American Board of Cardiovascular Perfusion (ABCP) Board Practice Exam

The P wave of an EKG represents atrial systole, which is the phase of the cardiac cycle when the atria contract. During this time, the electrical impulse generated by the sinoatrial (SA) node leads to depolarization of the atria, resulting in their contraction and the subsequent flow of blood into the ventricles. The P wave visually reflects this electrical activity as a small upward deflection on the electrocardiogram. This contraction of the atria is crucial for filling the ventricles with blood before they contract during the next phase of the cardiac cycle. Understanding this relationship between the P wave and atrial systole is essential for interpreting EKG readings and assessing cardiac function.