ANGINA PECTORIS



Angina pectoris is chest discomfort caused by transient myocardial ischemia without necrosis, usually resulting from the inability of athero­sclerotic arteries to increase myocardial blood flow under conditions of increased demand. Coronary spasm may occur either alone or in the presence of fixed coronary obstruction and reduces flow without an increase in demand. Angina pectoris is considered stable when there exists a chronic course of predictable exertional chest pain and unstable if a change in chronic angina consisting of increased frequency, duration, or severity oc­curs. The onset of new angina, or angina occurring at rest or with minimal exertion, or angina awak­ening the patient from sleep is considered un­stable. Unstable angina pectoris has also been termed preinfarction angina, crescendo angina, acute coronary insufficiency, and intermediate coronary syndrome and usually requires hospital admission to exclude an acute myocardial infarc­tion.

The patient’s history is crucial in the diagnosis of angina pectoris . Even if coro­nary artery disease is known to exist anatomi­cally, e.g., by arteriography, the functional sig­nificance of these lesions must be assessed from the patient’s history of chest pain. The pattern of precipitation by exertion and disappearance with rest is one of the most characteristic features of angina pectoris. The pain or discomfort is often located in the left precordium or midchest di­rectly under the sternum. It is sometimes not con­sidered pain by the patient but described as pres­sure, burning, tightness, or fullness; the classic gesture is a clenched fist over the chest. The pain may appear over the period of a few seconds or minutes and disappears gradually in the same manner. It is usually not sharp or knifelike and does not occur suddenly at full intensity or leave abruptly. It lasts between one-half minute and ap­proximately 20 minutes. Ischemic pain that lasts longer suggests myocardial necrosis. Typical an­gina is relieved with nitroglycerin or rest over a period of 30 seconds to several minutes. Imme­diate relief (within a few seconds), incomplete re­lief, or relief 20 to 30 minutes after sublingual ni­troglycerin is not typical of angina pectoris. The pain may radiate to the neck, jaw, epigastrium, shoulder, and the arms, most frequently the left arm. Pain localized to the left inframammary area is less characteristic. Chest wall tenderness is usu­ally not present. Common precipitating factors are brisk walking, climbing stairs, using the hands above the head (for example, shaving, hair comb­ing), emotional upset, exposure to cold, and a large meal. Redistribution of intravascular vol­ume at night may cause angina decubitus, that is, angina occurring with the supine position. Exis­tence of precipitating causes such as anemia, thy­rotoxicosis, infection, aortic stenosis, arrhyth­mias, and hypertension should be excluded. Weakness, dyspnea, nausea, pallor, and diapho­resis may occur with the pain. Many patients mis­interpret the sensation as “gas,” and belching is not uncommon.
Findings on physical examination are nonspe­cific. An S4 gallop is often present but may only be heard during an episode of acute ischemia (de­creased diastolic compliance with ischemia). Likewise, a murmur of papillary muscle dysfunc­tion may occur only with ischemia. When my­ocardial ischemia is not present at rest, exercise tests may unmask ECG evidence of ischemia (see Stress Testing in Chapter 2). Thallium perfusion scintigraphy or exercise radionuclide ventricu­lography increases the sensitivity and specificity of exercise testing, particularly in patients with abnormal baseline electrocardiograms because of digitalis, pre-existing nonspecific ST-T wave changes, or left bundle branch block. Exercise echocardiography has become practical with two-dimensional echo techniques and may reveal regional wall motion abnormality during or im­mediately after exercise. In addition to its diag­nostic role, the treadmill exercise test is important to assess the functional capacity and prognosis of patients with known coronary artery disease.
If the patient presents with pain of unknown origin, exercise testing may be useful diagnos-tically, but only after rest and medication have relieved the pain and an acute myocardial infarc­tion has been excluded. Patients with rest pain or particularly severe anginal syndromes should not undergo exercise testing but instead should pro­ceed directly to coronary angiography after sta­bilization. Patients who present with unstable an­gina have a higher percentage of left main and severe three vessel disease than patients with chronic, stable angina.
The natural history of stable angina pectoris is variable, and several years may pass in some pa­tients without the development of unstable angina or myocardial infarction. The most important fac­tors to judge prognosis are measures of left ven­tricular function, the number of vessels contain­ing significantly stenotic lesions, and exercise tolerance. Patients with significant left main cor­onary artery stenoses have a poor prognosis and are considered for surgery on the basis of their anatomy alone.
The indications for coronary angiography are relatively narrow (see Table 2-19). For patients in whom the differentiation of coronary artery dis­ease from noncoronary causes of chest pain can­not be made despite a careful history and non­invasive evaluation, coronary arteriography may be the only means to exclude or establish the di­agnosis of coronary artery disease. In addition, for patients in whom coronary artery spasm is sus­pected, the administration of ergonovine at car­diac catheterization may exclude or confirm that diagnosis. When ischemic pain is refractory to medical management, surgery very effectively eliminates pain (Table 7-2). Because specific subgroups of patients may demonstrate increased survival from coronary bypass surgery, some phy­sicians recommend coronary angiography for any patient with known or suspected coronary artery disease in order to exclude left main or certain subsets of three-vessel coronary artery disease. Since this practice subjects many patients to the risk (albeit small) of coronary angiography, most physicians select patients for coronary angiogra­phy from subgroups at particularly high risk for having left main or three-vessel coronary artery disease, for example, patients with recurrent chest pain after myocardial infarction (especially sub­endocardial myocardial infarction), patients with poor exercise performance (positive test in first two stages or 6 minutes of exercise), and patients presenting with an unstable pattern of angina pec­toris. Using these high-risk subgroups as a guide to selecting patients for catheterization, few pa­tients with left main coronary artery stenosis would be missed. Many physicians also cathe-terize any young patient (below age 40) who pre­sents with significant angina or myocardial in­farction and any patient resuscitated from cardiac arrest. The ability of coronary artery bypass sur­gery to prolong life in many other subgroups of patients with coronary artery disease, particularly those patients with mild or moderate degrees of angina, is unproven.
Some patients, especially diabetics, may have “silent” ischemia, that is, episodes of ischemia,well-documented by ECG, imaging, or echo tech­niques unassociated with chest discomfort. This lack of an anginal “warning system” may result from autonomic nervous system abnormalities and may be dangerous, since severe ischemia can occur without the patient’s realizing that he needs to stop his activity. Some patients may manifest symptoms of ischemia as dyspnea rather than chest discomfort (angina-equivalent dyspnea).