Isovolumetric Relaxation.
It has been previously explained that during this badly named period,
the whole heart does not relax but rather the AS contracts., There are
records where the opening of the mitral valve begins with the unwinding
and elongation of the LV (even with the aortic valve open) during this
period, 50% to 60% of recoil and detorsion occur, promoting a drop in
LV pressure below left atrial pressure, conditioning explosive LV
suction, the interdependence of twisting and recoil is an essential
interaction39, because twisting must stop before
unwinding can begin. When an increase in DS contraction torsion occurs
and isovolumetric relaxation time is prolonged, as in aortic stenosis,
hypertension, and ischemia, diastolic dysfunction can
develop40.