It is not hard to imagine that valve disease can be a major problem for the heart. In normal individuals it falls to approximately 80 mmHg before the valve opens again. Next, lets consider blood volume. With the onset of atrial contraction, volume increases a little more - to approximately 130ml. After closure of the mitral valve the volume in the ventricle is constant until the aortic valve opens - at which time ejection begins.
Ejection is initially rapid and continues until the aortic valve closes.
Note that ventricular volume at the time of closure is about 45 ml. Finally lets consider the ECG and Heart sounds. This brings about contraction of the ventricle. Before we discuss how CO is modulated during exercise let's first consider the results of such modulation. The necessity for increased output is evident from comparison of the distribution of CO at rest vs. during exercise, Table 1.