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ST-Elevation Myocardial Infarction

Scenario: A 71-year-old white woman with vague complaints of dyspnea while gardening. She is presenting within 4 hours of onset of symptoms to the emergency department and has an unremarkable medical history.

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Rationale

The most common cause of ST-elevation myocardial infarction is a complete thombotic occlusion in a major coronary artery causing transmural injury. Striking ST-segment elevation is present in leads II, III, and aVF, all of which are inferior leads, suggesting that the right coronary artery is the infarct-related artery. Myocardial ischemia tends to be a regional event. When both ST-segment elevation and depression are observed on the 12-lead ECG, the ST elevation is usually considered primary and the ST depression changes are considered reciprocal. When the distal right coronary artery blood supply is inadequate, the posterior wall may become involved. Because there are no electrodes facing the posterior wall in the standard 12-lead ECG, reciprocal ST changes are represented as ST depression in leads V₂ and V₃. In addition, ST elevation is present in lead V₆, indicating apical injury.

Nursing Actions to Consider

The 1999 American Heart Association & American College of Cardiology (ACC/AHA) Guidelines for the Management of Patients With Acute Myocardial Infarction¹ recommend thrombolysis or primary percutaneous coronary intervention in patients presenting with ST elevation (greater than 0.1 mV [1 millimeter]) in 2 or more contiguous leads. In this case, the inferior wall ST segment elevation is clear and thus this patient, being younger than 75 years old, meets the guideline’s recommendation for immediate reperfusion therapy.

Continuous ST-segment monitoring is used to assess successful reperfusion, defined as 50% ST resolution in the lead showing maximal ST elevation within 90 minutes. In this case, lead III shows maximal ST elevation (10mm), and thus clinicians should expect to see fewer than 5mm in that same lead following successful reperfusion therapy. Patients with early, complete, and stable reperfusion have a favorable prognosis.

REFERENCE

1. 1999 ACC/AHA Guidelines for the Management of Patients With Acute Myocardial Infarction. A Report of the American College of Cardiology /American Heart Association Task Force on Practice Guidelines. http://www.americanheart.org/Scientific/statements/1999/AMI/edits/.

This Article Full Text (PDF) Respond to This Article Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Adams, M. G. Articles by Pelter, M. M. Search for Related Content PubMed PubMed Citation Articles by Adams, M. G. Articles by Pelter, M. M.