What is the management approach for a patient with a prolonged ST segment on an electrocardiogram (ECG)?

Management of Prolonged ST Segment on ECG

A prolonged ST segment on ECG requires prompt evaluation for acute coronary syndrome, with immediate coronary angiography and reperfusion therapy indicated for patients with clinical signs of ongoing myocardial ischemia, especially when accompanied by ST-segment elevation or depression. 1

Initial Assessment and Interpretation

• ST-segment elevation ≥0.1 mV in two contiguous leads (≥0.2 mV in V1-V3) suggests acute coronary occlusion requiring immediate reperfusion therapy 1
• ST-segment depression ≥0.05 mV in leads V1-V3 may represent posterior myocardial infarction and should be treated as STEMI 1
• Additional posterior leads (V7-V9) should be used to detect ST elevation in suspected posterior MI 1
• ST-depression >0.1 mV in eight or more surface leads with ST elevation in aVR/V1 suggests left main or multivessel coronary obstruction 1

Management Algorithm for Prolonged ST Segment

1. For ST-Segment Elevation or New/Presumed New LBBB:

• Immediate reperfusion therapy is indicated 1
• Preferred approach: Emergency coronary angiography with primary PCI 1
• If PCI unavailable: Intravenous thrombolysis within 30 minutes of arrival 1

2. For ST-Segment Depression or T-Wave Changes:

• Administer aspirin 75-150mg, clopidogrel, LMWH or unfractionated heparin, beta-blocker, and nitrates 1
• Perform serial troponin measurements (at presentation and 6-12 hours later) 1
• If high-risk features present (positive troponin, recurrent symptoms): Proceed to coronary angiography 1

3. For Atypical ECG Presentations with Ongoing Ischemic Symptoms:

• Immediate coronary angiography is indicated despite absence of classic ST-segment elevation 1
• This includes patients with:
  • Left bundle branch block (especially with concordant ST elevation) 1
  • Ventricular paced rhythm 1
  • Isolated posterior MI 1
  • ST elevation in lead aVR 1

Special Considerations

Bundle Branch Block

• In LBBB, look for concordant ST elevation (in leads with positive QRS) as indicator of MI 1
• RBBB usually doesn't hamper interpretation of ST elevation but indicates poor prognosis 1
• Point-of-care troponin 1-2 hours after symptom onset may help decide on emergency angiography 1

Ventricular Paced Rhythm

• Consider reprogramming pacemaker to evaluate intrinsic rhythm if patient is not pacemaker-dependent 1
• Urgent angiography may be required to confirm diagnosis 1

Non-Diagnostic Initial ECG

• Repeat ECG or continuous ST-segment monitoring is crucial 1
• Look for hyperacute T waves, which may precede ST elevation 1
• Persistent ischemic symptoms despite medical therapy warrant emergency angiography even without diagnostic ST changes 1

Monitoring and Additional Diagnostic Tools

• ECG monitoring should be continued for at least 24 hours or until alternative diagnosis is made 1
• Two-dimensional echocardiography can help identify regional wall motion abnormalities that occur within minutes of coronary occlusion 1
• Serial troponin measurements are essential for diagnosis of myocardial infarction 1

Common Pitfalls to Avoid

• Misinterpreting ST elevation in conditions like left ventricular aneurysm, pericarditis, or benign early repolarization 2, 3
• Failing to recognize atypical presentations of STEMI, such as isolated posterior MI 1
• Delaying reperfusion therapy in patients with new or presumed new LBBB and clinical suspicion of MI 1
• Not considering multivessel or left main disease in patients with widespread ST depression and ST elevation in aVR 1
• Overlooking the need for additional posterior leads (V7-V9) in suspected posterior MI 1