Less than half of patients with a chest pain history indicative of acute coronary syndrome have a diagnostic electrocardiogram (ECG) on initial presentation to the emergency department. The physician must dissect the ECG for elusive, but perilous, characteristics that are often missed by machine analysis. ST depression is interpreted and often suggestive of ischemia; however, when exclusive to leads V1-V3 with concomitant tall R waves and upright T waves, a posterior infarction should first and foremost be suspected. Likewise, diffuse ST depression with elevation in aVR should raise concern for left main- or triple-vessel disease and, as with the aforementioned, these ECG findings are grounds for acute reperfusion therapy. Even in isolation, certain electrocardiographic findings can suggest danger. Such is true of the lone T-wave inversion in aVL, known to precede an inferior myocardial infarction. Similarly, something as ordinary as an upright and tall T wave or a biphasic T wave can be the only marker of ischemia. ECG abnormalities, however subtle, should give pause and merit careful inspection since misinterpretation occurs in 20-40% of misdiagnosed myocardial infarctions.