If the initial ECG is not diagnostic but the patient remains symptomatic and there is a high clinical sus- picion for ACS, serial ECGs (eg, 15- to 30-minute in- tervals during the first hour) should be performed to detect ischemic changes. (Level of Evidence: C) 3. Serial cardiac troponin I or T levels (when a con- temporary assay is used) should be obtained at pre- sentation and 3 to 6 hours after symptom onset (see Section 3.4, Class I, #3 recommendation if time of symptom onset is unclear) in all patients who pres- ent with symptoms consistent with ACS to identify a rising and/or falling pattern of values.21,64,67 71 (Level of Evidence: A) 4. Additional troponin levels should be obtained beyond 6 hours after symptom onset (see Section 3.4, Class I, #3 recommendation if time of symptom onset is un- clear) in patients with normal troponin levels on seri- al examination when changes on ECG and/or clinical presentation confer an intermediate or high index of suspicion for ACS.21,72 74 (Level of Evidence: A) 5. Risk scores should be used to assess prognosis in pa- tients with NSTE-ACS.42 44,75 80 (Level of Evidence: A) Class IIa 1. Risk-stratification models can be useful in manage- (Level of Evidence: B) 2. It is reasonable to obtain supplemental electrocardio- graphic leads V7 in patients whose initial ECG is nondiagnostic and who are at intermediate/high risk of ACS.82 84 (Level of Evidence: B) Class IIb 1. Continuous monitoring with 12-lead ECG may be a reasonable alternative in patients whose initial ECG is nondiagnostic and who are at intermediate/high risk of ACS.85,86 (Level of Evidence: B) 2. 