What is the first positive deflection in the EKG?

In an electrocardiogram (EKG), the first positive deflection is the R wave. This occurs during the ventricular depolarization phase of the cardiac cycle and is part of the QRS complex. The QRS complex represents the electrical activity associated with the contraction of the ventricles.

To understand why the R wave is the first positive deflection, consider the structure of the QRS complex. It begins with the Q wave, which is the first negative deflection, followed by the R wave, which is the first positive deflection within that complex. After the R wave, the S wave occurs, which is another negative deflection that follows the R wave.

The T wave is associated with ventricular repolarization and occurs after the QRS complex. While it is a positive deflection, it is not the first one on the EKG. Thus, the R wave is identified as the initial positive deflection following ventricular depolarization, making it a key component in analyzing cardiac health and rhythm in EKGs.