Which EKG component indicates electrical activity preceding ventricular contraction?

The P wave represents the electrical activity associated with the depolarization of the atria, which occurs just before the ventricles contract. This initial phase of the cardiac cycle is crucial as it signals that the atria are contracting and pushing blood into the ventricles, setting the stage for ventricular contraction that follows. The P wave is therefore a key indicator of atrial electrical activity and precedes the QRS complex, where the ventricles depolarize and contract.

The other components noted in the options serve different purposes in the cardiac cycle. The QRS complex indicates ventricular depolarization, the ST segment represents the period between ventricular depolarization and repolarization, and the T wave reflects ventricular repolarization. Thus, while all these components are interconnected in the EKG, it is the P wave that specifically denotes the electrical activity prior to ventricular contraction.