Three Waves Across The Ventricles Of The Human Heart

The image on an EKG made up of three waves is called the QRS complex. The Q wave is the first negative deflection (below the isoelectric line), the R wave which is the first upward or positive deflection, and the S wave is the next negative deflection immediately after the R wave. This indicates contraction of the ventricles. The normal QRS interval is between 0.08 to 0.10 seconds. It corresponds to the depolarization of the right and left ventricles of the human heart. Normal QRS complex width is 70-100ms. The QRS width is useful in determining the origin of each QRS complex (eg. Sinus, atrial, junctional, or ventricular). Narrow complexes (QRS100ms) may be either ventricular in origin, or may be due to aberrant conduction of supraventricular