r waves definition in ecg
P wave- the arch preceding the QRS complex. Q wave- the first negative (downward) deflection of the complex. In some leads, it will not be present. In some cases, the complex begins with an R wave. R wave- the first positive (upward) deflection of the QRS complex. It will sometimes be preceded by a Q wave. S wave- any negative (downward) deflection following an R wave. T wave- the arch following the QRS complex.