Adult-Gerontology Clinical Nurse Specialist (CNS) Practice Exam

Pathologic Q waves on an ECG are most consistent with which condition?

1. Myocardial infarction

2. Premature contraction

3. Atrial fibrillation

4. Myocardial ischemia

The correct answer is: Myocardial infarction

Pathologic Q waves on an electrocardiogram (ECG) are indicative of myocardial infarction, particularly when they appear after an ischemic event that has previously resulted in necrosis of cardiac tissue. These Q waves represent a loss of electrical activity in the myocardial tissue that has been affected by the infarction, leading to a deeper and wider Q wave on the ECG. In the context of myocardial infarction, the development of pathologic Q waves usually occurs as a result of significant heart muscle damage and typically emerges several hours to days after the event. Their presence can help differentiate between different types of cardiac conditions. For instance, while myocardial ischemia may present with ST-segment changes or T wave inversions, it doesn't typically lead to the formation of abnormal Q waves unless the ischemia progresses to infarction. Other conditions such as premature contractions and atrial fibrillation do not generally lead to the development of pathologic Q waves. Instead, these conditions manifest differently on an ECG and do not indicate the same level of myocardial injury as seen in a myocardial infarction. Thus, recognizing pathologic Q waves is crucial for determining a history of myocardial infarction in the patient.