A zone of infarction produces what type of Q wave in the QRS complex?

• A. Small
• B. Normal
• C. Large
• D. Inverted

Answer: (C)

A zone of infarction results in a significant alteration in the heart muscle's electrical activity due to the loss of vascular supply, leading to necrosis or death of cardiac cells. When this occurs, the Q waves in the QRS complex can become pathologically large. These larger Q waves indicate a deep and significant loss of electrical activity in the area of the heart that has suffered an infarction.

In a normal QRS complex, Q waves may be small or even absent, but in the case of an infarct, particularly when it is transmural (affecting the full thickness of the heart wall), the Q waves can grow in depth and duration. This is often a key indicator of a prior myocardial infarction and can assist in diagnosing the extent and nature of the cardiac event during an electrocardiogram (ECG). Larger Q waves are therefore a reflection of severe damage to the myocardial tissue, making it a critical aspect of ECG interpretation.

This understanding of Q waves is essential for healthcare professionals as they assess and diagnose cardiac conditions.