ST-segment elevation is the clinical hallmark of ST-elevation myocardial infarction; however pathophysiologically ST elevation occurs in association with acute coronary occlusion long before any myocardial necrosis occurs, for example. with no myocardial infarction (MI). The clinical utility of these laboratory observations has previously been limited; however, with the advent of permanently implantable high-fidelity electrocardiogram monitors, such utility constitutes a new horizon for high-risk patients. Rapidly progressive changes in the endocardial electrogram, with real-time alarms, could shift the timing, and hence the paradigm of care from interruption of MI to prevention of MI.