How to diagnose ST-Elevation Myocardial Infarction (STEMI) in an electrocardiogram (EKG) with atrial pacing?

From the Guidelines

Diagnosing STEMI in an atrial paced ECG requires careful assessment of specific criteria, including concordant ST-segment elevation of ≥1 mm in leads with a positive QRS complex or ST-segment depression of ≥1 mm in leads V1-V3 with a negative QRS complex, as recommended by the 2017 ESC guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation 1.

Key Considerations

• The Sgarbossa criteria, originally developed for LBBB, can be applied to paced rhythms with modifications, including discordant ST-segment elevation of ≥5 mm in leads with a negative QRS complex, which is highly suggestive of STEMI.
• When evaluating a suspected STEMI in a paced rhythm, it is essential to compare with previous ECGs if available, and consider the clinical context including symptoms, cardiac biomarkers, and hemodynamic status.
• The 2017 ESC guidelines emphasize the importance of initiating ECG monitoring as soon as possible in all patients with suspected STEMI to detect life-threatening arrhythmias and allow prompt defibrillation if indicated 1.

Diagnostic Approach

• In patients with a clinical suspicion of myocardial ischemia and ST-segment elevation, reperfusion therapy needs to be initiated as soon as possible, according to the 2017 ESC guidelines 1.
• If the ECG is equivocal or does not show evidence to support the clinical suspicion of MI, ECGs should be repeated and, when possible, compared with previous recordings.
• In cases of uncertainty, urgent cardiac catheterization or advanced imaging like echocardiography may be necessary to confirm the diagnosis, as paced rhythms can mask ischemic changes.

Clinical Context

• A high index of suspicion is warranted in patients with typical symptoms even if ECG criteria aren't fully met, as the 2017 ESC guidelines recommend considering the clinical context, including symptoms, cardiac biomarkers, and hemodynamic status, in the diagnosis of STEMI 1.
• The guidelines also emphasize the importance of a regional reperfusion strategy to maximize efficiency in the management of STEMI 1.

From the Research

Diagnosing STEMI in Atrial Paced EKG

To diagnose STEMI in an atrial paced EKG, consider the following points:

• STEMI diagnosis is primarily based on clinical presentation and EKG findings, regardless of the pacing mode 2, 3.
• In atrial paced EKG, the pacing spikes may interfere with the interpretation of the ST segment, making it challenging to diagnose STEMI.
• Look for signs of myocardial ischemia or infarction, such as:
  • ST-segment elevation or depression
  • Q-waves or pathological Q-waves
  • T-wave inversion or peaking
  • New left bundle branch block (LBBB)
• Consider the clinical context, including symptoms such as chest pain, shortness of breath, or fatigue, and risk factors for coronary artery disease.
• If STEMI is suspected, prompt activation of the catheterization laboratory for primary percutaneous coronary intervention (PPCI) is crucial, regardless of the pacing mode 2.
• The timing of heparin administration may not significantly impact the thrombolysis in myocardial infarction (TIMI) flow grade in patients with STEMI treated with PPCI 3.