The patient with an acute coronary syndrome  presents with many symptoms and signs that reflects the degree of hypoxia and damage to the myocardium. Some 45% of patients die within 1 h of the onset of symptoms: indeed, many experience no symptoms at all and succumb from a malignant cardiac dysrhythmia such as ventricular fibrillation. Those who survive this period  present with chest pain. In unstable angina, this may be relieved by the administration of nitrate therapy and bed rest; patients with myocardial infarction have protracted pain often unrelieved
by nitrate therapy
. Such pains may radiate to the jaw and left arm. The other symptoms are explained by the severity of the insult to the myocardium and the degree of haemodynamic embarrassment that ensues. Subjects are often anxious and nauseated. This is exacerbated by the opiate analgesia often administered. Varying degrees of shock lead to low blood pressure, cutaneous vessels  vasoconstriction, and pallor; sweating as well as pump failure result in fluid congestions in the lungs. Clinical examination reveals soft heart sounds on auscultation and, where present, the signs of heart failure.