Myocardial Scar - ECG
The scar after a myocardial infarction develops within a few weeks after the post STEMI heart attack. The ECG identifies it as deep Q waves (greater than ¼ of the R wave in the QRS complex) in leads perpendicular to the surface of the heart, where the ischemia has occurred. Pathological Q waves develop in the late acute phase of STEMI and they are accompanied by Pardee’s waves. Deep Q may be followed by a relatively normal R wave, but frequently the R is gradually reduced to form a "QS" pattern. In the time after a STEMI infarction, the ST segment returns to the isoelectric line and the T wave may be either positive or negative. The lasting elevation of the ST segment is indicative of a ventricular aneurysm arisen as a complication of the heart attack.
Here we see an old post-infarction scar of the front wall (deep Q in V1- V4). The situation is most probably complicated by a suspected ventricular aneurysm. ST sections for QRS in V1 -V4 are elevated, best seen in V4 where the elevation reminds the Pardee’s wave (underlined in red).
Pathological Q should be located in more leads to make the scar diagnosis more likely. An isolated deep Q in lead III is normal in healthy people (more common in obese) and it is known as the "positional Q". The positional Q decreases during inspiration and in a deep inspiration it can completely disappear.
This is a very interesting ECG record. We see the old post-infarction scar with QS pattern (red). In leads II, III and aVF, however, we see clear Pardee’s waves. This is an acute STEMI of the inferior heart wall. This man has probably undergone a heart attack of the front wall in the past and now suffers from another heart attack of another heart area.