Regional contribution of mitral annular dynamics to LV filling

Abstract

Mitral annular (MA) excursion is an established variable, related to both systolic and diastolic left ventricular (LV) function. MA excursion during diastole encompasses a volume that is part of the total LV filling, and altered excursion or area change of the MA may impair filling. We tested the hypothesis that LV inotropic state and loading condition alter regional LV filling properties. Six sheep underwent marker implantation in the LV wall and around the MA. After 7–10 days, biplane fluoroscopy was used to obtain 3-D marker dynamics during: 1) control conditions (CC), 2) after administration of calcium (C), 3) control conditions (NC), and 4) after administration of nitroprusside (N). Multiple tetrahedral volumes were calculated to measure the contribution of MA excursion and area change to LV filling. Compared with respectively control (mean±SD, *=p<0.05, **=p<0.01): 1) The contribution of MA dynamics to LV filling did not change with C (C: 3.2±0.9 vs. CC: 3.1±0.9 ml), but MA excursion increased (0.5±0.1** vs. 0.4±0.1 cm) and area decreased (6.4±0.7** vs. 7.4±0.7 cm2); 2) Total LV filling decreased with N (N: 15.4±4.6* vs. NC: 17.9±5.5 ml) without change in the absolute or relative contribution of MA dynamics to LV filling (3.0±0.7 vs. 3.7±1.1 ml) and (20.5±3.6 vs. 19.1±3.4 %) respectively, although MA mean area decreased (6.5±0.6** vs. 7.3±0.8 cm2). Although the mechanisms behind the contribution of MA dynamics to total LV filling change with inotropic state and loading condition, this component is robust and has substantial magnitude, accounting for approximately one-fifth of total LV filling.