Depends on the speed of onset and severity of mitral regurgitation.
If, for example, there is acute regurgitation into a small left atrium then this is associated with a large systolic pressure wave and consequent pulmonary oedema.
If however there is chronic regurgitation then there is an opportunity for there to be compensatory left ventricular and atrial dilatation with little increase in pressure (although it is usual for there to be a dominant systolic wave in the left atrium). In this case the decrease in ejection fraction is delayed.
Last reviewed 01/2018