As a medical professional with expertise in cardiology, I can tell you that a significant Q wave on an electrocardiogram (ECG) is often an indication of prior myocardial infarction, also known as a heart attack. This occurs because the Q wave represents the initial depolarization of the ventricles during a heartbeat. When a portion of the heart muscle dies due to lack of blood supply, as in a heart attack, that area is replaced by scar tissue which does not conduct electricity. This absence of electrical activity in the scarred region can lead to the appearance of a pathologic Q wave on an ECG. In summary, a significant Q wave is typically a sign that a part of the heart has been damaged and replaced by non-electrically active scar tissue, which is a consequence of a previous myocardial infarction. read more >>

A pathologic Q wave. Pathologic Q waves are a sign of previous myocardial infarction. They are the result of absence of electrical activity. A myocardial infarction can be thought of as an elecrical 'hole' as scar tissue is electrically dead and therefore results in pathologic Q waves.read more >>