Which ECG component indicates the heart is preparing for contraction?

The QRS complex is the component of an ECG that indicates the heart is preparing for contraction. This complex represents the rapid depolarization of the ventricles, which is the process that leads to ventricular contraction. During this phase, the electrical impulses travel through the ventricles, signaling them to contract and pump blood throughout the body.

In contrast, the P wave reflects atrial depolarization, which occurs prior to ventricular contraction. The T wave represents the repolarization of the ventricles, marking the period when the ventricles are recovering from contraction and preparing for the next heartbeat. The U wave is less commonly seen but is related to repolarization and can indicate specific conditions, but it does not directly indicate preparation for contraction. The QRS complex’s clear association with ventricular depolarization and subsequent contraction is why it is recognized as the component indicating the heart is getting ready to contract.