Once you've stabilized a patient with chest pain, having gone through the ABCs (airway, breathing and circulation), then it's reasonable to proceed to the diagnostic work-up. First, make sure that you have intravenous access and the patient is on a monitor. An electrocardiogram (ECG) should be done first, along with a rapid history and physical examination. I'd be looking for signs of heart failure and would consider a chest x-ray as part of my diagnostic work-up. If the chest pain is ischemic in origin, consider a trial of nitrates -- provided the patient hasn't been exposed to sildenafil (Viagra) in the last 48 hours. Viagra causes a fall in systolic blood pressure of 10 mm Hg and up to 30-40 mm Hg in patients on nitrates. Treat chest pain with morphine and give oxygen as needed. The ECG is extremely important for a diagnosis of ischemic heart disease. If the patient has evidence of a new bundle branch block or S-T elevation, consider thrombolysis. Patients with normal ECGs have a low event rate, so more time is available for the diagnostic work-up. Patients with S-T depression, however, have a roughly 10% chance of dying or having a myocardial infarction (MI) within three months. The second important tool is using myocardial markers to look for evidence of ischemia or damage. Traditionally, creatine kinases (CKs) along with the myocardial (MB) fraction are measured every eight hours for the first 24 hours. These tests have a proven track record but, unfortunately, in the first six to 12 hours they may turn out negative. On the other hand, earlier markers such as myoglobin (probably the best clinical early marker) are very nonspecific -- a swift kick in the shin can cause myoglobins to be elevated. Troponins are supposed to be very specific for the heart and can pick up so-called micronecrosis -- evidence of ischemia with normal CKs. They also remain elevated for up to a week and can be useful to determine if someone has had an MI a number of days ago. Our hospital has switched to measuring troponins in place of MB fraction. Troponin levels certainly add specificity and sensitivity to your cardiac work-up, but they aren't always right. In the first six to eight hours, they're no better than the MB fraction. Most physicians have seen a number of patients, such as those with renal failure, whose troponins show an increase unrelated to cardiac pathology. The bottom line, however, is that your clinical assessment and judgement are the most important factors. GC