The duration of atrial systole is:
0.80 second
0.57 second
0.11 second
0.44 second
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.