Insufficiency may occur in each of the cardiac valves. Involvement of the pulmonary and tricuspid valves is much less common than involvement of the valves on the left side of the heart. Moreover, pulmonary insufficiency occurs only rarely as a primary disease. It is usually an incidental complication of pulmonary hypertension. Likewise, tricuspid insufficiency does not often occur as an isolated disturbance. It may complicate atrial septal defect, but more frequently is associated with significant rheumatic disease of the aortic and mitral valves. For these reasons I shall discuss only aortic and mitral insufficiency.
Incompetence at the Aortic Valve
The diastolic pressure of the systemic arterial system depends on (1) the volume of systemic flow in a given time, (2) the resistance to flow, and (3) the competence of the aortic valve. All other factors being equal, if the peripheral resistance is low, the diastolic pressure is low. Likewise, if