Determining the optimal time for surgical intervention in patients with chronic severe mitral regurgitation (MR) due to mitral valve prolapse (MVP) can present significant challenges, particularly in asymptomatic patients. When complex valve anatomy (anterior or bileaflet prolapse) precludes durable repair, close echocardiographic surveillance is recommended to ensure that should valve replacement become necessary, it be carried out in a timely fashion. Specifically, the 2014 American Heart Association/American College of Cardiology guidelines recommend that echocardiographic examination be performed every 1 to 2 years to ensure that the left ventricular (LV) ejection fraction does not fall to ≤60% or that the LV end-systolic dimension (LVESD) does not rise to ≥4.0 cm. Once either of these thresholds is crossed, postoperative LV systolic dysfunction becomes likely. These recommendations notwithstanding, it is our contention that reliance on LVESD for optimal surgical timing may be problematic, particularly in patients with marked leaflet redundancy or bileaflet flail. Here we describe what we believe are some of the potential problems that may be encountered in applying this measurement in such patients and suggest alternative approaches.
The 2015 American Society of Echocardiography chamber quantification guidelines recommend that measurement of LV internal dimensions be performed directly on a two-dimensional image in the parasternal long-axis view, perpendicular to the major axis at the point of leaflet coaptation ( Figure 1 ). To ascertain the correct position within the LV cavity where the LVESD should be measured, the anterior and apical excursion of the mitral valve coaptation point must be tracked through end-systole. LVESD is then measured one frame before mitral valve opening ( Figure 1 ). The practice of measuring the LVESD on M-mode recordings, in which the systolic excursion of the coaptation point cannot be tracked to its end-systolic position, is no longer recommended.
There are three determinants of the end-systolic position of the point of coaptation, and hence LVESD, in chronic severe MR due to MVP: (1) leaflet redundancy (geometry), (2) leaflet tethering, and (3) the LV closing force. Marked leaflet redundancy, as occurs with Barlow’s valve, can displace the mitral valve coaptation point basally toward the mitral annular plane, or even beyond it, into the left atrium, as depicted in Figures 2 and 3 . Such displacement may, however, be modulated by an apically directed leaflet tethering force that results from chronic LV volume overload and remodeling (enlargement), as well as by an opposing, basally directed, leaflet closing force generated by LV contraction. When the net effect of these competing influences moves the coaptation point closer to the annular plane, the measured LVESD increases because the diameter of the LV widens from apex to base.
