In lead II of an EKG, what negative deflection indicates intraventricular septal depolarization?

In lead II of an EKG, the Q wave represents the initial negative deflection that occurs before the R wave. Specifically, this negative deflection indicates the depolarization of the interventricular septum, which is the wall separating the left and right ventricles of the heart.

During the normal conduction pathway, the impulse starts at the sinoatrial (SA) node, travels through the atria, and then moves rapidly to the ventricles via the bundle of His and the Purkinje fibers. As the electrical impulse spreads through the interventricular septum, it causes a downward deflection in the EKG, manifesting as the Q wave in lead II.

Identifying the depolarization of the interventricular septum is critical, as any abnormalities in this process can indicate various cardiac conditions, including myocardial infarction or conduction system disorders. The presence and morphology of the Q wave can give important diagnostic information about the heart's electrical activity and the health of the myocardium.