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Treatment Because myocardial damage progresses rapidly during the early hours, efforts during this critical period must be directed toward reducing myocardial oxygen demand and improving coronary blood supply to diminish the extent of myocardial damage. To be maximally effective, these interventions must be initiated as soon as possible: The reduction in benefit is very time-dependent, and patients who are treated within an hour fare significantly better than those treated later. Thus, prompt reperfusion therapy via primary angioplasty or thrombolytic therapy should be initiated in the absence of contraindications as early as possible in patients with ST elevation acute infarctions. It is now becoming clear that urgent treatment also reduces the morbidity associated with non-Q wave infarctions as well, especially if followed by definitive intervention on the infarct related artery. A. EMERGENCY CARE AND PROTOCOLS More than 85% of patients who present with ST elevation within 4 h of the...

Clinical Findings The clinical presentations of patients with AMI vary. Although most patients have had chest discomfort prior to the onset of infarction, 20% or more have infarction as a first manifestation of ischemic heart disease; in 20–30% of patients, infarction may go unrecognized. Nonetheless, symptoms are generally present. A. SYMPTOMS AND SIGNS The most common and best symptom on which to base a consideration of MI is chest discomfort, usually described as “pressure,” “dull,” “squeezing,” “aching,” or “oppressive,” although it may be described differently because of individual variability, differences in articulation or verbal abilities, or concomitant disease processes. The discomfort is usually in the center of the chest and may radiate to the left arm or the neck. In general, patients with ischemic chest pain tend to be still, but patients with infarction can be restless as well. The nature of the pain may lead patients to place a hand over the sternum (Levine’s sign)...

It is generally accepted that a prolonged imbalance between myocardial oxygen supply and demand leads to the death of myocardial tissue. Coronary atherosclerosis is an essential part of the process in most patients. Ischemic heart disease seems to progress through a process of plaque rupture that transiently increases the amount of luminal impingement by the stenotic lesion. Infarction may occur when the plaque ruptures and leads to thrombosis, erosion of the plaque causes thrombosis, or when cardiac work exceeds the ability of the narrowed coronary artery to supply nutritive perfusion. Recent work suggests that inflammation may play a pivotal role in the genesis of plaque rupture. Greater numbers of acute infarctions occur during the early morning hours (from 6:00 AM to 12:00 noon) than any other time of the day, suggesting that perhaps the increased catecholamine secretion associated with awakening or circadian changes in coagulation common in the early morning (eg, increases in type...

A. GENERAL APPROACH Because myocardial ischemia is produced by an imbalance between myocardial oxygen supply and demand, in general, treatment consists of increasing supply or reducing demand—or both. Heart rate is a major determinant of myocardial oxygen demand, and attention to its control is imperative. Any treatment that accelerates heart rate is generally not going to be efficacious in preventing myocardial ischemia. Therefore, care must be taken with potent vasodilator drugs, which may lower blood pressure and induce reflex tachycardia. Furthermore, because most coronary blood flow occurs during diastole, the longer the diastole, the greater the coronary blood flow; and the faster the heart rate, the shorter the diastole. Blood pressure is another important factor: Increases in blood pressure raise myocardial oxygen demand by elevating left ventricular wall tension, and blood pressure is the driving pressure for coronary perfusion. A critical blood pressure is required that does ...

General Considerations For clinical purposes, patients with chronic ischemic heart disease fall into two general categories: those with symptoms related to the disease, and those who are asymptomatic. Although the latter are probably more common than the former, physicians typically see symptomatic patients more frequently. The issue of asymptomatic patients becomes important clinically when physicians are faced with estimating the risk to a particular patient who is undergoing some stressful intervention, such as major noncardiac surgery. Another issue is the patient with known coronary artery disease who is currently asymptomatic. Such individuals, especially if they have objective evidence of myocardial ischemia, are known to have a higher incidence of future cardiovascular morbidity and mortality. There is, understandably, a strong temptation to treat such patients, despite the fact that it is difficult to make an asymptomatic patient feel better, and some of the treatment modaliti...