Mitral Stenosis
The following describes changes that occur in the left ventricular
pressure-volume loop when there is
mitral stenosis. Mitral
stenosis (red pressure-volume 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
by the
Frank-Starling mechanism and a fall in cardiac output and aortic
pressure. This reduction in
afterload
(particularly aortic diastolic pressure) enables the end-systolic volume to
decrease slightly, but not enough to overcome the decline 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.
Revised 04/05/07
