Activate or Wait – 006

62 year-old woman with two hours of central crushing chest pain. Smoker, hypertension.

ETA 30 minutes.

Would you activate your cath lab/STEMI protocol?

A second ECG was performed en route:

Activate or wait ECG 2354 02 LITFL

ECG interpretation

Lateral STEMI

  • ST elevation and hyperacute T waves (HATW) laterally in leads V2-6
  • Q-waves in aVL, V1-V4
  • Have a close look at the T wave in V2-3 in in the initial ECG — these authors consider these to be HATW. Remember, the area under the curve is more important than the height in HATW, which often present initially as wide, bulky T waves.

Note the evolution of changes between the first and second ECGs. ST segments have elevated further in lateral leads, and Q-waves in V1-V3 have deepened and extended to V4 and aVL, indicating progressive ischaemia in this territory.


Key Finding:

Occlusion of mid left circumflex artery


  • Left Main Coronary Artery – mild irregularities.
  • Left Anterior Descending Coronary Artery – mild irregularities.
  • Left Circumflex Coronary Artery – large calibre vessel. Non-dominant. 99% stenosis in mid vessel. culprit.
  • Right Coronary Artery – large calibre vessel. dominant. Mild irregularities.


Single vessel coronary artery disease. 99% stenosis left circumflex. Successful percutaneous coronary intervention to mid left circumflex with drug eluting stent

1. Dual antiplatelet therapy for 12 months. Lifelong aspirin.
2. Ongoing cardiovascular risk factor management.
3. Smoking cessation.
5. Admit CCU.

Clinical Pearls
  • There is no formal definition/criteria for hyperacute T waves (HATW). Pay close attention to the area under the curve, as HATW often present initially as wide, bulky T waves


Further reading

Online resources


EKG Interpretation

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

MBBS (Hons), BMSci (Hons). Cardiology Registrar at Royal Perth Hospital in Perth, Australia. Graduate of The University of Western Australia in 2016 with Honours and completed Basic Physician Training with the RACP in 2021. Passion lie in cardiac imaging and electrophysiology.

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