When is thrombolytic therapy indicated in the treatment of myocardial infarction (MI)?

Updated: Dec 31, 2017
  • Author: Wanda L Rivera-Bou, MD, FAAEM, FACEP; Chief Editor: Erik D Schraga, MD  more...
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Thrombolytic therapy is indicated in patients with evidence of ST-segment elevation MI (STEMI) or presumably new left bundle-branch block (LBBB) presenting within 12 hours of the onset of symptoms if there are no contraindications to fibrinolysis.

STEMI is defined as new ST elevation at the J point in at least two contiguous leads of 2 mm (0.2 mV) or more in men or 1.5 mm (0.15 mV) in women in leads V2-V3 and/or 1 mm (0.1 mV) or more in other contiguous limb leads. [14]

STEMI equivalents, such as isolated posterior-wall MI, present with ST depression in twoor more precordial leads (V1-V4). In left main coronary artery occlusion, Electrocardiography (ECG) reveals multilead ST depression in at least six leads with coexistent ST elevation in lead aVR. [15, 16]

New or presumably new LBBB at presentation occurs infrequently and should not be considered diagnostic of acute MI (AMI) in isolation unless it is clinically unstable. [15, 17] The Sgarbossa criteria are the most validated tool to aid in the diagnosis of STEMI in the presence of LBBB. [18] A meta-analysis [19] found a 98% specificity for the concordance criteria and a positive predicted value for AMI.

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