What is a pathological Q wave?

As a medical professional with expertise in cardiology, I can provide you with an understanding of what a pathological Q wave is. A pathological Q wave is an abnormality observed on an electrocardiogram (ECG) that is typically indicative of a previous myocardial infarction (MI), which is commonly known as a heart attack. This occurs when there is a significant and sustained blockage in the coronary arteries, leading to a lack of oxygen and nutrients in the heart muscle. The Q wave represents the initial depolarization of the ventricles during an ECG reading. In a healthy heart, these waves are small and narrow. However, in the case of a myocardial infarction, the affected area of the heart muscle dies and is replaced by scar tissue. This scar tissue does not conduct electricity, leading to an absence of electrical activity in that region. Consequently, the ECG shows a deep and wide Q wave, which is referred to as a pathological Q wave. It is important to note that while pathological Q waves are a common finding after a heart attack, they are not pathognomonic, meaning they are not absolutely diagnostic of MI on their own. Other conditions can also cause similar changes in the ECG. Therefore, the diagnosis of a heart attack is typically made based on a combination of clinical symptoms, ECG changes, and sometimes additional testing such as cardiac enzymes or imaging studies.

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.