed Prinzmetal's variant angina shortly after aspirin ingestion suggesting a possible physiologic relationship between bronchospasm and coronary spasm in aspirin-sensitive patients.

Effect of high dose aspirin on coronary hemodynamics during pacing-induced myocardial ischemia

The effects of aspirin on coronary hemodynamics and transcardiac concentrations of thromboxane B2 (the stable metabolite of thromboxane A2) were determined at rest and during pacing-induced myocardial ischemia in 11 patients with coronary disease. Control coronary sinus pacing increased both arterial thromboxane B2 (331 +/- 70 to 623 +/- 132 pg/ml, p less than 0.02) and coronary sinus thromboxane B2 (184 +/- 3 to 403 +/- 156 pg/ml, p less than 0.05), but positive transmyocardial gradients developed in only three patients. After 650 mg of oral aspirin, more than 90% inhibition of in vitro thromboxane B2 production was demonstrated and circulating thromboxane B2 was undetectable at rest and during pacing in all patients. Despite these changes in thromboxane B2 concentrations, coronary blood flow was unchanged by aspirin at rest (107 +/- 14 versus 112 +/- 13 ml/min, p = NS) and during pacing (189 +/- 29 versus 181 +/- 25 ml/min, p = NS). Myocardial lactate extraction was also unchanged at rest (24 +/- 7 versus 19 +/- 5%, p = NS) and during pacing (5 +/- 6 versus 9 +/- 5%, p = NS). No change occurred in the anginal threshold. Thus, aspirin does not have the vasoconstrictive properties that have been reported with another cyclo-oxygenase inhibitor, indomethacin. These findings also suggest that thromboxane A2 production does not play a major role in the pathogenesis of stress-induced ischemia. Nonetheless, intracoronary thromboxane A2 production in some patients may potentiate platelet activation and coronary thrombosis. Such patients may benefit from long-term aspirin therapy and can be treated with aspirin without risk of adverse coronary hemodynamic effects.

Large vessel coronary vasospasm: diagnosis, natural history and treatment

The diagnosis of coronary artery spasm is confirmed by angiography, for example, change in caliber of the coronary arteries plus evidence of ischemia. The prevalence and contribution of coronary artery spasm in the individual patient with symptoms of ischemic heart disease is not known and depends on how the condition is defined. The prognosis of patients with coronary artery spasm appears to depend on the presence or absence of severe coronary atherosclerosis, that is, those with severe disease have a worse prognosis. Nitrates should be used to initiate therapy in all patients with this problem. Intravenous nitrates have proven useful in patients whose symptoms are difficult to control and who require hospitalization. beta blockers used alone may be detrimental in patients with coronary artery spasm, but studies supporting the detrimental effects are few. The combination of nitrates, beta blockers and nifedipine has proved effective therapy for many patients with recurrent angina at rest, possibly related to coronary artery spasm. Several open-label and double-blind placebo control trials have shown that all of the calcium antagonists are effective short-term agents for patients with proven coronary artery spasm. When nifedipine was compared with isosorbide dinitrate in a randomized crossover, double-blind trial in patients with coronary artery spasm, both drugs were shown to be efficacious and neither was superior. The traditional alpha-blocking agents have not been shown to be an effective therapy, but a recent study of prazosin, a selective alpha blocker, revealed excellent results in patients whose conditions were resistant to therapy with traditional calcium blockers, beta blockers and, in 1 case, phenoxybenzamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary artery spasm--1984

Coronary artery spasm was virtually unknown not long ago, but the intense, ongoing interest it has generated in the past decade has produced a number of specific diagnostic techniques and therapeutic approaches, as well as considerable insight into mechanisms of coronary vascular tone and various coronary syndromes. There is growing evidence that coronary artery spasm is involved in unstable angina, stable angina, myocardial infarction, and sudden death. It is by no means a benign process and is associated with significant morbidity or mortality if misdiagnosed or untreated. It seems clear that what started as a mere clinical curiosity involving a minority of patients with the so-called Prinzmetal's variant angina is snowballing into a major arena for research, diagnosis, and treatment in the field of ischemic coronary artery disease.