Routine admission of patients with chest pain in an attempt to rule out acute myocardial infarction results in more than two million hospital admissions each year. Ultimately, as few as one third of these patients have actually had an acute coronary event. Because the rate of actual coronary events appears to be so low, alternative strategies have been developed to better identify which patients truly require admission. Increasingly, patients are identified as low risk based on their symptoms, coronary risk factors, and results of physical examination and electrocardiogram (ECG). Immediate exercise treadmill testing (IETT) also has been shown to be a safe and effective means of identifying a coronary event in low-risk patients. Lewis and associates extend their previous work in this study by evaluating the safety and efficacy of IETT in low-risk patients with known coronary artery disease who present to the emergency department with chest pain.
All patients with known coronary artery disease who presented to an emergency department for chest pain over a five-year period were eligible for the study. Initial examination included a history and physical examination, bilateral blood pressure measurements, chest radiograph, 12-lead ECG and, in most cases, baseline serum cardiac enzyme measurements. Based on these results, patients considered to be low risk were identified and included in the study. IETT using a modified Bruce protocol and with an emergency department physician present was initiated as soon as possible following the initial examination. Acute myocardial infarction (AMI) was diagnosed based on the results of serial ECGs or abnormal results of cardiac enzyme testing.
A total of 100 patients were enrolled in the study, with 23 patients considered positive for a coronary event, 38 patients negative, and 39 patients nondiagnostic. No complications of IETT were recorded during or after testing. Of the 23 patients in the positive group, two had non-Q wave AMI. Thirty-three patients in the negative group were discharged immediately after testing, and five were admitted for eight-hour observation. Of the 39 patients in the nondiagnostic group, 22 were discharged immediately after the test, 11 were admitted for eight-hour observation and six underwent further cardiac evaluation. No AMIs were found in either of the latter groups. Eighty patients were available for follow-up at six months, and none of them had an adverse coronary event during that time.
The authors conclude that IETT is a safe, effective means of screening for coronary events in low-risk patients who present with chest pain and known coronary artery disease. Use of IETT helps to stratify patients who need admission for further evaluation and those who can be discharged. Of note is that the authors recommend baseline evaluation of cardiac enzymes testing to rule out non-Q wave AMI.