<P> The QRS complex is a name for the combination of three of the graphical deflections seen on a typical electrocardiogram ( EKG or ECG ) . It is usually the central and most visually obvious part of the tracing . It corresponds to the depolarization of the right and left ventricles of the human heart . In adults , it normally lasts 0.06 -- 0.10 s ; in children and during physical activity , it may be shorter . The Q , R , and S waves occur in rapid succession , do not all appear in all leads , and reflect a single event , and thus are usually considered together . A Q wave is any downward deflection after the P wave . An R wave follows as an upward deflection , and the S wave is any downward deflection after the R wave . The T wave follows the S wave and , in some cases , an additional U wave follows the T wave . </P>
what is the heart doing during the qrs complex
depolarization of the right and left ventricles