Pathophysiology of acute myocardial infarction

More than 80% of acute myocardial infarcts are the result of coronary atherosclerosis with superimposed luminal thrombus. Uncommon causes of myocardial infarction include coronary spasm, coronary embolism, and thrombosis in nonatherosclerotic normal vessels. Additionally, concentric subendocardial necrosis may result from global ischemia and reperfusion in cases of prolonged cardiac arrest with resuscitation. Myocardial ischemia shares features with other types of myocyte necrosis, such as that caused by inflammation, but specific changes result from myocyte hypoxia that vary based on length of occlusion of the vessel, duration between occlusion and reperfusion, and presence of collateral circulation.     

Update on acute coronary syndromes and ST-elevation myocardial infarction

PURPOSE: The goal of modern therapy of acute myocardial infarction is twofold: to achieve rapid reperfusion of ischemic myocardium and to decrease subsequent remodeling, which can have deleterious effects on ventricular function and prognosis. The current paradigm for treatment of most patients with acute coronary syndromes is the consideration of an 'early invasive' strategy. RECENT FINDINGS: Studies published this year have reinforced the importance of early reperfusion, solidified the evidence for early institution of aggressive adjunctive treatment, and added newer therapies to the existing armamentarium. This review evaluates published data from the past year encompassing advancements in percutaneous coronary intervention, drug-eluting stents, glycoprotein IIb/IIIa antagonists, thienopyridines, HMG-CoA reductase inhibitors, aldosterone blockade, low-molecular-weight heparins, direct thrombin inhibitors, implantable cardioverter-defibrillators, and beta-blockade in the treatment of acute coronary syndrome and ST-segment elevation myocardial infarction. In addition to patency of the epicardial coronary arteries, the role of the microvascular has become an area of recent interest. SUMMARY: As novel modalities and approaches are put to the test of clinical trials, evidence-based therapies may help to lessen the adverse effects of myocardial ischemia and reduce future cardiovascular events.     

Pathophysiology of cardiogenic shock complicating acute myocardial infarction

Cardiogenic shock is a rapidly progressive, often fatal complication of acute myocardial infarction. A vicious circle of ischemia, decreased cardiac output and reinfarction progress to left ventricular failure and death. The fundamental pathophysiology of this cascade and other mechanisms beyond the classic paradigm of ischemia and dysfunction are discussed in detail.     

心肌桥致急性前壁心肌梗死的临床风险分析

目的探讨心肌桥致急性前壁心肌梗死的特征及临床风险。方法统计因急性胸痛疑心肌梗死行造影检查检出心肌桥的30例患者以及因急性胸痛造影检查无心肌桥的30例患者,分析心肌桥与急性前壁心肌梗死的关系,以及心肌桥致急性心肌梗死的特点。结果两组患者性别、年龄、高血压、高脂血症、家族史、吸烟史方面比较差异均无统计学意义。心肌桥患者在胸闷和胸痛方面无特异表现。在硝酸甘油疗效方面,30例心肌桥患者中3例(10.0%)有疗效;而无心肌桥患者11例(36.7%)有疗效。另外,30例心肌桥患者25例(83.3%)心功能在Ⅲ级或者Ⅳ级,而无心肌桥患者18例(60.0%)心功能在Ⅲ级或者Ⅳ级;心肌桥患者最终16例(53.3%)发生心肌梗死,而无心肌桥患者有8例(26.7%)发生心肌梗死。结论心肌桥患者服用硝酸甘油疗效很差,心肌梗死的风险有所提高,应早期防治。     

Abciximab and atherosclerotic heart disease: use in percutaneous coronary intervention,acute coronary syndromes and acute myocardial infarction

Abciximab irreversibly binds to the glycoprotein IIb/IIIa receptor on both activated and unactivated platelets inhibiting platelet aggregation. It has been studied in a variety of clinical settings including percutaneous coronary intervention (PCI), ST-elevation myocardial infarction, and non ST-elevation acute coronary syndromes. Abciximab has been demonstrated to reduce acute ischaemic events in the setting of percutaneous intervention with both percutaneous transluminal coronary angioplasy and stenting. It has been shown to be particularly effective when used in patients with acute myocardial infarction undergoing primary PCI. The data for its effective use in the medical phase of therapy for patients with acute coronary syndromes, however, is not as consistent. In this article we review the major trials evaluating the use of abciximab in these clinical scenarios compared with placebo and alternative glycoprotein IIb/IIIa inhibitors.     

