PURPOSE: The 12-lead ECG in the emergency department is at the hub of the therapeutic decision pathway because ST-segment elevation identifies patients who most benefit from reperfusion therapy. The optimal definition of ST elevation for diagnosis of anterior wall ST elevation myocardial infarction (STEMI), with respect to the measuring point or the amplitude is unknown. METHODS: One hundred six consecutive patients with acute myocardial infarction who visited our emergency medical center from August 2005 to June 2007 were prospectively recruited. Patients with atrial flutter/fibrillation, bundle brach block, left ventricular hypertrophy, preexcitation, ventricular aneurysm, or paced rhythm were excluded. ST segment was measured at the J point, 40 ms after the J point, 80 ms after the J point, and relative to the PR segment, in all six precordial leads. The diagnostic accuracy of ST segment measuring point and amplitude were assessed by receiver operating characteristic (ROC) curve analysis. RESULTS: Mean ST segment amplitude in all precordial leads was lowest when measured at the J point, and highest when measured at 80 ms after the J point. ST segment measured at 40 ms after the J point had the highest predictive value for diagnosing anterior STEMI (p=0.01). The optimal cutoff value for precordial leads ST segment amplitude was greater than 2 mm in leads V2, and V3 and greater than 1 mm in other precordial leads. Using these cutoff values, leads V2-V4 were more accurate than the other precordial leads. With, sensitivities of 82%, 90%, and 82%, respectively, and specificities of 80%, 85%, and 78%. The areas under the ROC curve for leads V2-V4 were 0.90 (95% CI: 0.83-0.96), 0.93 (95% CI: 0.88-0.98), and 0.88 (95% CI: 0.82-0.94). CONCLUSION: Different measurements of the ST segment result in variations in the sensitivity and specificity of diagnosis of anterior STEMI. This new criteria for ST segment elevation is crucial for identifying patients eligible for emergency reperfusion therapy.
Aneurysm ; Diagnosis ; Electrocardiography* ; Emergencies ; Emergency Service, Hospital ; Humans ; Hypertrophy, Left Ventricular ; Myocardial Infarction* ; Prospective Studies ; Reperfusion ; ROC Curve ; Sensitivity and Specificity