What is the first negative after a p wave in a normal cardiac cycle?

The first negative deflection after a P wave in a normal cardiac cycle is the Q wave, which is part of the QRS complex. The Q wave represents the initial depolarization of the interventricular septum and is typically a small downward deflection. It is followed by the R wave (upward deflection) and then the S wave (downward deflection), completing the QRS complex that corresponds to ventricular depolarization.