Chest Pain

Chapter 21 Chest Pain

Chest pain is a very common symptom, and its severity and etiology will depend, to a large extent, on the clinical circumstances in which it occurs. Chest pain is the most frequent new symptom reported by patients seen in outpatient clinics. Although it is an extremely nonspecific symptom (Box 21-1), it may be the presenting manifestation of a number of conditions, most of which will be relatively benign. Also, in many patients with such pain, a firm diagnosis may never be established. When chest pain is a presenting symptom in the emergency department setting, however, more serious, acute, and potentially life-threatening causes need to be considered. Accordingly, a complaint of chest pain requires thorough and careful investigation.

Box 21-1

Causes of Chest Pain

Differential Diagnosis

The pathophysiology of chest pain is understood for many but not all of the conditions with which it is associated. The most common form of chest pain is musculoskeletal pain. The causes of this form of chest pain are legion—in some instances involving an organic process, often due just to excessive coughing, as discussed later on. Of note, however, possible psychiatric or psychogenic reasons for chest pain need to be kept in mind. Cardiac disease is the most important cause of chest pain overall, so this entity is first in the overview of potential causes.

Myocardial Ischemia

The chest pain associated with myocardial ischemia is attributed to an imbalance between myocardial oxygen (O2) supply and demand. Most tissues can increase O2 supply by increasing O2 delivery, increasing O2 extraction, or both. O2 extraction by the myocardium is much greater than that occurring in other tissues, manifested by the O2 content of coronary venous blood normally being much lower than that of blood coming from other muscles. Because the ability of the myocardium to increase O2 extraction is limited, the primary mechanism by which the heart increases O2 delivery in response to increased demands is to increase coronary blood flow.

Coronary blood flow is determined by the driving pressure (i.e., the aortic pressure minus the left ventricular end-diastolic pressure) and the resistance in the coronary arteries. Chest pain can therefore be caused by conditions that increase myocardial O2 demand (e.g., hypertension, hyperthyroidism, exercise) in the setting of a limited ability to increase O2 supply, decrease mean aortic pressure (e.g., aortic stenosis), decrease O2 delivery (e.g., anemia, hypoxemia), or increase the downstream pressure for coronary arterial flow (e.g., aortic and mitral valve disease, left or right ventricular hypertrophy, or dilatation). The importance of coronary arterial diameter is apparent in Poiseuille’s law, which states that resistance is inversely related to the vessel radius taken to the fourth power, explaining why anything that might result in even a small change in coronary arterial diameter (e.g., coronary arterial spasm, thrombosis, atherosclerosis) can result in chest pain.

A wide range of disorders other than angina may be the cause of chest pain. These potential alternative diagnoses are summarized in Box 21-2.

Jun 12, 2016 | Posted by in RESPIRATORY | Comments Off on Chest Pain

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