These are the most positive deflections when the lead axis and QRS axis are parallel (or most negative if the current flows toward the negative electrode).

These are the most positive deflections when the lead axis and QRS axis are parallel (or most negative if the current flows toward the negative electrode).

• A. Heart complexes
• B. R waves
• C. Q waves
• D. S waves

Answer: (A)

In ECG interpretation, the size and direction of deflections in a given lead reflect how the heart’s electrical vectors project onto that lead’s axis. The ventricular depolarization vector—the main event represented by the QRS complex—produces the largest and fastest deflections. When the lead axis is aligned with the QRS axis, the ventricular vector points toward the positive electrode, giving the strongest, most positive deflection. Conversely, if the current flow is toward the negative electrode, that same vector projection becomes the most negative deflection.

So the strongest, most prominent deflections in this context are the heart complexes, i.e., the QRS complexes. They stand out because they reflect ventricular depolarization and are the largest deflections on the tracing. The other options don’t fit because the P wave reflects atrial depolarization (not ventricular), and the Q and S components are parts of the QRS morphology rather than the overall maximal positive deflection when the axis is parallel to the QRS axis.