Answer to Question 1
At the end of ventricular diastole, both atria simultaneously contract to eject 10 to 30 more blood into the ventricles.
Answer to Question 2
During pacing, the cardiac monitor is observed for electrical capture, usually evidenced by a wide QRS and broad T wave. In some patients, electrical capture is less obvious, indicated only as a change in the shape of the QRS. Mechanical capture is evaluated by assessing the patient's right upper extremity or right femoral pulses.