A deep Q wave could indicate which condition?

• A. Normal variant
• B. Atrial enlargement
• C. Necrosis and infarction
• D. Conduction block

Answer: (C)

A deep Q wave reflects myocardial necrosis from a prior infarction in the area supplied by the lead looking at that part of the heart. The Q wave is the first downward deflection of the QRS complex; when it is unusually deep and wide, it indicates that the tissue in that region has died and become electrically inert. The electrical vector shifts away from the infarcted area, producing a prominent negative deflection in the corresponding leads.

Normal small Q waves can appear in some people in certain leads, but they are typically shallow and not wide. Atrial enlargement changes the P waves, not the QRS and Q waves. Conduction block, like a bundle branch block, alters the timing and pattern of the entire QRS complex rather than creating isolated deep Q waves.