Study objective: To evaluate the safety and efficacy of a systematic evaluation and triage strategy including immediate resting myocardial perfusion imaging in patients presenting to the emergency department with chest pain of possible ischemic origin.
Methods: We conducted an observational study of 1,187 consecutive patients seen in the ED of an urban tertiary care hospital with the chief complaint of chest pain. Within 60 minutes of presentation, each patient was assigned to one of five levels on the basis of his or her risk of myocardial infarction (MI) or unstable angina (UA): level 1, MI; level 2, MI/UA; level 3, probable UA; level 4, possible UA; and level 5, noncardiac chest pain. In the lower risk levels (3 and 4), immediate resting myocardial perfusion imaging was used as a risk-stratification tool alone (level 4) or in combination with serial markers (level 3).
Results: Acute MI, early revascularization indicative of acute coronary syndrome, or both were consistent with risk designations: level 1: 96% MI, 56% revascularization; level 2: 13% MI, 29% revascularization; level 3: 3% MI, 17% revascularization; level 4: .7% MI; 2.5% revascularization. Sensitivity of immediate resting myocardial perfusion imaging for MI was 100% (95% confidence interval [CI], 64% to 100%) and specificity 78% (74% to 82%). In patients with abnormal imaging findings, risk for MI (7% versus 0%, P < .001; relative risk [RR], 50; 95% CI, 2.8 to 889) and for MI or revascularization (32% vs 2%, P < .001; RR, 15.5; 95% CI, 6.4 to 36) were significantly higher than in patients with normal imaging findings. During 1-year follow-up, patients with normal imaging findings (n = 338) had an event rate of 3% (revascularization) with no MI or death (combined events: negative predictive value, 97%; 95% CI, 95% to 98%). Patients with abnormal imaging findings (n = 100) had a 42% event rate (combined events: RR, 14.2; 95% CI, 6.5 to 30; P < .001), with 11% experiencing MI and 8% cardiac death.
Conclusion: This strategy is a safe, effective method for rapid triage of chest pain patients. Rapid perfusion imaging plays a key role in the risk stratification of low-risk patients, allowing discrimination of unsuspected high risk patients who require prompt admission and possible intervention from those who are truly at low risk.