The duration of atrial systole is:

When the heart beats at a normal rate of 72/minute, duration of each cardiac cycle is about 0.8 second.  ATRIAL EVENTS  Atrial events are divided into two divisions:  Atrial systole = 0.11 (0.1) sec. Atrial diastole = 0.69 (0.7) sec.  VENTRICULAR EVENTS  Ventricular events are divided into two divisions:  Ventricular systole = 0.27 (0.3) sec  Ventricular diastole = 0.53 (0.5) sec.  In clinical practice, the term 'systole' refers to ventricular systole and 'diastole' refers to ventricular diastole. Ventricular systole is divided into two subdivisions and ventricular diastole is divided into five subdivisions.