What does an EKG primarily show?

An EKG, or electrocardiogram, primarily captures the electrical activity of the heart by recording the electrical potential differences that occur as the heart muscle depolarizes and repolarizes during each heartbeat. The EKG displays this activity using electrodes placed on the skin, which detect changes in voltage that occur as the electrical impulses travel through the heart. This method provides valuable insights into heart function, identifying arrhythmias, myocardial ischemia, and other cardiac conditions.

In contrast, the other options address different physiological aspects: blood flow pertains to hemodynamics and is evaluated through imaging techniques or Doppler studies; arterial pressure measurements involve sphygmomanometers and other devices that gauge the force of blood against artery walls; and blood chemical composition is assessed through laboratory tests that analyze blood samples for elements like glucose, electrolytes, and gases. Thus, the primary purpose of an EKG is to focus on the electrical signals of the heart, making the chosen answer the most accurate.