The following describes changes that occur in the left ventricular pressure-volume (PV) loop
when there is mitral stenosis
. Mitral stenosis (red PV loop in figure) impairs left ventricular filling so that there is a decrease in end-diastolic volume (preload
). This leads to a decrease in stroke volume (reduced width of PV loop) by the Frank-Starling mechanism
and a fall in cardiac output. Reduced ventricular filling and reduced aortic pressure decrease ventricular wall stress
), which may result in a small decrease in ventricular end-systolic volume; however, this is not sufficient to offset the reduction in end-diastolic volume. Therefore, because end-diastolic volume decreases more than end-systolic volume decreases, the stroke volume (shown as the width of the loop) decreases.
The changes described above and shown in the figure do not include cardiac and systemic compensatory mechanisms (e.g., systemic vasoconstriction, increased blood volume, and increased heart rate and inotropy) that attempt to maintain cardiac output and arterial pressure. Therefore, the red loop depicted in the figure only represents what may occur under a given set of conditions.