A 65-year-old man presents to the Emergency Department with severe anterior chest pain lasting one hour. He reports having experienced infrequent mild stable angina over the past two years:

• Sinus rhythm, 60/min
• Left axis deviation
• Left anterior fascicular block
• Acute anterior infarction

Notice the tall, broad T waves in the anterior leads: these are hyperacute T waves. They may be transiently seen in the early stage of an acute myocardial infarction. 

There is also an elevation in the J point, which is where the QRS ends and the ST segment begins:

The patient was given thrombolytic therapy, resulting in transient improvement. However, four hours later his chest pain returned:

• Sinus rhythm, 64/min
• Acute anterior infarction

The patient was brought to the cath lab, where he was found to have severe stenoses in the proximal-mid left anterior descending artery, which was successfully dilated and stented. The patient once again became pain-free and hemodynamically stable. The following ECG was recorded four hours post-catherterization: 

• Marked sinus bradycardia, 49/min
• Compared with the previous tracing, the ST elevation is much less marked, and the T waves are deeply negative in the anterolateral leads
• Evolutionary changes of acute anterior infarction