Variability and diversity of the electrical cardiac systole.

The electrical cardiac systole originates from the beginning of the P wave (atrial depolarisation) until the end of the downward branch of the T wave (ventricular repolarisation). It includes, therefore, succession P-QRS-T and its corresponding intervals and segments: PQ, ST, and QT. The mathematical possibilities of variability in the length of the electrical systole of the heart may be diverse. It is well documented and established that such changes in length may make the myocardial cells more vulnerable and unstable, and may also cause serious cardiac arrhythmias and even sudden death. The current presentation illustrates these electrocardiographic entities with significant variations in the length of its waves and intervals: short PQ and QT intervals, short PQ and long QT, long PQ and long QT. All parameters appeared in young adult males.