The absence of the ST-segment elevation in acute coronary artery thrombosis: what does not fit, the patient or the explanation?

In a few patients with acute proximal thrombotic occlusion of the left anterior descending coronary artery (LAD), tall ischemic T waves never evolve into ST-segment elevation. This was recently inaccurately reported as a “novel sign” of proximal LAD occlusion. It has been speculated that the absence of ST-segment elevation could be attributed to the large area of transmural ischemia, the anatomic variant of Purkinje fibers, or to lack of activation of sarcolemal adenosine triphosphate–potassium channels. This electrocardiographic picture was recently explained by changes in the subendocardial but not in the epicardial action potential, suggesting subendocardial ischemia as the underlying mechanism. We present a patient with thrombotic lesion of proximal LAD, static precordial ST-segment depression, and tall T waves who underwent primary percutaneous intervention and stent placement. Surprisingly, total thrombotic stent occlusion on the following day was associated with ST-segment elevation in precordial leads, indeed supporting the concept of the regional subendocardial ischemia that was first described more than a decade ago.