Further observations on the deep Q 3 of the electrocardiogram

Abstract

Working on the theory that a Q wave in Lead III produced by infarction is due to a Q wave in V F, the author has drawn the following tentative conclusions: 1. 1. The disappearance of Q 3 on deep inspiration is probably proof that it is positional, although failure to disappear is not incontrovertible proof of a coronary origin. 2. 2. The voltage of Q 2 is a fairly good index of the depth of the Q wave in V F, but this is not absolutely dependable. 3. 3. A significantly deep Q 3 may be less than 25 per cent as large as the largest R wave. 4. 4. W-shaped QRS complexes in Lead III may contain a deep Q 3. 5. 5. R 3 need not be present. 6. 6. A small, initial, upward deflection apparently takes the Q 3 out of the coronary class. 7. 7. A deep Q 3 that is due to infarction is relatively rare.