Critical decision making in the management of patients with acute myocardial infarction and other acute coronary syndromes

The decision-making process for emergency physicians in managing patients with signs or symptoms of AMI or unstable angina is quite different than that used by other specialists who might evaluate such patients in a less critical setting (e.g., a cardiologist seeing a private patient in an office or outpatient clinic environment). The emergency physician's evaluation must be highly focused and follow established principles of emergency medicine (Fig. 2). Although the evaluation and treatment of all patients must be individualized to some degree, increasing experience at high-volume centers nationally indicates that well-constructed institutional strategies, protocols, and critical pathways can help emergency physicians to provide consistent, cost-effective management of such patients.     

Amphetamine-related acute myocardial infarction due to coronary artery spasm

A 27-year-old man developed acute myocardial infarction after intravenous amphetamine use. A coronary angiogram showed plaques in the mid-portion of the left anterior descending artery which developed coronary artery spasm after administration of intracoronary ergonovine. The findings in this case suggest that these coronary artery plaques played a role in the endothelial dysfunction resulting from amphetamine use, and that induction of coronary arterial spasm was the likely mechanism of amphetamine-related acute myocardial infarction.     

Exercise tolerance as a predictor of acute myocardial infarction in emergency department patients with potential acute coronary syndromes

There is mounting evidence that exercise tolerance is an important predictor of heart disease. Our objective was to determine if decreased exercise tolerance, as estimated by physicians, may be useful in stratifying risk in Emergency Department (ED) patients with potential acute coronary syndromes. We conducted a prospective cohort study on a convenience sample of ED patients at an urban teaching hospital. Patients with chest pain, dyspnea, syncope, or epigastric pain who were evaluated for acute coronary syndromes were included. Clinical and laboratory data were recorded. In addition, the Emergency Physicians were asked to estimate the exercise tolerance of the patient as excellent, good, bad, or very poor. The primary outcome of the study was myocardial infarction (MI) or death in patients stratified by physician-perceived exercise tolerance (excellent or good vs. bad or very poor). There were 166 patients enrolled in the study. Nine patients (5%) had an MI; there were no deaths. Physicians reported exercise tolerance as excellent in 33 patients, good in 63, bad in 50, and very poor in 20. The unadjusted risk of MI was significantly elevated in patients with physician-perceived decreased exercise tolerance (relative risk = 4.8, 95% confidence interval 1.03-22). After adjustment for age, sex, and major cardiovascular risk factors, decreased exercise tolerance remained a significant predictor of MI (adjusted odds ratio = 7.3, 95% confidence interval 1.2-46). Exercise tolerance, as estimated by clinical impression, may be an important predictor of complications in ED patients presenting with potential acute coronary syndromes.     

Acute coronary syndromes: unstable angina/non-ST elevation myocardial infarction

Acute coronary syndrome is a major health problem affecting approximately 1.5 million individuals a year. Early diagnosis and appropriate evidence-based therapies improve clinical outcomes significantly. Current data suggest that an early invasive therapy may improve intermediate-term and long-term outcomes, particularly in high-risk individuals. The last few years also have seen significant advances in antiplatelet and antithrombotic therapies for the management of patients who have acute coronary syndrome.     

Primary percutaneous coronary intervention in acute myocardial infarction

Primary percutaneous coronary intervention (PCI) has emerged as the preferred therapy for acute ST-segment elevation myocardial infarction (STEMI), as multiple randomized clinical trials and pooled analyses have shown improved clinical outcomes compared with medical reperfusion. Unfortunately, medical centers with 24-hour PCI capability are concentrated in urban areas, relegating many patients in the United States to inferior medical reperfusion. Ongoing substantial research efforts are directed at optimizing mechanical reperfusion, including refinements in adjuvant medical therapy and the use of drug-eluting stents in the catheterization laboratory. Research efforts are also focusing on the implementation of streamlined transfer systems from community centers to tertiary care centers, akin to systems used in the trauma model. Furthermore, experience with the performance of primary PCI at community centers without onsite surgical backup is growing. This article summarizes data regarding the current state, challenges, and future directions of primary PCI for STEMI, emphasizing adherence to current American College of Cardiology/American Heart Association guidelines.     

Pathophysiology of acute coronary syndrome

This article reviews the current understanding of the pathophysiology of acute coronary syndrome and how these concepts have altered our clinical approach to the acute phase of coronary heart disease. Thrombosis due to erosion or, in most cases, rupture of a vulnerable atherosclerotic plaque underlies most acute coronary syndromes. The protective fibrous cap undergoes degradative processes controlled by inflammatory mediators that break down the interstitial collagen within the fibrous cap. Thrombus formation depends on factors in the solid-phase of the ruptured plaque as well as on fluid-phase determinants in blood. Depending on the degree of thrombus formation the subsequent obstruction of the coronary artery is followed clinically by unstable angina, non-ST- and ST-segment elevation myocardial infarction.     

