Timing of Surgery for Asymptomatic Primary Mitral Regurgitation: Possible Value of Early, Serial Measurements of Left Ventricular Sphericity

Abstract

Asymptomatic primary mitral regurgitation due to myxomatous degeneration of the mitral valve leaflets may remain so for long periods, even as left ventricular function progresses to a decompensated stage. During the early compensated stage, the ventricle's initial response to the volume overload is an asymmetric increase in the diastolic short axis dimension, accomplished by a diastolic shift of the interventricular septum into the right ventricular cavity, creating a more spherical left ventricular diastolic shape, increasing diastolic filling and stroke volume. Early valve repair is recommended to reduce postoperative left ventricular dysfunction. Early serial measurements of left ventricular sphericity index [LV-Si]. during the compensated stage of mitral regurgitation might identify subtle changes in left ventricular shape and assist in determining the optimal earliest timing for surgical intervention.

Keywords: diastolic filling.; left ventricular shape; left ventricular sphericity; myxomatous degeneration; primary mitral regurgitation; timing of mitral valve repair.

Fig. (1)

Cardiac shape in normal and MR contractions. Light lines are systole, and dark lines are diastole. (A) is normal. (B) shows change with MR: Note the diastolic shift of septum into RV, increasing LV end-diastolic volume.-In systole, the augmented septal contraction into the LV increases stroke volume and maintains cardiac output, despite the regurgitant volume loss. Source: Reprinted with permission from Am J Physiol 1996;271:H2689-700.Young AA, Orr R, Smaill BH, Dell'Italia LJ. Three-dimensional changes in left and right ventricular geometry in chronic mitral regurgitation with permission from The American Physiological Society.

Fig. (2)

(a). Schematic drawing of calculation of the 3D sphericity index. The LV cavity is shown, of which D is the LV end-diastolic major long axis. With the formula: [4/3∗π∗[D/2]³ a spherical volume in mL can be calculated, of which D is the diameter (cm). The 3D sphericity index is calculated as EDV/[4/3∗π∗[D/2]³. (b). Four-tile image display of the dynamic 3D dataset with two near perpendicular long axes (top panels), a short axis [lower left], and a cubical display with the corresponding cut planes (lower right). The measurement of D is shown. A prominent trabecula is present in the LV apex. Reprinted from Eur Heart J 2004;25:680-7). Mannaerts HF, van der Heide JA, Kamp O, Stoel MG, Twisk J, Visser CA. Early identification of left ventricular remodelling after myocardial infarction, assessed by transthoracic 3D echocardiography with permission from Oxford University Press.