Evolving MI

1. Normal QRS/T configuration. Note the normal, asymetrical nature of the T. It has a gentle upstroke and a more rapid down stroke.
   
   
2. In the first few minutes to hours before a transmural MI, the patient can develop "Hyperacute Ts". This is indicated by large symetrical T waves in representitive leads.
   
   
3. As the deprived tissue becomes injured, one can observe classic ST elevation (also called current of injury). Note the upward convexity (or downward concavity) of the ST Segment. Again, this occurs in the first hours of an MI. The greater the injury, the greater the ST elevation.
   
   
4. If quick intervention fails to open the blocked coronary artery, tissue will start to infarct or necrose (die) and cause Q wave development. Note the inversion of the T waves indicating that this MI has been in progress for hours.
   
   
5. If the patient survives but has lost that myocardial wall, a significant Q wave will form with a diminishing of R wave amplitude. This significant Q wave indicates infarcted/necrotic myocardial tissue. This is Days to weeks later.
   
   
6. As collaterals develop over time, the ischemia will decrease and T waves will normalize. (weeks to months).

Rarely, the ST segment can remain elevated weeks to months after an MI. This persistent ST segment elevation beyond several days can indicate the ventricle wall has developed an aneurysm.