MRI demonstration of acute myocardial infarction due to posttraumatic coronary artery dissection

A case of left ventricular lateral wall myocardial infarction in the distribution of circumflex coronary artery (LCX) was demonstrated by magnetic resonance imaging in a 55-year-old woman. Dissection of the proximal LCX due to blunt chest trauma was followed by percutaneous coronary artery stenting. MR (magnetic resonance) imaging of myocardial infarction is reviewed.     

急性心肌梗死冠状动脉介入治疗疗效探讨

目的比较经股动脉与桡动脉两种途径冠状动脉介入治疗（PCI）急性心肌梗死的疗效。方法将广东医学院第三附属医院收治的120例心肌梗死患者按照动脉穿刺途径分为桡动脉组60例和股动脉组60例,对两组间的动脉穿刺点压迫时间、PCI的成功率、穿刺点局部并发症、下肢静脉血栓及低血压、尿潴留的发生率进行对比分析。结果股动脉组成功率为93.33%,桡动脉组成功率为95.00%。两组PCI的成功率、下肢静脉血栓比较差异无统计学意义（P〉0.05）;穿刺点压迫时间、穿刺点局部的并发症、低血压及尿潴留的发生率,桡动脉组与股动脉组比较,桡动脉显著少于股动脉组,差异有统计学意义（P〈0.05）。结论经桡动脉与股动脉途径行经皮冠状动脉介入治疗急性心肌梗死成功率相似,但经桡动脉途径行经皮冠状动脉介入治疗急性心肌梗死血管并发症少,有利于有效安全的抗凝治疗,值得临床推广。     

Pathophysiology, prognostic significance and clinical utility of B-type natriuretic peptide in acute coronary syndromes

The natriuretic hormones are a family of vasoactive peptides that can be measured circulating in the blood. Because they serve as markers of hemodynamic stress, the major focus of the use of natriuretic peptide levels [predominantly B-type natriuretic peptide (BNP) and N-terminal (NT)-pro-BNP] has been as an aid to the clinical diagnosis and management of congestive heart failure (CHF). Recently, however, the measurement of natriuretic peptides in the acute coronary syndromes (ACS) has been shown to provide information complementary to traditional biomarkers (of necrosis) such as cardiac troponins and creatine kinase (CK). Studies in several types of acute coronary syndromes [ST-segment elevation myocardial infarction (STEMI), non-ST elevation MI (NSTEMI) and unstable angina (UA)] have shown that elevated levels of natriuretic peptides are independently associated with adverse outcomes, particularly mortality. Additional information is obtained from the use natriuretic peptides in combination with other markers of risk including biomarkers of necrosis and inflammation. This review will summarize the scientific rationale and clinical evidence supporting measurement of natriuretic peptides for risk stratification in acute coronary syndromes. Future research is needed to identify therapies of particular benefit for patients with ACS and natriuretic peptide elevation.     

急性心肌梗死后延迟冠状动脉介入术的临床分析

目的　探讨急性心肌梗死(AMI)后延迟经皮冠状动脉腔内成形术及支架术治疗的临床疗效。方法　将88例患者分为经皮冠状动脉介入治疗(PCI)和非PCI组,PCI组于发病后平均13d行PCI术。随访两组患者的心脏事件发生率。结果　与非PCI组相比,PCI组患者在不稳定型心绞痛发作,左室射血分数的提高及复合终点事件方面差异有显著性。结论　AMI后延迟PCI可减少患者的心脏事件发生。     

急性心肌梗死的延迟性经皮冠状动脉介入治疗的疗效探讨

目的通过对急性心肌梗死(acutemyocardialinfarction,AMI)急性期后行延迟性经皮冠状动脉介入治疗(percutaneouscoronaryintervention,PCI),观察其疗效,安全性和预后。方法53例AMI患者,入院后按AMI诊断和治疗指南犤1犦作常规治疗(包括溶栓治疗),在发病5～15d后为患者作PCL结果共干预梗死相关动脉(infarctrelatedarteries,IRA)68支68处病变,经皮腔内冠状动脉成形术,(percutaneoustransluminalcoronaryangioplastyPTCA)加支架64例,直接植入支架4例,共植入支架68枚。术前IRA前向血流心肌梗死溶栓治疗试验(thrombolysisinmyocardialinfarctiontrial,TIMI)分级0～2级,术后均达到TIMI3级。住院期间无一例死亡、再发心肌梗死、梗塞后心绞痛、再次血管重建。出院后随访5～48个月,再发心肌梗死1例(1.9%),死亡1例(术后5个月,1.9%)不稳定型心绞痛3例(6～14个月,5.7%)。再次PCI2例,冠状动脉旁路移植术(coronaryarterybypassgraft,CABG)1例,再次血管重建率5.7%。术后6～48个月无死亡。再次住院7人次(13.2%)。结论急性期后延迟性PCI能明显改善AMI患者的近期和远期预后,提高生活质量。且相对安全,操作风险少。