Myocardial infarction redefined: Impact on case-load and outcome of patients with suspected acute coronary syndrome and nondiagnostic ECG at presentation Alberto Conti a, * , Filippo Pieralli a , Lucia Sammicheli a , David Antoniucci b , Riccarda Del Bene b , Giuseppe Barletta b a Emergency Medicine Department, Chest Pain Unit, Azienda Ospedaliero, Universitaria Careggi, Florence, Italy b Department of the Heart and Vessels, Azienda Ospedaliero, Universitaria Careggi, Florence, Italy Received 26 March 2005; received in revised form 8 June 2005; accepted 18 June 2005 Available online 8 August 2005 Abstract Risk stratification of chest pain (CP) is still debated. Objective of this study was to evaluate the performance of a risk stratification model for patients with suspected acute coronary syndrome (ACS) and nondiagnostic ECG at presentation, in whom the occurrence of myocardial infarction was either diagnosed following traditional (t-MI) or the recently redefined (r-MI) criteria. First-line 6-h work-up categorized 3068 patients with suspected ACS and nondiagnostic ECG into low-risk for short-term coronary events, intermediate-risk who entered second-line work-up, and high-risk. Intermediate-risk patients with positive second-line work-up and high-risk patients were considered for urgent coronary angiography. Angina, non-fatal MI, sudden death, and revascularization constituted composite end-point (CE) for in-hospital and 6-month outcome. ACS incidence was 16%; r-MI increased by 62% the diagnosis of MI over t-MI. Among 2024 discharged low-risk patients, 12 (0.6%) had non-fatal CE at 6 months. ACS was diagnosed in 19% of 503 intermediate-risk and 96% of 389 high-risk patients. Among ACS patients, in- hospital CE occurred in 14% of t-MI, 7% of r-MI, and 9% of unstable angina (UA) patients (t-MI vs. r-MI and t-MI vs. UA: p < 0.05, for both); 6-month CE occurred in 23%, 16% and 12% of t-MI, r-MI and UA, respectively (t-MI vs. UA: p <005). Sensitivity, specificity and accuracy were high both for diagnostic (97%, 98%, 99%, respectively) and treatment (83%, 98%, 97%, respectively) strategy. Risk stratification, and categorization according to traditional or redefined MI and UA criteria allow safe allocation of resources in CP patients with suspected ACS and nondiagnostic ECG at presentation because outcome is accurately predicted. D 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Chest pain; Acute coronary syndrome; Myocardial infarction 1. Introduction Sensitivity for acute myocardial infarction (AMI) under classical criteria of ECG highly suggestive of AMI or ischemia is reported to be 79% in patients arriving at the Emergency Department with chest pain (CP) [1]. While a fast-track system is advised in which pharmacological or mechanical revascularization is established in patients with persistent ST-segment elevation [2], in patients with ST- segment depression, adjunctive risk stratification by deter- mination of serum markers of myocardial injury is needed [3–5]. In this context, patients with elevated serum levels of troponins are recognized to have better outcome when managed by early invasive approach as compared with patients without abnormal level of troponins [6]. Patients with acute CP and nondiagnostic ECG are considered at low-risk of subsequent coronary events, and risk stratifica- tion by troponin determination or stress-imaging are needed to improve diagnosis of ACS and guide subsequent 0167-5273/$ - see front matter D 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2005.06.034 * Corresponding author. Emergency Medicine, Careggi General Hospital, Viale Morgagni, 85, 50134 Firenze, Italy. Tel.: +39 055 4277748; fax: +39 055 4277247. E-mail address: aaaconti@hotmail.com (A. Conti). International Journal of Cardiology 111 (2006) 195 – 201 www.elsevier.com/locate/ijcard