STEMI Equivalents: Opportunities to Save Myocardium
1TBD, Baystate Medical Center, United States of America
Several important acute coronary syndromes that require emergent intervention present with well-defined changes on the electrocardiogram. Most posterior wall infarcts occur as an extension of an inferior MI. Rarely, just the posterior wall may infarct, usually due to occlusion of the circumflex artery. The signs of isolated posterior MI include ST-segment depression in V1-3 and then development of R waves in V1-2 (the equivalent of Q waves). Patients with this finding should be referred emergently for intervention, either cath or thrombolysis. ST-segment depression in ≥ 8 leads AND ST-segment elevation in aVR is associated with critical stenosis of the left main coronary artery. These patients need urgent catheterization and possible CABG. Critical stenosis of the proximal LAD artery is associated with either biphasic or inverted T waves in V2-3 occurring in the pain free interval following a significant episode of chest pain. In their original paper, Wellens described this finding in 18% of patients admitted for unstable angina and found 75% of these patients went on to have an anterior MI within weeks. These patients need aggressive medical management and urgent cardiac catheterization. DeWinters, et al, has described persistent precordial hyperacute T waves associated with upsloping ST-segment depression representing occlusion of the proximal LAD. This pattern was noted in 2% of anterior MIs. This pattern should be referred for immediate intervention.
Lawner BJ, Nable JV, Mattu A. Novel patterns of ischemia and STEMI equivalents. Cardiol Clin 30:591-599, 2012.
Verouden NJ, deWinter RJ, et al. Persistent precordial ”hyperacute” T-waves signify proximal LAD occlusion. Am Heart J 95:1701-1706, 2009.