Nonspecific ST-T changes (usually defined as ST devia- tion of <0.5 mm [0.05 mV] or T-wave inversion of <2 mm [0.2 mV]) are less helpful diagnostically. Significant Q waves Table 4. Summary of Recommendations for Prognosis: Early Risk Stratification Recommendations COR LOE References Perform rapid determination of likelihood of ACS, including a 12-lead ECG within 10 min of arrival at an emergency facility, in patients whose symptoms suggest ACS I C 21 Perform serial ECGs at 15- to 30-min intervals during the first hour in symptomatic patients with initial nondiagnostic ECG I C N/A Measure cardiac troponin (cTnI or cTnT) in all patients with symptoms consistent with ACS* I A 21, 64, 67 71 Measure serial cardiac troponin I or T at presentation and 3 6 h after symptom onset* in all patients with symptoms consistent with ACS Use risk scores to assess prognosis in patients with NSTE-ACS I A 42 44, 75 80 Risk-stratification models can be useful in management IIa B 42 44, 75 81 Obtain supplemental electrocardiographic leads V7 in patients with initial nondiagnostic ECG at intermediate/high risk for ACS IIa B 82 84 Continuous monitoring with 12-lead ECG may be a reasonable alternative with initial nondiagnostic ECG in patients at intermediate/high risk for ACS BNP or NT pro-BNP may be considered to assess risk in patients with suspected ACS IIb B 87 91 *See Section 3.4, Class I, #3 recommendation if time of symptom onset is unclear. ACS indicates acute coronary syndromes; BNP, B-type natriuretic peptide; COR, Class of Recommendation; cTnI, cardiac troponin I; cTnT, cardiac troponin T; ECG, electrocardiogram; LOE, Level of Evidence; N/A, not available; NSTE-ACS, non ST-elevation acute coronary syndromes; and NT pro-BNP, N-terminal pro- B-type natriuretic peptide. Figure 2. 