Focused Follow-Up Visit: Resting 12-Lead ECG An ECG is necessary when there is a change in anginal pattern, symptoms or findings suggestive of a dysrhythmia or conduction abnormality, and near or frank syncope. It is important to recognize that periodic recording of the standard 12-lead ECG has clinical value that is independent of diag- nostic and prognostic content: It provides a baseline wave- form against which tracings taken during symptoms reason- ably can be compared. Because many patients with SIHD have resting repolarization abnormalities, absence of a timely tracing for comparison with a tracing taken during atypical symptoms can lead to overdiagnosis of acute ische- mia.1233,1234 Conversely, repolarization abnormalities dur- ing symptoms that might be new or significantly more marked can also be consistent with old disease and lead to underdiagnosis or undertreatment of unstable disease.1235 New repolarization abnormalities during serial study have been shown to predict cardiovascular events during the longitudinal study of hypertensive patients in the Framing- ham Heart Study.318 A study of hypertensive patients that included a subgroup with established SIHD also demon- strated an increased risk of cardiovascular endpoints after the development of new repolarization changes during serial evaluation.318,1236 Although there are no prospective randomized data demonstrating that intervention based on routine, periodic evaluation of the ECG alone will alter outcomes in patients with SIHD, pending such evidence, the clinical value of a change in the resting ECG is widely accepted. In patients with established SIHD, a change in a periodically obtained ECG can be the only evidence of intercurrent silent infarction, inadequately treated hyper- tension, or complex arrhythmia that would modify treat- ment. 