Dissociation of end systole from end ejection in patients with long-term mitral regurgitation

To determine whether left ventricular (LV) end systole and end ejection uncouple in patients with long-term mitral regurgitation, 59 patients (22 control patients with atypical chest pain, 21 patients with aortic regurgitation, and 16 patients with mitral regurgitation) were studied with micromanometer LV catheters and radionuclide angiograms. End systole was denned as the time of occurrence (T_max) of the maximum time-varying elastance (E_max), and end ejection was defined as the time of occurrence of minimum ventricular volume (minV) and zero systolic flow as approximated by the aortic dicrotic notch (Aodi). The temporal relation between end systole and end ejection in the control patients was T_max (331±42 [SD] msec), minV (336±36 msec), and then, zero systolic flow (355±23 msec). This temporal relation was maintained in the patients with aortic regurgitation. In contrast, in the patients with mitral regurgitation, the temporal relation was T_max (266±49 msec), zero systolic flow (310±37 msec, p<0.01 vs. T_max), and then, minV (355±37 msec, p<0.001 vs. T_max and p<0.01 vs. Aodi). Additionally, the average T_max occurred earlier in the patients with mitral regurgitation than in the control patients and patients with aortic regurgitation (p<0.01, for both), whereas the average time to minimum ventricular volume was similar in all three patient groups. Moreover, the average time to zero systolic flow also occurred earlier in the patients with mitral regurgitation than in the control patients (p<0.01) and patients with aortic regurgitation (p<0.05). Because of the dissociation of end systole from minimum ventricular volume in the patients with mitral regurgitation, the end-ejection pressure-volume relations calculated at minimum ventricular volume did not correlate (r= -0.09), whereas those calculated at zero systolic flow did correlate (r= 0.88) with the E_max slope values. We conclude that end ejection, denned as minimum ventricular volume, dissociates from end systole in patients with mitral regurgitation because of the shortened time to LV end systole in association with preservation of the time to LV end ejection due to the low impedance to ejection presented by the left atrium. Therefore, pressure-volume relations calculated at minimum ventricular volume might not be useful for assessing LV chamber performance in some patients with mitral regurgitation.