Varied onset of heart ventricular depolarization in different age groups of healthy volunteers.

Group mean isopotential maps of initial parts of ventricular depolarization (QRS complex) in 4 age groups (10, 14, 19 and 22 years) of young healthy subjects, females and males, were analyzed using different increments between isopotential lines. It was found that the increment 0.1 mV masks some features of the maps, which are seen only by smaller increment (0.02 mV): the time of appearance of maximum and minimum on the anterior chest, smaller voltage values of the extrema as usually published, minimum dominating over maximum in the youngest groups. Therefore, the often applied criterion for the QRS onset - the increasing maximum on the anterior chest - should be reconsidered at least when it concerns the isopotential maps of children.