The total QRS interval or R wave crest time in single leads is not accurate for measuring the total ventricular activation time, and is inadequate for an estimate of the ventricular activation rate, as related to the directional time rate of excitation of the total contributing muscle mass. For a more detailed and precise analysis of the ventricular activation, the angular speed in the central segment of the spatial QRS loop was determined in 103 normal men and 26 patients, and significant differences independent of the total QRS duration were obtained.