Noninvasive risk stratification of patients with unstable angina after clinical stabilization. Prognostic value of exercise and pharmacologic stress testing

Most of the prognostic information on patients with unstable angina is obtained hom the initial clinical assessment and the patient's subsequent course over the first few days of management. In recently stabilized patients noninvasive stress testing with exercise or pharmacologic testing provide additional useful risk assessment. Noninvasive stress testing should be part of the outpatient evaluation of low-risk patients with unstable angina and should be done within 72 hours. Unless cardiac catheterization is indicated, noninvasive stress testing should be performed in low- or intermediate-risk patients hospitalized with unstable angina who have been free of symptoms for a minimum of 48 hours. Choice of stress testing modality should be based on an evaluation of the patient's resting ECG, his or her physical ability to perform exercise, and the local expertise and technologies available. The standard ECG treadmill test should be the standard test employed in most patients with no contraindications for doing so. Provocation of ischemia at a low workload (< 5 to 6 METs) signifies a high-risk patient (cardiac mortality greater than or equal to 4%/year) who should generally merit referral to cardiac catheterization. Attainment of a higher workload (> 5 to 6 METs) without ischemia is associated with a better prognosis (cardiac mortality < 1%/year), and many such patients can be managed conservatively. Those who tolerate only a low workload but have no evident ischemia or those who develop ischemia at a high workload, represent an intermediate-risk group (cardiac mortality 2 to 3%/year) for whom several reasonable strategies can be proposed.