Patients with acute nontraumatic chest pain are among the most challenging patients cared for by emergency physicians. They may appear seriously ill or completely well and yet remain at significant risk for sudden death or an acute myocardial infarction (AMI).
The typical pain of myocardial ischemia has been described as retrosternal or epigastric squeezing, tightening, crushing, or pressure-like discomfort. The pain may radiate to the left shoulder, jaw, arm, or hand. In many cases, particularly in the elderly, the chief complaint is not chest pain, but of a poorly described visceral sensation with associated dyspnea, diaphoresis, nausea, light-headedness, or profound weakness. The onset of symptoms may be sudden or gradual, and symptoms usually last minutes to hours. In general, symptoms that last less than 2 min or are constant over days are less likely to be ischemic in origin. Symptoms that are new or familiar to the patient but now occur with increasing frequency, severity, or at rest are called unstable and warrant urgent evaluation even if they are absent at the time of presentation. Cardiac risk factors should be used only to predict coronary artery disease within a given population and not in an individual patient. Women, diabetics, the elderly, and patients with psychiatric disorders may have more atypical symptoms of ischemia. Although some symptoms such as radiation of pain to the arms, an exertional component, associated diaphoresis, nausea and vomiting increase the likelihood that a patient is suffering from an AMI; there is no identifiable symptom complex that allows for a definitive diagnosis of the AMI patient without objective testing.
Patients with acute myocardial ischemia may appear clinically well or be profoundly hemodynamically unstable. The degree of hemodynamic instability is dependent on the amount of myocardium at risk, associated dysrhythmias, or preexisting valvular or myocardial dysfunction. Worrisome signs may be clinically subtle, particularly the presence of sinus tachycardia, which may be due to pain and fear or may be an early sign of physiologic compensation for left ventricular failure. Patients with acute ischemia often have a paucity of significant physical findings. Rales, a third or fourth heart sound, cardiac murmurs, or rub are clinically relevant and important findings. The presence of chest wall tenderness has been demonstrated in 5% to 10% of patients with AMI, so its presence should not be used to exclude the possibility of acute myocardial ischemia. Also, response to a particular treatment such as nitroglycerin or a “gastrointestinal (GI) cocktail” should not be taken as evidence of a certain disease.
Of all the diagnostic tools clinically used in assessing chest pain, the electro-cardiogram (ECG) is the most reliable when used and interpreted correctly. Patients with acute infarctions may have ECG findings that range from acute ST-segment elevations to completely normal. This range means that the ECG is useful only when it has a positive, or diagnostic, finding. New ST-segment elevations, Q waves, bundle branch block, and ...