When a “Normal” ECG Hides an Acute Myocardial Infarction – Recognizing Hyperacute T Waves

A previously healthy man in his 40s presented with severe chest pain radiating to both arms. The pain occurred at rest and was partially positional and respiration-dependent.

Initial Assessment

The ECG on admission was interpreted as essentially normal. Given his young age and the absence of clear ST changes, a coronary event was considered less likely.

Hyperacute T-waves in V5 and V6. Early signs of ischemia

Further Evaluation

Echocardiography showed posterolateral hypokinesis, prompting urgent angiography.Coronary angiography revealed an occluded circumflex marginal branch (CX), successfully treated with PCI.

Occlusion of Cx-artery

Flow in CX-artery after wire-crossing

ECG Interpretation – Was It Really Normal?

On closer examination, the ECG showed:

• Hyperacute T waves in V5–V6

• Decreased amplitude post-PCI → ischemia in viable myocardium

• T-wave inversions in V5–V6 → reperfusion in the lateral wall

• Tall T waves in V1–V2 → reperfusion in the posterior wall

Hyperacute T waves are often the earliest sign of ischemia. ST elevation may appear later – or not at all.

T-waves in V5 and V6 have become smaller - ischemia is resolved

T-wave inversion in V5 and V6 (reperfusjon of lateral wall) anf highIlarge T-waves in V1 and V2 (reperfusjon of the posterior wall)

📚 Key Learning Points

1️⃣ An ECG may look normal despite serious ischemia – always assess T-wave morphology.2️⃣ Hyperacute T waves are an early STEMI-equivalent pattern.3️⃣ Around 50% of CX occlusions do not meet STEMI criteria.4️⃣ Reperfusion signs: lateral T-wave inversion (V5–V6) and tall T waves in V1–V2.

💡 Take-home Message

A “normal” ECG does not rule out acute coronary disease.Recognizing hyperacute T waves early can be life-saving.

🔑 Keywords

ECG interpretation, hyperacute T waves, myocardial infarction, STEMI equivalent, circumflex occlusion, cardiology education, medical blog