[Is a more efficient operative strategy feasible for the emergency management of the patient with acute chest pain?].

Patients with acute chest pain are a common problem and a difficult challenge for clinicians. In the United States more than 5 million patients are examined in the emergency department on a yearly basis, at a cost of 6 billion dollars. In the CHEPER registry the prevalence of patients with chest pain in the Emergency Department was 5.3%. Similarly, in 1997 at our institution the prevalence was 4.8%. Only 50% of the patients are subsequently found to have cardiac ischemia as the cause of their symptoms and 50-60% of them showed a non-diagnostic electrocardiogram (ECG). Twenty-five-50% of chest pain patients are not appropriately admitted to the hospital and despite this conservative approach, acute myocardial infarction is misdiagnosed up to 8% of patients with acute chest pain who are released from the emergency department without further evaluation, accounting for approximately 20% of emergency department malpractice in the United States. Important diagnostic information is covered by the patient's medical history, physical examination, and ECG, but often this approach is inadequate for a definitive diagnosis. Creatine kinase (CK) and CK isoenzyme--cardiac muscle subunit (CK-MB)--are traditionally obtained in the emergency department in patients admitted for suspected acute coronary syndrome. Mass measurements of CK-MB have improved sensitivity and specificity, and to date this is the gold standard test for diagnosis of acute myocardial infarction. CK-MB, however, is not a perfect marker because it is not totally cardiac specific and does not identify patients with unstable angina and minimal myocardial damage. There are no controlled clinical impact trials showing that these tests are effective in deciding whether to discharge or to appropriately admit the patient with suspected acute coronary syndrome. Relevant investigative interest has recently been focused on new markers for myocardial injury, including myoglobin, cardiac troponins T and I. Myoglobin, a sensitive but not specific marker for cardiac damage, increases earlier than CK-MB and cardiac troponins. It should be used early after symptom onset and in conjunction with a more specific marker of myocardial damage. Cardiac troponins T and I are highly specific markers for cardiac damage, rise parallel to CK-MB and remain elevated longer, up to 5 to 9 days. They are useful for detection of less severe degrees of myocardial injury, which may occur in several patients with unstable angina who are at higher risk of cardiac events. Recent studies suggest that cardiac troponins have good diagnostic performance and prognostic value in the heterogeneous population of patients seen in the Emergency Department with acute chest pain. Despite these promising data, several analytical and interpretative problems in the routine use of cardiac troponins must be solved. Incremental value of echocardiography in acute chest pain patients is still uncertain. Echocardiography can be recommended as an adjunctive test if readily available during acute chest pain or prolonged pain, especially in patients without previous myocardial infarction. Rest myocardial radionuclide imaging has been studied in the emergency department setting and although the overall diagnostic performance and prognostic value of sestamibi has been found to be promising, it is not suitable, in our country, for extensive clinical use. ECG exercise stress test in the emergency department population has been shown to be safe and it has a good negative predictive value for cardiac events. It should be recommended that any institution identify specific and shared protocol and strategies for management of patients with chest pain. These should include basal clinical evaluation, serial ECG and the use of specific and sensitive myocardial markers. Adjunctive tests, such as echocardiography, nuclear studies and stress tests should be employed when indicated taking into account local facilities.