The QRS complex is a key part of an electrocardiogram (ECG or EKG), which measures the electrical activity of the heart. It represents the rapid depolarization of the ventricles, the lower chambers of the heart, leading to their contraction. The QRS complex typically appears as a series of sharp spikes on the ECG trace and is crucial for assessing heart rhythm and function. The QRS complex consists of three distinct waves: the Q wave, the R wave, and the S wave. The Q wave is the first downward deflection, the R wave is the first upward spike, and the S wave is the following downward deflection. Analyzing the shape and duration of the QRS complex helps healthcare professionals identify various heart conditions, such as arrhythmias or myocardial infarctions.