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. Each wave reflects different phases of electrical activity in the heart. A normal QRS duration is usually between 0.06 and 0.10 seconds. Abnormalities in the QRS complex can indicate various heart conditions, such as arrhythmias or myocardial infarction.