Acute coronary syndrome (defined here as unstable angina and non-ST elevation myocardial infarction [MI]) is characterized by episodes of chest pain at rest or with minimal exertion that are increasing in frequency or severity, often with dynamic electrocardiography (ECG) changes. Show
We do not know whether intravenous nitrates, beta blockers, or calcium channel blockers reduce the risk of MI or death, although they may reduce the frequency and severity of chest pain. CAUTION: Short-acting dihydropyridine calcium channel blockers may increase mortality in persons with congenital heart disease. Early, routine cardiac catheterization and revascularization may reduce death and nonfatal MI compared with conservative strategies (medical treatment with or without subsequent cardiac catheterization and revascularization). DefinitionAcute coronary syndrome encompasses unstable angina, non-ST elevation MI (new term for non-Q wave MI, often referred to as non-STEMI), and ST elevation MI (new term for Q wave MI, often referred to as STEMI). Unstable angina and non-STEMI are overlapping entities and will be discussed together in this review. STEMI is not discussed in this review. Unstable angina with non-STEMI is a spectrum of disease that involves an imbalance of supply and demand of oxygen available to the myocardium. This causes symptoms such as new-onset exertional angina, preexisting angina that is refractory to nitroglycerin, or angina at rest. The pathophysiology governing anginal symptoms is usually caused by atherosclerotic plaque that nearly obstructs coronary vessels. The distinguishing feature between unstable angina and non-STEMI is the presence of elevated cardiac markers, such as troponin, which implies myocardial damage. Patient history alone is insufficient to make a diagnosis of acute coronary syndrome. The clinical dilemma of distinguishing between cardiac and noncardiac pain requires a combination of patient history, ECG, and biomarkers. Overlapping clinical entities in the acute coronary syndrome spectrum of disease allow for similar treatment strategies, and many trials include persons with either unstable angina or non-STEMI. We have included systematic reviews and randomized controlled trials in a mixed population of persons with unstable angina, non-STEMI, or both, which we will refer to here as acute coronary syndrome. IncidenceIn the United States, acute coronary syndrome accounts for more than 1.4 million hospital admissions per year. In industrialized countries, the annual incidence of unstable angina is about six out of 10,000 persons in the general population. Etiology and Risk FactorsRisk factors are the same as for other manifestations of ischemic heart disease—older age, previous atheromatous cardiovascular disease, diabetes, smoking, hypertension, hypercholesterolemia, male sex, and a family history of premature ischemic heart disease. It can also occur in association with other disorders of circulation, including valvular disease, arrhythmias, and cardiomyopathies. PrognosisBetween 9 and 19 percent of persons with acute coronary syndrome die in the first six months after diagnosis, with about one half of these deaths occurring within 30 days of diagnosis. Several risk factors may indicate poor prognosis and include severity of presentation (e.g., duration of pain, speed of progression, evidence of heart failure); medical history (e.g., previous acute coronary syndrome, acute MI, left ventricular dysfunction), other clinical parameters (e.g., age, diabetes), ECG changes (e.g., severity of ST segment depression and deep T wave inversion), biomarkers (e.g., presence of troponin concentration elevation), and change in clinical status (e.g., recurrent chest pain, silent ischemia, hemodynamic instability). However, several key prognostic indicators associated with adverse outcomes may be used to aid clinical decision making. Variables, including age 65 years or older, at least three risk factors for coronary artery disease, known significant coronary stenosis, degree of ST segment deviation, recurrent anginal symptoms in 24 hours, use of aspirin in past seven days, and elevated cardiac biomarkers, can be used to generate a scoring system to identify high-risk patients who may experience true ischemic cardiac events and death (thrombolysis in MI risk score). The more of these factors that are present, the greater the likelihood of adverse ischemic events. This helps stratify patients according to risk and identify high-risk patients. What is the difference between unstable angina and heart attack?With a heart attack, lack of blood flow causes the heart's muscle cells to start to die. With unstable angina, the blood flow is not completely blocked by the blood clot. But the blood clot can quickly grow and block the artery.
What is the difference between angina and MI?Sometimes these plaques grow slowly, and sometimes the plaque tears or ruptures, and a blood clot forms, acutely narrowing the artery partially (angina) or completely (heart attack or myocardial infarction).
What separates unstable angina from myocardial infarction?Unstable angina and NSTEMI are differentiated one from the other primarily by their severity—whether the ischemia is prolonged enough to lead to structural myocardial damage and to the release of detectable markers of myocardial injury, most commonly troponin I (TnI), troponin T (TnT), or creatine kinase (CK)-MB. Fig.
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