Analysis of acute coronary ischemia–time insensitive predictive instrument (ACI-TIPI) as a clinical prediction rule in emergency department chest pain protocol patients undergoing stress testing

Abstract

Study objectives: This study is designed to determine if the Acute Coronary Ischemia–Time Insensitive Predictive Instrument (ACI-TIPI) score can identify chest pain protocol patients for whom stress testing can be avoided without increasing the number of adverse cardiac events occurring within 30 days after chest pain center evaluation. Methods: This is a prospective, observational cohort study of low- to intermediate-risk chest pain center patients for whom acute myocardial ischemia (AMI) has been excluded and provocative cardiac testing obtained. An ACI-TIPI score was assigned on arrival to the chest pain center, the results of which were blinded to the treating physician. Subsequently admitted patients underwent medical record review for death, AMI, unstable angina, cardiac interventions, and final diagnosis. All patients received a telephone call at 30 days, medical records review, and social security death index review for follow-up. Institutional review board approval was obtained with waiver of informed consent. Results: One thousand seven hundred fifty-one consecutive patients with low to intermediate risk were evaluated from June 1, 2000, through March 22, 2001, with our chest pain protocol in the chest pain center. One thousand four hundred seventy-eight patients underwent stress testing and ACI-TIPI score assignment. Of the study group, 400 patients had an ACI-TIPI score below 20; 4 of these patients were found to have an acute coronary syndrome, which leads to a miss rate of 0.01 and a negative predictive value of 0.99. In the study cohort, 265 patients had an ACI-TIPI score below 20 and were men younger than 35 and women younger than 45 years. For men younger than 35 and women younger than 45 years of age and with an ACI-TIPI score below 20, the observed cardiac event rate was zero, resulting in a negative predictive value of 100%. Conclusion: The use of the ACI-TIPI score could be applied to further risk stratify patients safely following a chest pain protocol that rules out AMI. If all male patients younger than 35 years and all female patients younger than 45 years in whom AMI was excluded and the ACI-TIPI score was less than 20 had been sent home, 217 (15%) stress tests would have been safely avoided, with no observed adverse cardiac events.