Which part of the EKG shows atrial contraction?

The part of the EKG that shows atrial contraction is the P wave. This wave represents the depolarization of the atria, which corresponds to the electrical activity that leads to atrial contraction. When the atria depolarize, they contract and push blood into the ventricles. The P wave is typically the first deflection on the EKG tracing, and its shape can provide information about atrial size and function.

In contrast, the other components of the EKG represent different phases of the cardiac cycle. The QRS complex follows the P wave and corresponds to the depolarization of the ventricles, which results in ventricular contraction. The T wave represents the repolarization of the ventricles, signaling the end of ventricular contraction and the beginning of the filling phase for the heart. Lastly, the U wave, although not always present, is thought to reflect the repolarization of the papillary muscles or the ventricles. Therefore, it is specifically the P wave that signifies the electrical activity associated with atrial contraction.