Atrial contraction follows atrial depolarization and results in
an increase in atrial pressure
As the atria contract, blood is pushed into the ventricles
Atrial contraction accounts for 10% to 30% of the end diastolic
ventricular volume, with the total contribution of
the atrial kick on ventricular volume dependent on venous
return and heart rate
Note that the ventricles remain in diastole during atrial
systole
